bluuebunny/crossref_metadata_2025_split huggingface dataset:
Aluminum (III) interactions with the side chains of aromatic aminoacids
Authors: Mercero Jose M. , Matxain Jon M. , Lopez Xabier , Fowler Joseph E. , Ugalde Jesus M. 
Published: October 2002

AbstractAluminum (III) and magnesium (II) interactions with the aromatic containing aminoacid side chains are studied using the B3LYP approximate density functional. Bader and the natural bonding orbital (NBO) analyses have been performed on the optimized structures in order to shed light on the effect of the metal on the aromatic rings. We began by studying the interactions between the metal cations and benzene. Then a methyl was added to represent more accurately the phenylalanine functional group. We have also studied, in a similar way, the functional groups of the tyrosine and tryptophan aminoacids. The strongest bond is 447 kcal/mol, which occurs between the Al(III) and the indole. For magnesium, the strongest bond is 151 kcal/mol for the methyl–indole complex. As in the complexes of previous sections, the addition of the methyl leads to stronger binding complex, and this effect is significantly larger for aluminum than for magnesium. The NBO and Bader analyses revealed that the aromaticity of the carbon rings remains after interaction with magnesium. However, when the ring interacts with aluminum, aromaticity is lost, even though certain delocalization is kept. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Unified analytical treatment of one‐electron multicenter integrals of central and noncentral potentials over Slater orbitals
Authors: Guseinov I. I. 
Published: October 2002

AbstractUsing new complete orthonormal sets of exponential‐type orbitals introduced by the author (I. I. Guseinov, Int J Quantum Chem, submitted), the different analytical expressions are derived for the expansion of one‐ and two‐center electron charge density over Slater‐type orbitals (STOs) in terms of STOs about a new center. The expansion coefficients in these formulas are expressed through the overlap integrals with the same screening parameters. The one‐center expansion formulas in terms of STOs are also obtained for arbitrary central and noncentral potentials (CPs and NCPs). Using the expansion formulas obtained for the electron charge density and potentials, the general formulas are established for the multicenter molecular integrals of CPs and NCPs. In the formulas for the multicenter molecular integrals of CPs and NCPs, all the expansion coefficients and the overlap integrals are expressed through the binomial coefficients. The final results are especially useful for the calculation of these quantities for large quantum numbers. Using the derived expressions in terms of binomial coefficients, one‐electron molecular integrals over STOs can be evaluated efficiently and accurately from the series expansion formulas. The relationships obtained are valid for the arbitrary location, quantum numbers, and screening constants of atomic orbitals. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Interplay of intra‐ and intermolecular H‐bonds for the addition of a water molecule to the neutral and N‐protonated forms of noradrenaline
Authors: Alagona Giuliano , Ghio Caterina 
Published: October 2002

AbstractThe conformational flexibility of noradrenaline in its N‐protonated and neutral forms was considered at the Hartree–Fock (HF)/6‐31G* level, taking into account the orientation of the two hydroxy groups located on the catechol ring and the interconversion pathways between their stable arrangements. The difference in stability among the various forms of N‐protonated noradrenaline was maintained including either more diffuse functions on the heteroatoms or Møller–Plesset second order (MP2) correlation corrections. The embedding in aqueous solution, in the polarizable continuum model framework, of the conformers kept rigid at their in vacuo geometries favored the T conformers with respect to the G ones at the HF level (for neutral noradrenaline at the MP2 level as well). The addition of a single water molecule to noradrenaline (either N‐protonated or not) caused the intramolecular H‐bond within the side chain to weaken until formation of one or two intermolecular H‐bonds with water. This fact, coupled to the intramolecular H‐bond strain relaxation, further stabilized the G1 and T conformers. Continuum solvation of the hydrated clusters of neutral noradrenaline favored significantly the Twater adducts at the HF level, but only slightly at the MP2 level, because of their large energy gap in vacuo with respect to G1water, even enhanced by MP2 geometry optimizations. The dependence of the potential energy profile for the NH2 group rotation on the catechol ring and side chain OH group orientation was examined in noradrenaline and compared to the trend shown by dopamine. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Comparison of two‐electron densities reconstructed from one‐electron density matrices
Authors: Herbert John M. , Harriman John E. 
Published: October 2002

AbstractWe consider approximate reconstruction of spinless and spin‐resolved two‐electron charge densities, intracule densities, and extracule densities utilizing only the one‐electron reduced density matrix. Using large basis set, configuration interaction density matrices for the ground state of Be, we compare the two‐electron densities obtained using several proposed reconstruction functionals (“natural orbital functionals”) for the two‐electron density and density matrix. We also analyze the intracule and extracule densities obtained from these reconstructions. Several of the proposed natural orbital functionals are found to produce unphysical negative values for the pair density when two parallel‐spin electrons approach one another. Ancillary results from this study include new, simplified formulas for the intracule and extracule densities, and a mathematical justification for an approximate relation between atomic intracule and extracule densities that has previously been reported on the basis of extensive Hartree–Fock calculations. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Local kinetic energy and local temperature in the density‐functional theory of electronic structure
Authors: Ayers Paul W. , Parr Robert G. , Nagy Agnes 
Published: October 2002

AbstractVarious thermodynamic elements of the density functional theory of electronic structure are reviewed and clarified. Detailed argumentation is given for the particular “del dot del” definition of the local kinetic energy density and local temperature. The temperature measures the “nighness” of an electron pair, thus playing a key role in quantitative (exchange and kinetic energy functionals) and qualitative (electron localization functions) tools based on the electron pair density. Two different derivations are given of the Gaussian model for the phase‐space distribution function, from which one obtains an approximation to the entropy of the charge distribution. The full thermodynamic description is briefly discussed. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Trends in hyperfine coupling constants and electron‐spin g factors for X\documentclass{article}\pagestyle{empty}\begin{document}$^{2}\Sigma^{+}_{(g,u)}$\end{document} diatomics with 1,3, and 5 valence  electrons
Authors: Bruna Pablo J. , Grein Friedrich 
Published: October 2002

AbstractA comparison of electron spin resonance (ESR) parameters calculated for X2Σ(g,u)+ diatomic radicals is presented, including Li2+, LiK+ with one valence electron (VE); Li2−, LiK−, LiBe, LiCa, LiB+, LiGa+, Be2+, and BeCa+ with 3 VEs; and B2+, BGa+ with 5 VEs. The Aiso and Adip constants are studied using 6‐311+G(2df) basis sets and several methods (UHF, CISD, MP2, B3LYP, PW91PW91). For the s‐rich radicals with 1 and 3 VEs, it is found that Aiso≫Adip≈0, whereas for those of pσ‐type (such as LiB+/LiGa+ with 3 VEs, and all present 5 VE radicals), the values of Aiso and Adip are generally similar. The electron‐spin g factors are calculated using perturbation expansions up to second order, a Hamiltonian based on Breit–Pauli theory, and correlated (MRCI) wave functions. All radicals have negative values of Δg∥ and Δg⊥. The sum‐over‐states expansions for Δg⊥ are dominated by the coupling with just one or two 2Π excited states. The Δg⊥'s of the first‐row radicals Li2+, Li2−, Be2+, LiBe, LiB+, and B2+ are about −60, −5, −120, −215, −3290, and −1300 ppm, respectively, while for the mixed first/third‐row counterparts LiK+, LiK−, BeCa+, LiCa, LiGa+, and BGa+ they are about −1200, −2480, −1000, −7840, −93700, and −800 ppm, respectively. These results show the strong influence heavier atoms with larger spin‐orbit constants have on g⊥ shifts. The smaller Δg⊥ of BGa+ (when compared with B2+) is caused by the 3σ→1π and 3σ→2π excited states contributing positively and negatively, respectively, to this shift. Such positive contribution is at variance with the rule stating that an excitation of type σ→π (SOMO→virtual MO) should contribute negatively. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Cumulant‐based approximations to reduced density matrices
Authors: Harris Frank E. 
Published: October 2002

AbstractThe use of cumulant expansions for the approximation of reduced density matrices (RDMs) is reviewed. It is pointed out that the oft‐cited theorems of Nakatsuji and Rosina are insufficient to guarantee either N‐representability or that an N‐representable RDM has a unique antecedent wave function. Approximations involved in Mazziotti's recently proposed “formal solution for reconstruction” are identified. The behavior of his scheme, and of an older one in which all cumulants beyond the second are neglected, are illustrated by detailed examination of a model problem. The limited experience provided by this example casts doubt as to the probable effectiveness of Mazziotti's reconstruction scheme. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Nuclear electromagnetic shieldings via charge and current density functions
Authors: Lazzeretti Paolo 
Published: October 2002

AbstractThe general concept of time‐dependent charge and current densities for the electrons in a molecule responding to electromagnetic fields is considered. It is shown that nuclear electric and electromagnetic shieldings, related to absorption intensity in infrared and vibrational circular dichroism spectroscopies, can be expressed in terms of density functions in real space. Plots of charge and current densities obtained by the theoretical methods developed in the present study are expected to provide a physical basis on the absorption process and simple tools for the interpretation of vibrational spectroscopy parameters. © 2002 John Wiley & Sons, Inc. Int J Quantum Chem, 2002
Electron ionization mass spectral fragmentation of deoxynivalenol and related tricothecenes
Authors: Rodrigues‐Fo Edson , Mirocha C. J. , Xie Weiping , Krick Thomas P. , Martinelli J. A. 
Published: October 2002

AbstractCareful analysis of the electron impact (EI) mass spectral data obtained for the trimethylsilyl (TMS) ethers of known trichothecene mycotoxins of the deoxynivalenol group permitted the construction of a database useful for the identification of these mycotoxins directly from a gas chromatography/mass spectrometry (GC/MS) run. Structures of the ions at m/z 103, 117, 147 and 191 were elucidated by high‐resolution mass spectrometry (HRMS) and a fragmentation scheme was suggested. The relative abundances of these ions in the mass spectra of the trichothecenes allowed a fast structural diagnosis during analysis of biological matrices. A new mycotoxin of this group, 3‐acetylnivalenol, was tentatively identified by using MS data interpretation only. Copyright © 2002 John Wiley & Sons, Ltd.
XPS characterization of biocompatible hydroxyapatite–polymer coatings
Authors: Casaletto M. P. , Kaciulis S. , Mattogno G. , Mezzi A. , Ambrosio L. , Branda F. 
Published: October 2002

AbstractHydroxyapatite coatings on polymeric substrates have been prepared by treating samples of poly(methyl methacrylate) (PMMA) and poly(2‐hydroxyethyl methacrylate) with a biomimetic method and by producing a mechanical mixture of polymers (PMMA and poly(butylmethyl methacrylate) and hydroxyapatite (1 : 1). The surface chemical composition of the samples has been studied by using X‐ray photoelectron spectroscopy. Both the reference polymers and the hydroxyapatite coatings have been analyzed. The surface modifications induced by interaction of the coatings with osteoblast cells have been studied as a function of the exposure time, after in vitro treatment for 7, 15 and 21 days. Quantitative XPS analysis enabled us to compare the quality of the samples and the different response to the in vitro treatment. Copyright © 2002 John Wiley & Sons, Ltd.
Characterization of thin Co/ZrO2 catalytic films by XPS, SEM and SAM
Authors: Stefanov P. , Atanasova G. , Robinson K. , Julbe A. , Guizard C. , O'Hara P. , Marinova Ts. 
Published: October 2002

AbstractThin Co/ZrO2 and Co/S‐ZrO2 catalytic films for hydrocarbon‐selective catalytic reduction (HC‐SCR) of NOx were prepared and characterized by means of XPS, SEM and scanning Auger microscopy (SAM). Zirconia was deposited on a fibrous inconel support (Bekaert) by the sol–gel method. Cobalt was deposited on pure and pre‐sulphated zirconia films by impregnation with a 6% CoCl2 solution. The photoelectron spectra indicated that cobalt was present mainly in the Co2+ state in the form of CoO‐like species. The SEM/SAM results showed homogeneous distribution and a smaller size of the Co particles deposited on pre‐sulphated zirconia compared with cobalt deposited on pure zirconia. The results indicated that sulphating of zirconia improved the dispersion of cobalt on the surface, which is a prerequisite for a good SCR performance. Copyright © 2002 John Wiley & Sons, Ltd.
Combined TPD and FTIR studies of Co/ZrO2 catalysts: determination of the cobalt dispersion
Authors: Hadjiivanov K. , Panayotov D. , Avreyska V. , Tsyntsarski B. , Klissurski D. , Marinova Ts. 
Published: October 2002

AbstractAdsorption of NO on cobalt catalysts supported on zirconia and sulphated zirconia results in the formation of three main types of species: Zr4+(SO42−)‐NO and Zr4+(NO3−)‐NO nitrosyls (infrared band at 1940‐1906 cm−1), which are of low stability (temperature‐programmed desorption maximum at 55–80°C); Co2+(NO)2 geminal nitrosyls (set of bands at 1903‐1868 and 1814‐1777 cm−1) characterized by temperature‐programmed desorption maxima at 90–100°C; and linear Con+‐NO species (1942‐1858 cm−1) desorbing at 120–140°C. On the basis of the results obtained, a simple temperature‐programmed desorption technique for determination of the cobalt dispersion is developed. Copyright © 2002 John Wiley & Sons, Ltd.
Infrared investigation of the transformation of NO over supported Pt‐ and Rh‐based three‐way catalysts
Authors: Granger P. , Praliaud H. , Billy J. , Leclercq L. , Leclercq G. 
Published: October 2002

AbstractThe adsorption of NO and its reaction with CO have been investigated on Pt/Al2O3 and Rh/Al2O3 by in situ infrared spectroscopy. Different spectroscopic features have been observed on Rh and Pt after NO exposure at various temperatures, mainly related to the build up of positively, neutral and negatively charged NO species on Rh, with neutral NO species predominating on Pt. The formation of Rh‐NO+ and gem‐dicarbonyl species RhI(CO)2 during the adsorption of NO and the CO + NO reaction has been associated mainly with surface Rh oxidation at low temperature. On the other hand, the reductive properties of CO prevail above 250°C leading to the disappearance of the gem‐dicarbonyl structure. These infrared observations have been discussed on the basis of previous kinetic observations. Copyright © 2002 John Wiley & Sons, Ltd.
Angle‐resolved XPS analysis of molybdenum and tungsten in passive films on stainless steel PVD alloys
Authors: Olsson C.‐O. A. , Mathieu H.‐J. , Landolt D. 
Published: October 2002

AbstractPassive films on physical vapour deposited alloys, based on 304L with additions of 20 at.% of molybdenum and tungsten, were studied with angle‐resolved XPS. The samples were anodically polarized in a sulphate solution to potentials in the low and high passive region, respectively. In the low passive region, the Mo spectrum contained a strong contribution of Mo(IV) hydroxide. In the high passive region, higher fractions of hexavalent species were found; W(VI) gave a stronger contribution than Mo(VI), as can be understood by the lower solubility of the W(VI) salts. Contributions to tetravalent molybdenum were found to consist of oxide (MoO2) as well as oxyhydroxide compounds. For tungsten, the dominating tetravalent contribution was WO2. Copyright © 2002 John Wiley & Sons, Ltd.
Oxidation of stainless steel under dry and aqueous conditions: oxidation behaviour and composition
Authors: Wambach J. , Wokaun A. , Hiltpold A. 
Published: October 2002

AbstractThe oxidation of austenitic stainless steel (316Ti) under dry oxidation and under pressurized aqueous conditions, both at ∼300°C, was studied by applying XPS, depth profiling and x‐ray diffraction. After dry oxidation a relatively smooth surface was found, depleted of chromium, nickel and molybdenum and leaving behind nearly exclusively iron oxides. In the oxide layer chromium oxides were detected, followed by metallic nickel and molybdenum. The growth of the whole oxide layer follows a logarithmic growth law. Under aqueous conditions a rougher surface was found, with oxide layers being a factor of ≥10 thicker than under dry oxidation conditions. A greater variety of the oxides were found, e.g. chromium and nickel oxides and hydroxides are present in considerable amounts already at the sample surfaces. Again, molybdenum is first detected in the oxide layer. During the first 60 days of steel oxidation in pressurized water, the oxide layer formation follows a parabolic growth law. Copyright © 2002 John Wiley & Sons, Ltd.
Corrosion inhibition of Al 6061 T6/Al2O3p 10% (v/v) composite in 3.5% NaCl solution with addition of cerium (III) chloride
Authors: Traverso P. , Spiniello R. , Monaco L. 
Published: October 2002

AbstractThe effect of cerium on corrosion inhibition of Al 6061 T6/Al2O3p 10% (v/v) metal matrix composite in aerated 3.5% NaCl solution after different immersion times at room temperature and pressure was investigated.Experimental tests were conducted at different inhibitor agent concentrations (0, 200, 1000 and 2000 ppm of cerium) and for exposure times ranging from 2 h to 30 days. Corrosion inhibition power evaluation and surface layer characterization have been carried out by electrochemical (polarization potentiodynamic curves and impedance measurements) and free corrosion tests followed by several instrumental analyses (optical microscopy, x‐ray photoelectron spectroscopy, scanning electron microscopy).Electrochemical data have shown that cerium compounds offer a noticeable inhibition level against localized corrosion in all considered cases and that the maximum protective power against corrosion attack is evident when the inhibitor is added at a 200 ppm concentration. Surface analysis revealed chemical and morphological characteristics of the passive layer. In particular, a higher amount of inhibitor led to the formation of a surface film with a higher content of cerium but without homogeneous distribution. This behaviour decreased the protection power of the passive layer while increasing composite substrate corrosion tendency. Copyright © 2002 John Wiley & Sons, Ltd.
Use of ToF‐SIMS in the study of corrosion processes: Monel 400 steam generator tubing under CANDU start‐up conditions
Authors: Francis J. T. , Brennenstühl A. M. , Ramamurthy S. , McIntyre N. S. 
Published: October 2002

AbstractThis work explores the use of time‐of‐flight secondary ion mass spectrometry to characterize films on Monel 400 steam generator tubing that has been subjected to simulated CANDU reactor start‐up conditions. The results are compared with those obtained using more traditional techniques, including scanning Auger microscopy and x‐ray photoelectron spectroscopy. Copyright © 2002 John Wiley & Sons, Ltd.
Quantitative analysis of the plasmon loss intensities in x‐ray photoelectron spectra of magnesium
Authors: Kurth M. , Graat P. C. J. 
Published: October 2002

AbstractX‐ray photoelectron spectra of free‐electron metals such as magnesium and aluminium contain pronounced electron energy‐loss peaks due to plasmon excitations. Part of the intensity contained in these plasmon peaks is of an intrinsic nature. In this work a procedure is presented that allows the determination of intrinsic and extrinsic contributions to the plasmon loss structure and accounts for possibly different electronic properties at the surface. It is based on the reconstruction of a spectrum by convolution of physically realistic functions for the x‐ray energy distribution, the core‐level main peak, the cross‐sections for plasmon excitation and instrumental broadening. The procedure has been applied to an Mg 2p spectrum, giving a total intrinsic plasmon contribution of 46% relative to the main peak intensity. Copyright © 2002 John Wiley & Sons, Ltd.
Quantitative analysis of low‐energy N2+ implantation in TiC using XPS and TRIM
Authors: Fuentes G. G. , Elizalde E. , Sanz J. M. 
Published: October 2002

AbstractWe have studied the implantation of 2 keV N2+ ions in TiC. Both the shape and binding energy of the different core levels, as well as their modification, have been analysed during the implantation process. In order to quantify the implantation steps as a function of the N2+ dose, we have used a Monte‐Carlo‐based TRIM code to simulate the implantation profile of the nitrogen ions, except for the absolute atomic concentration, which is then determined by making use of the usual equations for quantitative XPS.We have derived the atomic concentration of implanted nitrogen atoms, i.e. N(z, DN), as a function of depth and the N2+ ion dose in terms of TRIM simulated in depth profiles and the usual equations for quantitative XPS analysis. Owing to the accumulation effect and the sputtering of the target surface, the static nitrogen profiles NN(z) derived by TRIM evolve to an erf(z) distribution with increasing ion dose DN. A proper analysis of the Ti 2p, C 1s and N 1s peaks also allows different species to be distinguished and their distribution in depth. Copyright © 2002 John Wiley & Sons, Ltd.
Factors determining preferential sputtering in InGaAs system: angle‐resolved small‐area XPS investigation
Authors: Padeletti G. , Ingo G. M. 
Published: October 2002

AbstractDifferent Ar+ energies (2 and 5 keV) were used to sputter (100) Ga0.73In0.27 As material at room temperature and under liquid nitrogen cooling. The preferential sputtering phenomena related to the different ion energies used have been investigated. Using angle‐resolved small‐area x‐ray photoelectron spectroscopy (AR‐SA‐XPS), chemical composition variations of the sputtered surface have been put in evidence. The results show an indium depletion on the outermost Ga0.73In0.27 As layer operating at room temperature. Indeed, even though indium and arsenic depletion is observed under liquid nitrogen cooling, the AR‐SA‐XPS results show that the effect is lower with respect to the surfaces sputtered at room temperature. These results are discussed in the framework of models proposed for explaining preferential sputtering phenomena. Copyright © 2002 John Wiley & Sons, Ltd.