bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of quantum mechanical perturbative sums in terms of quadratic surds and their use in the approximation of ζ(3)/π3
Authors: Bracken Paul , Čížek Jiri 
Published: October 2002

AbstractThe first correction to the energy using Rayleigh–Schrödinger perturbation theory is calculated for the ground state of the one‐dimensional Hubbard model. An algebraic technique is developed which can be used to evaluate these perturbative sums such that the final result is expressed as a finite linear combination of the elements which occur in the individual terms of the sum. The first nontrivial correction to the energy for the ground state of the one‐dimensional Hubbard model in closed form is evaluated. A number theoretic application of this calculation will be given, which is related to the Euclidean construction of regular polygons inside the circle. It is shown that ζ(3) can be approximated by a product of nested radicals and rational constants, multiplied by π3, much in the same way that ζ(2) was expressed by Euler as a product of rational numbers and π2. It is discussed how this analysis can be continued to higher orders in perturbation theory such that ζ(2m+1) is obtained as a multiple of π2m+1 and nested radicals. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Structure and self‐energy of the electron
Authors: Blinder S. M. 
Published: October 2002

AbstractThe region very close to an electron (r≲r0=e2/mc2≈2.8×10−13 cm) is, according to quantum electrodynamics, a seething maelstrom of virtual electron–positron pairs flashing in and out of existence. To take account of this well‐established physical reality, a phenomenological representation for vacuum polarization is introduced into the framework of classical electrodynamics. Such a model enables a consistent picture of classical point charges with finite electromagnetic self‐energy. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Polarization potential for e‐argon scattering by differential scattering minimization at intermediate energies
Authors: Paikeday Joseph M. , Alexander Jason 
Published: October 2002

AbstractThe differential scattering cross section (DCS) for electrons scattered elastically by argon atoms is studied using a model potential. In the present study the long range polarization potential is represented by an energy‐dependent function in the form Vp(E,r)=αd/[r+ξ(a,b,E)]4 and the short range part is constructed from the nonrelativistic Hartree–Fock wave function of the target atom in the form Vs(r)=(2Z/r)∑nCnexp {−nC0r}. Accurate phase shifts have been computed for angular momentum in the range 0<ℓ<13 from the Schrödinger equation and the Born approximation for higher values of ℓ<1000. The computed differential cross section obtained using the approximate effective interaction potential for electrons scattered by the target atoms in their ground state is compared with available published results. In the present study the parameters contained in the energy‐dependent polarization potential are determined by the minimization of the DCS with respect to angle θ and the incident energy of E. The critical values of angle and energy (θc,Ec) are found to be (117.3°, 120.0 eV), (64.1°, 41.3 eV), and (140.1°, 37.3 eV). The resulting DCS in the angular range 2°<θ<178° is found to be an improvement over earlier results and in better agreement with the available experimental data in the intermediate energy range. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Recurrent generation of approximate functionals in density functional theory*
Authors: Liu Shubin 
Published: October 2002

AbstractThe idea of recurrent generation of approximate exchange–correlation energy density functionals in density functional theory is investigated and evaluated in this article through the so‐called Levy transformation, which enables one to obtain the exact exchange correlation energy without knowing the details of its kinetic energy component. Although in principle the transformation is valid only for exact functionals, it is argued that approximate functionals may also be applied and then recurrently used. As a demonstration of the idea, a generalized form of the Wigner‐type functional is introduced and transformed into polylogarithm functionals. Numerical illustrations of examples show that for local functionals, better results may be yielded after the transformation, whereas for nonlocal functionals, identical results have been obtained for n≥2 transformations. In addition, two nonlocal approximate functionals beyond the generalized gradient approximation (GGA) are proposed which show better performance in energetics over GGA functionals. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
QR–SCMEH–MO calculations on NdO and UO
Authors: Boudreaux Edward A. , Baxter Eric 
Published: October 2002

AbstractElectronic structures and chemical bonding within the NdO and UO molecules have been studied computationally via the QR–SCMEH–MO (quasirelativistic–self‐consistent modified extended Hückel–molecular orbital) method. This is a non‐ab initio, self‐consistent, nonempirical routine that accounts for correlation in an approximate way. It also incorporates other features so as to account for all electron interactions. Both molecules were found to be bonding [contrary to a report based on ab initio density functional theory (DFT)–SCF relativistic calculations on UO]. The covalency in UO is somewhat greater than that of NdO, which for all practical purposes is mostly electrostatic. Good agreement between calculated and observed bond dissociation energies and ionization potentials have been obtained. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Intermolecular perturbation theory applied to an exactly solvable model
Authors: Adams William H. 
Published: October 2002

AbstractIt is remarkable that application of intermolecular perturbation theory to a simple, exactly solvable model of diatomic molecules reproduces the basic problems encountered when that theory is applied to real systems. For real systems it took over 50 years to recognize fully the consequences of choosing products of atomic/molecular functions as unperturbed wave functions. The primary consequence is that the physical ground state energy is generally buried in a continuum of unphysical state energies, i.e., energies of states which violate the Pauli Exclusion Principle. This makes the simplest perturbation theory incapable of predicting even the ground state energy of most systems when summed to infinite order. The model reveals clearly why and how unphysical solutions arise in intermolecular perturbation theory. The model neglects the interaction between electrons, reducing the N‐electron problem to that of the one‐electron molecular ion. Because the model can be solved exactly, it is suggested that it could be useful in testing new perturbation theories for the calculation of intermolecular potential surfaces. The traditional test systems, H2+ and H2, provide no real test because they have no unphysical solutions. © 2002 John Wiley & Sons, Inc. Int J Quantum Chem, 2002
Calculation of nuclear‐attraction and modified overlap integrals using Gegenbauer coefficients*
Authors: Öztekin E. , Özcan S. , Orbay M. , Yavuz M. 
Published: October 2002

AbstractThe modified overlap and nuclear‐attraction integrals over Slater‐type orbitals are calculated for extremely large quantum numbers using Gegenbauer coefficients and basic overlap integrals. The accuracy of the results is quite high for the principal quantum numbers of Slater functions and for arbitrary values of internuclear distances and screening constants of atomic orbitals. © 2002 John Wiley & Sons, Inc. Int J Quantum Chem, 2002
Rapid method for determination of chlormequat residues in tomato products by ion‐exchange liquid chromatography/electrospray tandem mass spectrometry
Authors: Careri M. , Elviri L. , Mangia A. , Zagnoni I. 
Published: October 2002

AbstractA rapid method has been devised for the direct determination of chlormequat in tomato samples. No clean‐up is required, and analysis uses ion‐exchange liquid chromatography/tandem mass spectrometry interfaced with electrospray ionization (LC/ESI‐MS/MS). A cation‐exchange column was used with an aqueous ammonium acetate/acetonitrile mixture as the mobile phase under isocratic conditions. The method was validated in terms of detection limits (LOD), quantitation limits (LOQ), linearity, recovery, precision and accuracy. Good results in the low µg kg−1 level were obtained for the LOD and LOQ of chlormequat in tomato samples. Comparison of solvent and matrix‐matched calibration curves demonstrated the absence of significant matrix effects and the feasibility of using external calibration. Linearity was established over two orders of magnitude by performing homoscedasticity and Mandel fitting statistical tests. The absence of both constant and proportional systematic errors was verified by evaluating the recovery function, demonstrating good method accuracy. Excellent precision in terms of intra‐day repeatability was calculated (RSD% <3.4). Extraction recoveries from tomato products were calculated, by using a labelled internal standard (d4‐chlormequat), to be in the 93 ± 5–99 ± 7% range. The applicability of the method to the determination of chlormequat residues in tomato products was demonstrated. Copyright © 2002 John Wiley & Sons, Ltd.
Easy amino acid sequencing of sulfonated peptides using post‐source decay on a matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometer equipped with a variable voltage reflector
Authors: Hellman Ulf , Bhikhabhai Rama 
Published: October 2002

AbstractTryptic peptides were labeled with sulfonic acid groups at the N‐termini using an improved chemistry. The derivatization was performed in common aqueous buffers on peptides adsorbed onto a ZipTip™ C18, thus allowing simultaneous desalting/concentration of the sample. When only Arg‐terminating peptides were considered, the procedure from adsorption onto the ZipTip until analysis by MALDI‐PSD took about 10 min and several samples could be worked on in parallel. The resulting improved post‐source decay (PSD) fragmentation produced spectra containing only y‐ions. PSD amino acid sequencing of underivatized and derivatized synthetic peptides was compared. From the sequence information obtained from derivatized peptides isolated by ion selection from tryptic in‐gel digests, a protein was correctly identified which was difficult to analyze from an unclear peptide mass fingerprint analysis. The method was also applied to the identification and localization of phosphorylated Ser and Tyr residues in native and synthetic peptides. Copyright© 2002 John Wiley & Sons, Ltd.
Liquid chromatography/tandem mass spectrometric bioanalysis using normal‐phase columns with aqueous/organic mobile phases – a novel approach of eliminating evaporation and reconstitution steps in 96‐well SPE
Authors: Naidong Weng , Shou Wilson Z. , Addison Thomas , Maleki Saber , Jiang Xiangyu 
Published: October 2002

AbstractBioanalytical methods using automated 96‐well solid‐phase extraction (SPE) and liquid chromatography with electrospray tandem mass spectrometry (LC/MS/MS) are widely used in the pharmaceutical industry. SPE methods typically require manual steps of drying of the eluates and reconstituting of the analytes with a suitable injection solvent possessing elution strength weaker than the mobile phase. In this study, we demonstrated a novel approach of eliminating these two steps in 96‐well SPE by using normal‐phase LC/MS/MS methods with low aqueous/high organic mobile phases, which consisted of 70–95% organic solvent, 5–30% water, and small amount of volatile acid or buffer. While the commonly used SPE elution solvents (i.e. acetonitrile and methanol) have stronger elution strength than a mobile phase on reversed‐phase chromatography, they are weaker elution solvents than a mobile phase for normal‐phase LC/MS/MS and therefore can be injected directly. Analytical methods for a range of polar pharmaceutical compounds, namely, omeprazole, metoprolol, fexofenadine, pseudoephedrine as well as rifampin and its metabolite 25‐desacetyl‐rifampin, in biological fluids, were developed and optimized based on the foregoing principles. As a result of the time saving, a batch of 96 samples could be processed in one hour. These bioanalytical LC/MS/MS methods were validated according to “Guidance for Industry — Bioanalytical Method Validation” recommended by the Food and Drug Administration (FDA) of the United States.1 Copyright © 2002 John Wiley & Sons, Ltd.
Carbon isotope ratio analysis of organic moieties from fossil mummified wood: establishing optimum conditions for off‐line pyrolysis extraction using gas chromatography/mass spectrometry
Authors: Poole Imogen , van Bergen Pim F. 
Published: October 2002

AbstractMummified fossil wood was studied using off‐line pyrolysis‐gas chromatography/mass spectrometry to reveal detailed insights into the pyrolysis conditions that are needed to obtain simultaneously sufficient amounts of both cellulose and lignin markers for stable carbon isotope analyses. The off‐line pyrolysis was applied at a range of temperatures (200, 250 and 300 °C) and times (1 and 2 h) to determine the optimum temperature and time that yielded the highest quantity of true markers for lignin and cellulose. Increasing the time from 1 to 2 h had no effect whereas increasing the temperature led to large differences. The products released during the low‐temperature pyrolysis were mostly related to thermally labile moieties. Only at 300 °C were sufficient amounts of products released that represent true cellulose and lignin building blocks and which could be studied using gas chromatography/combustion isotope ratio mass spectrometry. Copyright © 2002 John Wiley & Sons, Ltd.
Generalization capabilities of co‐evolution in learning robot behavior
Authors: Berlanga A. , Sanchis A. , Isasi P. , Molina J.M. 
Published: October 2002

AbstractIn this article, a co‐evolutive method is used to evolve neural controllers for general

obstacle‐avoidance of a Braitenberg vehicle. During a first evolutionary process, Evolution Strategies

were applied to generate neural controllers; the generality of the obtained behaviors was quite poor.

During a second evolutionary process, a new co‐evolutive method, called Uniform Co‐evolution, is

introduced to co‐evolve both the controllers and the environment. A comparison of both methods shows that

the co‐evolutive approach improves the generality of controllers. © 2002 Wiley Periodicals, Inc.
A cross‐coupling controller using anH∞scheme and its application to a two‐axis direct‐drive robot
Authors: Fang Ren‐Wu , Chen Jian‐Shiang 
Published: October 2002

AbstractA cross‐coupling controller (CCC) using anH∞control scheme has been proposed to reduce the contouring error for a two‐axis, direct‐drive robot in tracking linear and circular contours effectively. Under the consideration that contour‐tracking performance is a primary target over point‐to‐point tracking performance in a trajectory‐tracking task, a CCC has been associated with joint controllers to reduce the contouring error by coordinating the motion of a two‐axis robot arm. Contouring performance can thus be improved significantly. Furthermore, the proposed CCC design, which is a typical Multi‐Input Multi‐Output (MIMO) system with linear time varying (LTV) characteristics, has been verified as being internally stable. A USM (ultrasonic motor)‐driven, two‐axis, direct‐drive robot is utilized to demonstrate the feasibility of the proposed scheme. Several experiments under various operating conditions are performed to validate its efficacy, and the results showed that the proposed scheme can reduce the contouring error significantly. © 2002 Wiley Periodicals, Inc.
Performance evaluation of decision making strategies for an embedded lane departure warning system
Authors: Kwon Woong , Lee Sukhan 
Published: October 2002

AbstractAn on‐board lane departure warning system embedded in a vehicle is composed of a localization module and a decision making module. The decision making module detects unintended lane departure so as to warn the driver of the danger. The performance of a decision making module is crucial to the performance of the total embedded system. This article proposes two heuristic decision making strategies: a lateral offset (LO) based strategy and a time‐to‐lane crossing (TLC) based strategy. The performance criteria of decision making strategies are proposed as: (1) false alarm rate, and (2) alarm triggering time (ATT). Numerical parameters of both strategies are optimized through numerical simulation, taking the performance criteria into consideration. The proposed strategies are incorporated into the prototype system and evaluated in real expressway experiments. The comparative study of both methods with experimental results shows the applicability of the on‐board lane departure warning system. © 2002 Wiley Periodicals, Inc.
Characterization of cell cultures with ToF‐SIMS and laser‐SNMS
Authors: Fartmann M. , Dambach S. , Kriegeskotte C. , Wiesmann H. P. , Wittig A. , Sauerwein W. , Lipinsky D. , Arlinghaus H. F. 
Published: October 2002

AbstractWe have applied time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) and non‐resonant laser secondary neutral mass spectrometry (NR‐laser‐SNMS) for examining freeze‐fractured, freeze‐dried primary osteoblast and cancer cells. Both techniques can simultaneously detect all masses with very high sensitivity and subcellular resolution. Because most of the sputtered particles are neutrals, laser‐SNMS has the additional advantage of being more quantitative. With both techniques, high‐resolution elemental and molecular images were obtained from cell cultures. Ion‐induced electron images were used to identify individual cells. Measurement of the Na/K ratio clearly demonstrated that the preparation techniques used are appropriate for preserving the chemical and structural integrity of living cells. Presputtering the samples with different primary ion dose densities makes it possible to take three‐dimensional images and to monitor the elemental distributions inside the cells. From the efficiency achieved, it can be concluded that ToF‐SIMS and laser‐SNMS are well suited for imaging trace element and molecule concentrations in biological samples. Copyright © 2002 John Wiley & Sons, Ltd.
Pd on Cu(110): growth mode monitored by LEIS
Authors: Delichère P. , Bertolini J. C. 
Published: October 2002

AbstractMetal on metal deposits can have very different, and interesting, physical and chemical properties compared with those of the pure metal. In this framework we investigated the behaviour of low amounts of palladium deposited at 300 K on the (110) face of copper, but copper is known to have a lower surface energy than palladium and therefore will tend to segregate at the surface, a process that depends on the temperature.The absolute calibration of the Pd deposit was made on a polycrystalline Cu sample with the combined use of XPS and Rutherford backscattering spectroscopy: for 6 × 1015 Pd atoms cm−2, the intensity ratio of Pd3d5/2/Cu3s is 7.2.For Pd deposited at room temperature on Cu(110), the presence of a large amount of copper at the surface is clearly evidenced by low‐energy ion scattering. The Pd atomic concentration at the surface does not exceed 15% for one monolayer (ML) of Pd deposited (1 ML = 1.1 × 1015 Pd atoms cm−2). This indicates either that Pd does not spray uniformly at the surface or that Cu diffusion and alloying effects do exist.These results are discussed in relation with some catalytic properties of the Pd on Cu(110) adlayers. Copyright © 2002 John Wiley & Sons, Ltd.
Transport of copper over paper in high‐voltage electrical insulation
Authors: Whitfield T. B. , Castle J. E. , Saracco C. , Ali M. 
Published: October 2002

AbstractCopper windings in the transformers used on national distribution networks are often insulated with layers of paper. In large current transformers the whole paper‐insulated assembly is immersed in an insulating mineral oil within a de‐aerated tank. Such transformers have a normal life span in excess of 30 years. However, from time to time, insulation problems arise and this is then associated with significant darkening of the paper. Analysis of the damaged paper by XPS shows that the darkening arises from the deposition, within the paper winding, of copper compounds, usually Cu2O or CuO.Laboratory studies in support of work designed to eliminate the problem have shown that copper diffusion occurs in mineral oil if it contains a trace of oxygen. In this paper we will show that the transport of copper through up to 20 layers of paper can be measured by XPS and that the concentration from one paper winding to the next declines in accord with Fick's law for non‐steady‐state diffusion.Measurements of surface concentrations by XPS have allowed determination of the diffusion coefficients and activation energy for the transport process and thus provide a basis for interpretation of the diffusion profiles found in the transformer in terms of time and temperature of operation. Copyright © 2002 John Wiley & Sons, Ltd.
Non‐destructive surface analysis applied to atmospheric corrosion of tin
Authors: Jouen S. , Hannoyer B. , Piana O. 
Published: October 2002

AbstractTin samples have been exposed in industrial, rural and urban outdoor atmospheres. Corroded surfaces were studied with Fourier transform infrared reflection absorption spectroscopy (FTIRAS), x‐ray diffraction (XRD), SEM, energy‐dispersive spectroscopy (EDS) analysis and Mössbauer spectroscopy. Corrosion is continuous and heterogeneous during the first 10 months of exposure, and the corrosion products seem mainly insoluble and non‐protective. Corrosion rate differs between each site of exposure, increasing from urban to rural area. Analyses performed reveal that the corrosion layers are mainly composed of poorly crystallized and hydrated stannic oxide SnO2·xH2O. Lower proportions of Sn(II) and Sn(IV) corrosion products are also identified as carbonates, sulphates and chlorides compounds. The FTIRAS and Mössbauer spectroscopy analyses remain the most adaptable to perform the characterization of tin corrosion products. They give reliable information about the chemical species, the valence state of tin nuclei and the evolution of the corrosion layer with time. Copyright © 2002 John Wiley & Sons, Ltd.
Is XPS combined with argon ion sputtering pertinent for depth profiling molybdenum‐implanted stainless‐steel layers?
Authors: Mottu N. , Vayer M. , Benoit R. , Erre R. 
Published: October 2002

AbstractThis paper discusses and compares depth profiles obtained on Mo‐implanted stainless steel by XPS and argon ion bombardment with those obtained by TRIM calculations and Rutherford backs scattering spectroscopy (RBS) analyses. The XPS profiles were highly dependent on the layer structure. When the structure remained highly crystallized, contamination carbon did not diffuse in the implanted layer and corrected Mo profiles were in agreement with RBS analyses. With a slight degradation of the implanted layer, corrected Mo profiles were still in agreement with RBS analyses but the carbon diffusion into the implanted layer was clearly visible (up to 10 at.%). When the implanted layer was completely amorphous, XPS profiles translated this amorphization and were highly dispersed. Copyright © 2002 John Wiley & Sons, Ltd.