bluuebunny/crossref_metadata_2025_split huggingface dataset:
Differentiation of Boc‐ α,β‐ and β,α‐peptides and a pair of diastereomeric β,α‐dipeptides by positive and negative ion electrospray tandem mass spectrometry (ESI‐MS/MS)
Authors: Reddy P. Nagi , Srikanth R. , Swamy N. S. , Srinivas R. , Sharma G. V. M. , Nagendar Pendem , Krishna Palakodety Radha 
Published: October 2005

AbstractPositive and negative ion electrospray ionization (ESI) tandem mass spectral study of a new series of hybrid peptides, viz, BocN‐α,β‐peptides and BocN‐β,α‐peptides, synthesized from C‐linked carbo‐β3‐amino acids [Caa (S)] and L‐Ala has been carried out. The α,β‐peptides have been differentiated from β,α‐peptides by the collision‐induced dissociation (CID) of [M + H]+ and [M − H]− ions in positive and negative ion ESI‐MS respectively. The fragment ion [M + H − C(CH3)3 + H]+ formed from [M + H]+ ions by the loss of 2‐methyl‐prop‐2‐ene in α,β‐peptides with L‐Ala at the N‐terminus is insignificant or totally absent for β,α‐peptides which have the Caa (S) at N‐terminus. The fragment ion [M − H‐C(CH3)3OH − HNCO]− formed from [M − H]− of β,α‐peptide acids is totally absent for α,β‐peptide acids. This has been attributed to the absence of the β‐methylene group in α,β‐peptides, and the participation of the β‐methylene group in the loss of HNCO in β,α‐peptide acids is confirmed by the deuteration experiments. The CID of [M + H‐Boc + H]+ ions of these peptides also produce characteristic fragmentation. In the CID spectra of α,β‐peptides, the bn+ ions and the resulting yn+ ions occur at a mass difference of 243 and 71 Da corresponding to the successive losses of Caa and L‐Ala, whereas a mass difference of 71 and 243 Da is observed for β,α‐peptides. In contrast to the CID of protonated peptides, the CID of [M − H]− ions of the α,β‐ and β,α‐peptide acids do not give bn− ions and show abundant zn− ions. Further, a pair of diastereomeric dipeptide esters and acids have been distinguished by the CID of [M + H]+ ions. The loss of 2‐methyl‐prop‐2‐ene is more pronounced for Boc‐NH‐Caa(R)‐D‐Ala‐OCH3 (21) and Boc‐NH‐Caa(R)‐D‐Ala‐OH (23) with Caa (R) at the N‐terminus, whereas it is totally absent for Boc‐NH‐Caa (S)‐D‐Ala‐OCH3 (22) and Boc‐NH‐Caa(S)‐D‐Ala‐OH (24) peptides, which have Caa (S) at the N‐terminus. Thus, on the basis of our previous and present studies, we propose that the CID of [M + H]+ ions provides a simple and useful method for distinguishing the configuration of Caa (S or R) at the N‐terminus of BocN‐carbo β,α‐ and β,β‐dipeptides. Copyright © 2005 John Wiley & Sons, Ltd.
Separation and online preconcentration by multistep stacking with large‐volume injection of anabolic steroids by capillary electrokinetic chromatography using charged cyclodextrins and UV‐absorption detection
Authors: Urban Pawel L. , García‐Ruiz Carmen , García Ma Ángeles , Marina Ma. Luisa 
Published: October 2005

AbstractThe separation of three common anabolic steroids (methyltestosterone, methandrostenolone and testosterone) was performed for the first time by capillary EKC. Different charged CD derivatives and bile salts were tested as dispersed phases in order to achieve the separation. A mixture of 10 mmol/L succinylated‐β‐CD with 1 mmol/L β‐CD in a 50 mmol/L borate buffer (pH 9) enabled the separation of the three anabolic steroids in less than 9 min. Concentration LODs, obtained for these compounds with low absorption of UV light, were ~5×10–5 mol/L. The use of online reverse migrating sample stacking with large‐volume injection (the effective length of the capillary) enabled to improve the detection sensitivity. Sensitivity enhancement factors (SEFs) ranging from 95 (for testosterone) to 149 (for methyltestosterone) were achieved by single stacking preconcentration. Then, the possibilities of multistep stacking to improve the sensitivity for these analytes were investigated. SEFs obtained by double stacking preconcentration ranged from 138 to 185, enabling concentration LODs of 2.79×10–7 mol/L (for methyltestosterone), 3.47×10–7 mol/L (for testosterone) and 3.56×10–7 mol/L (for methandrostenolone). Although online triple stacking preconcentration was achieved, its repeatability was very poor and SEFs for the studied analytes were not calculated.
Determination of some polycyclic aromatic hydrocarbons in filter tar of Turkish cigarettes
Authors: Aygün Seker Fatma 
Published: October 2005

AbstractA simultaneous determination method for the analysis of benzo[a]pyrene (BaP) and dibenzo[a,h]anthracene (DahA) in the filter tar of Turkish cigarettes has been developed. The method involved (a) the extraction of BaP and DahA with n‐hexane from ACN solution in which the cigarette filters were extracted, and then (b) purification of the n‐hexane extracts by elution on an XAD‐2 column using n‐hexane/dichloromethane (9 : 1, v/v) mixture. Separation and quantitative determination of BaP and DahA in the extracts were carried out by HPLC and fluorescence detection on a C18 RP column. The calculated recoveries for BaP and DahA were found in the range of 90–100% for each extraction and clean‐up steps. Analysis of various filter tar of Turkish cigarettes showed that an average of 74.28 ng/filter of BaP and 5.24 ng/filter of DahA were present in Turkish cigarettes.
Chain Growth Polycondensation as a Polymer Generating Reaction in the Synthesis of Oligo(p‐phenyleneethynylene)s with Low Polydispersity
Authors: Kovalev Aleksey I. , Takeuchi Kazuhiko , Barzykin Alexander V. , Asai Michihiko , Ueda Mitsuru , Rusanov Alexander L. 
Published: October 2005

AbstractSummary: The polycondensation of 1‐ethynyl‐2,5‐dihexyl‐4‐iodobenzene in the presence of 1‐ethynyl‐2,5‐dihexyl‐4‐(2‐phenylethynyl)benzene proceeds according to the mechanism of initiated chain growth polycondensation. It has allowed the synthesis of oligomers with a desired molecular weight and a narrow molecular weight distribution. The reasons for the side reaction leading to the formation of diyne compounds are revealed and the presumed mechanism is given. This opens prospects for the preparation of defectless poly(p‐phenyleneethynylene)s with required molecular weights and narrow molecular weight distributions.
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Syncope in children with Tourette's syndrome treated with guanfacine
Authors: King Allison , Harris Peter , Fritzell James , Kurlan Roger 
Published: October 2005

AbstractWe report on 4 children who experienced a syncopal episode while being treated with guanfacine without any other evident cause. Syncope appears to be an uncommon side effect of guanfacine and is probably due to drug‐induced hypotension or bradycardia. © 2005 Movement Disorder Society
Non‐homogeneous non‐linear damped wave equations in unbounded domains
Authors: Racke Reinhard 
Published: October 2005

AbstractWe present a global existence theorem for solutions of utt − ∂iaik (x)∂ku + ut = ƒ(t, x, u, ut, ∇u, ∇ut, ∇2u), u(t = 0) = u0, u(=0)=u1, u(t, x), t ⪖ 0, xϵΩ.Ω equals ℝ3 or Ω is an exterior domain in ℝ3 with smoothly bounded star‐shaped complement. In the latter case the boundary condition u|∂Ω = 0 will be studied. The main theorem is obtained for small data (u0, u1) under certain conditions on the coefficients aik.The Lp ‐ Lq decay rates of solutions of the linearized problem, based on a previously introduced generalized eigenfunction expansion ansatz, are used to derive the necessary a priori estimates.
Vector spherical spline interpolation—basic theory and computational aspects
Authors: Freeden Willi , Gervens Theo 
Published: October 2005

AbstractVector spherical interpolation is discussed from both the theoretical and computational points of view. The theory of vector spherical harmonics is an essential tool. An estimate is given for the absolute error of the interpolation process; an efficient algorithm is developed for the computation of a vector spherical interpoiant. The displacement boundary value problem of determining the elastic field from a finite number of discretely given displacement vectors is solved by the use of vector splines.
An implicit finite‐difference algorithm for the numerical simulation of supersonic flow over blunted bodies
Authors: El‐Seoud S. Abou , Törnig W. 
Published: October 2005

AbstractIn order to compute axisymmetric laminar supersonic flow we use an unsteady implicit finite‐difference scheme. This scheme solves numerically either the inviscid Euler equations or the ‘thin‐layer’ Navier‐Stokes equations. In both cases the scheme leads to large sparse non‐linear systems, which can be solved by a genuine iteration process. The convergence of this process is shown and numerical results are given.
Numerical analysis of semi‐linear parabolic systems in diffusion–reaction problems
Authors: Fayyad D. , Nassif N. 
Published: October 2005

AbstractIn this paper, we investigate problems of approximation for the solution of a system of coupled semi‐linear parabolic partial differential equations that model diffusion‐reaction problems in chemical engineering. Given that the solutions belong to Hs (0, ∞), we consider finite‐element approximations on bounded domains (0, R(h)) such that limh→0[R(h)] = ∞. Optimal convergence estimates are found to depend on the asymptotic behaviour of the solution and its regularity near t = 0. In the L2‐norm, they cannot exceed an order of O((;h2/t3/4) + h2[In h]2). For that purpose, a Wheeler‐type argument is also generalized to non‐coercive elliptic forms. Fully discrete schemes that preserve the positivity of the solutions are also considered. Due to the singularity at t = 0, they lead to estimates of the order O(τ1/4 + h2/t3/4).
Local compactness for linear elasticity in irregular domains
Authors: Weck Norbert 
Published: October 2005

AbstractFor the theory of boundary value problems in linear elasticity, it is of crucial importance that the space of vector‐valued L2‐functions whose symmetrized Jacobians are square‐integrable should be compactly embedded in L2. For regions with the cone property this is usually achieved by combining Korn's inequalities and Rellich's selection theorem. We shall show that in a class of less regular regions Korn's second inequality fails whereas the desired compact embedding still holds true.
Best constants in Korn‐Poincaré's inequalities on a slab
Authors: Ito Hiroya 
Published: October 2005

AbstractWe establish the best constants in the Poincaré‐type and the trace‐type inequalities for the quadratic form \documentclass{article}\pagestyle{empty}\begin{document}$ \lambda ||\,{\rm div}\,{\rm u}\,||_{L^2 }^2 \, + \,2\,\mu \,||\,\,(\nabla {\rm u}\, + \,\nabla {\rm u}^{\rm T})/2\,||_{L^2 }^2 $\end{document} which is fundamental in elasticity theory, on the space of H1 vector fields u on a slab vanishing on one or both of its sides. We similarly calculate those constants for the case of H1 divergence‐free vector fields. Our method, which is fairly general, has another practical application to the quadratic form ∑j,k(ajk∂ku, ∂ju)L2 with coefficients a jk = akj ε C in H1 scalar functions u on a slab.
A generalization of the H‐theorem to steady non‐equilibrium states. Part 1: A basic decomposition and the linear case
Authors: Triolo L. 
Published: October 2005

AbstractA generalized relative entropy functional is associated to the evolution of gas in a container with (generally) non‐uniform boundary data. A decomposition for its rate in ‘bulk’ and in ‘boundary’ terms is given; for the linear case both have a definite sign. The relation with the strong L1 stability is pointed out.
Regularising discretizations of the Birkhoff‐Rott equation
Authors: Friedrich Oliver , Sonar Thomas 
Published: October 2005

AbstractA thin shear layer moving from the trailing edge of a two‐dimensional aerofoil section downstream can be interpreted as a curve of discontinuity for the tangential velocity and may be approximated by a vortex sheet in inviscid, incompressible fluid flow. It is well known that vortex sheets are subject to instabilities of Kelvin‐Helmholtz type which lead to roll‐up phenomena in the wake. The motion of such sheets is governed by the Birkhoff‐Rott equation. In the case of Kelvin‐Helmholtz instability it seems clear that a curvature singularity occurs at a certain critical time and that consistent discretizations of the Birkhoff‐Rott equation may fail to yield reliable results even before the time of occurrence of a singularity. We discuss the modification of the Biot‐Savart kernel in the sense of Krasny who regularized the kernel by means of a global parameter. Using discrete Fourier transform we show the damping influence of this regularization technique. We modify the kernel carefully by introducing a regularization found in ordinary vortex methods and show that reliable results may be obtained up to and slightly after the singularity formation without increasing the accuracy of the computation.
Cloned endangered species takin (Budorcas taxicolor) by inter‐species nuclear transfer and comparison of the blastocyst development with yak (Bos grunniens) and bovine
Authors: Li Yanxin , Dai Yunping , Du Weihua , Zhao Chunjiang , Wang Haiping , Wang Lili , Li Rong , Liu Ying , Wan Rong , Li Ning 
Published: October 2005

AbstractInterspecies cloning might be used as an effective method to conserve endangered species and to support the study of nuclear–cytoplasm interaction. In this study, we describe the development of takin–bovine embryos in vitro produced by fusing takin ear fibroblasts with enucleated bovine oocytes and examine the fate of mitochondrial DNA in these embryos. We also compare the blastocyst development of takin–bovine embryos with yak–bovine and bovine–bovine embryos and compare the cell numbers of the blastocyst. Our results indicate that: (1) takin–bovine cloned embryos can develop to the blastocyst stage in vitro (5%), (2) blastocyst mitochondria DNA are derived primarily from bovine oocytes in spite of a little takin donor cell mitochondrial DNA, (3) using the same cloned protocol, development efficiency is significantly different between bovine–bovine cloning, yak–bovine, and takin–bovine cloning (48 vs. 28% vs. 5%, P < 0.01), and (4) cell numbers in the blastocysts of the three species of embryos were not different. These results suggest that the bovine oocytes can reprogram the takin, yak, and bovine fibroblast nuclei. However, the development efficiency of intra‐species cloning tends to be higher than inter‐species cloning; the more close the species of the donor cell is to the recipient oocyte (yak versus takin), the greater the blastocyst development in vitro. Mol. Reprod. Dev. © 2005 Wiley‐Liss, Inc.
Morphological effects of myasthenia gravis patient sera on human muscle cells
Authors: Luckman Steven Paul , Skeie Geir Olve , Helgeland Geir , Gilhus Nils Erik 
Published: October 2005

AbstractMyasthenia gravis (MG) is caused primarily by autoantibodies against the nicotinic acetylcholine receptor (AChR), but autoantibodies to other muscle proteins may be present. Many of these proteins have structural or signalling functions, the disruption of which may affect muscle cell morphology or viability. In order to investigate the role of such autoantibodies in MG, we examined the effect of MG patient sera, of different autoantibody composition and obtained at different stages of disease severity, on primary human muscle cells. Sera from MG patients induced changes in cell morphology from typical elongated cells to an irregular phenotype, caused the formation of inclusion bodies and intracellular vesicles, and led to a disordered arrangement of actin microfilaments. Sera from the most severely affected patients also induced cell death, which did not occur via classic apoptosis. The effects were not complement‐mediated and were dose‐ and time‐dependent. As the effects observed in the cell culture system correlated with disease severity, a greater understanding of the individual factors responsible for these effects may improve our understanding of MG pathogenesis and be of value in the assessment of disease in individual patients. Muscle Nerve, 2005
Comparison of the urethral properties of the female guinea pig and rat
Authors: Walters Richard David , McMurray Gordon , Brading Alison Frances 
Published: October 2005

AbstractAimsThe main focus of this study was to profile and compare urethral function in the female guinea pig and rat, and to characterize urodynamically distinctive patterns in the micturition cycle of the two species. This exercise aimed to investigate potential species‐related differences and determine a suitable animal model for the human urethra.Materials & MethodsFemale Dunkin–Hartley guinea pigs (400–500 g) and Sprague‐Dawley rats (200–300 g) were used throughout the study. For in vitro experiments urethral rings were suspended vertically for isometric tension recording in 5 ml organ baths and drugs (phenylephrine 10−4 M and carbachol 10−4 M) were applied directly to the bathing solution. In vivo urethral pull‐through and urodynamic studies were performed under urethane anesthesia, and phenylephrine (200 µg/kg) was administered during urethral pull‐through experiments via the intravenous (i.v.) route. Urethral, bladder and arterial pressures, and external urethral sphincter electromyographic (EMG) spike activity were recorded simultaneously throughout.ResultsOrgan bath studies coupled with in vivo pull‐through experiments produced urethral profiles with distinct regional variations for both species. Urodynamic studies with the urethral probe fixed in the high pressure zones of the proximal urethra produced similar recordings in both species during bladder filling and marked differences during micturition. The guinea pig showed complete sphincteric inhibition immediately prior and during micturition as also seen in the human, whereas the rat exhibited high frequency bursts in EMG activity at this stage in the cycle.ConclusionsThe EMG activity seen in the rat during micturition is presumably necessary for efficient voiding, thus the guinea pig is a more suitable comparative model for the human in relation to urethral properties during micturition. Neurourol. Urodynam. © 2005 Wiley‐Liss, Inc.
A comparison of some domain decomposition and ILU preconditioned iterative methods for nonsymmetric elliptic problems
Authors: Cai Xiao‐Chuan , Gropp William D. , Keyes David E. 
Published: October 2005

AbstractIn recent years, competitive domain‐decomposed preconditioned iterative techniques of Krylov‐Schwarz type have been developed for nonsymmetric linear elliptic systems. Such systems arise when convection‐diffusion‐reaction problems from computational fluid dynamics or heat and mass transfer are linearized for iterative solution. Through domain decomposition, a large problem is divided into many smaller problems whose requirements for coordination can be controlled to allow effective solution on parallel machines. A central question is how to choose these small problems and how to arrange the order of their solution. Different specifications of decomposition and solution order lead to a plethora of algorithms possessing complementary advantages and disadvantages. In this report we compare several methods, including the additive Schwarz algorithm, the classical multiplicative Schwarz algorithm, an accelerated multiplicative Schwarz algorithm, the tile algorithm, the CGK algorithm, the CSPD algorithm, and also the popular global ILU‐family of preconditioners, on some nonsymmetric or indefinite elliptic model problems discretized by finite difference methods. The preconditioned problems are solved by the unrestarted GMRES method. A version of the accelerated multiplicative Schwarz method is a consistently good performer.
Thermal stress evaluation in the steel continuous casting process
Authors: Risso J. M. , Huespe A. E. , Cardona A. 
Published: October 2005

AbstractTwo numerical models for the thermal stress and plastic strain analysis in the solid shell at the initial stage of a steel continuous casting process, are presented and their performances evaluated. First, a numerical procedure based on a natural extension of the semi‐analytical study proposed by Weiner and Boley (J. Mech. Phys. Solids 1963; 11:145–154) is introduced and validated by comparison with their semi‐analytical 1‐D solution. The basic hypotheses of this model, and particularly the extended plane strain condition with uniform axial strain, are afterwards tested in more complex and realistic situations by comparing results with those obtained by an alternative numerical scheme presented by Fachinotti (Doctoral Thesis, Universidad Nac. Litoral, Argentina, 2001) and Fachinotti and Cardona (Internal Report, CIMEC, sent to IJNME, 2002). Finally, results of a typical and representative 3D simulation, corresponding to a slab continuous casting process, are shown. Copyright © 2005 John Wiley & Sons, Ltd.
Trefftz solutions for piezoelectricity by Lekhnitskii's formalism and boundary‐collocation method
Authors: Sheng N. , Sze K. Y. , Cheung Y. K. 
Published: October 2005

AbstractIn this paper, a solution procedure for plane piezoelectricity is developed by Trefftz boundary‐collocation method. Starting with the general plane piezoelectricity solution derived by Lekhnitskii's formalism, the basic sets of Trefftz functions which satisfy the homogeneous governing equations are derived. Moreover, special sets of Trefftz functions are derived for impermeable elliptical voids, impermeable sharp cracks and permeable sharp cracks with arbitrary orientations with respect to the material poling direction. The functions in the special sets satisfy not only the homogeneous governing equations but also the boundary conditions at the peripheries of the pertinent defects. By adopting Trefftz functions as the trial functions, multi‐domain Trefftz boundary‐collocation method is formulated. Numerical examples are presented to illustrate the efficacy of the formulation. Copyright © 2005 John Wiley & Sons, Ltd.
A generalized non‐linear transformation for evaluating singular integrals
Authors: Yun Beong In 
Published: October 2005

AbstractIn this paper, we propose a function which, according to a parameter included therein, generates a new sigmoidal transformation and converges to the well‐known Sato polynomial transformation. Following well‐established procedures in the literature, we employ the present transformation in the numerical evaluation of weakly singular integrals, Cauchy principal value integrals and Hadamard finite‐part integrals.By several numerical examples it is shown that the present transformation is available for all kinds of singular integrals mentioned above and, in some cases, gives better results compared with those of traditional non‐linear transformations. Copyright © 2005 John Wiley & Sons, Ltd.
An iterative procedure for the oscillatory laminar boundary layer
Authors: Newton S. G. 
Published: October 2005

AbstractThe problem of small sinusoidal oscillations imposed on a stagnation point flow is considered. This leads to an ordinary differential equation which, in the high frequency limit, has a simple solution. An iterative method (involving a linear integral operator) is developed, starting from this basic solution. This scheme, performed numerically, is ‘under‐relaxed’ and this renders it applicable to as wide a frequency range as possible: convergence criteria are discussed in terms of the relaxation parameter. The streamwise velocity profiles computed are compared with those given by an independent method.