bluuebunny/crossref_metadata_2025 huggingface dataset:
DFT calculations and parameterization of the approximate valence bond method to describe the phosphoryl transfer reaction in a model system
Authors: Ginalski Krzysztof , Grochowski Pawel , Lesyng Bogdan , Shugar David
Published: October 2002

Density functional theory (DFT) calculations have been performed at the B3LYP/6‐31G+(d,p) level for a model phosphodiester system to describe a transphosphorylation reaction that mimics the phosphoryl transfer process in serine/threonine protein kinases. The DFT energy and electrostatic potential data have been used to extend the parameterization of the approximate valence bond (AVB) method. AVB mimics well the DFT results and is planned for use as a fast potential energy generator to simulate phosphoryl transfer processes in protein kinases using the quantum classic molecular dynamics approach. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Dipole moments calculations of transition metal mononitrides: ScN, TiN, VN, and CrN: Limits of the CCSD(T) method
Authors: Jansík Branislav , Kellö Vladimír , Urban Miroslav
Published: October 2002

Coupled‐cluster calculations of selected molecular properties of ScN, TiN, VN, and CrN in their ground states are presented. It is shown that the single determinant reference Restricted Open Shell Hartree‐Fock Coupled Clusters Singles Doubles noniterative Triples (ROHF‐CCSD(T)) method provides reasonably accurate bond distances, harmonic frequencies, and most dipole moments of these molecules but fails to predict sufficiently accurate dipole moment of CrN. The reason for the low accuracy in obtaining the dipole moment of CrN is analyzed and is attributed to the presence of the series of large single excitation CC amplitudes. This affects the correct response of the molecular CC wavefunction to the external field. Quasirelativistic effects are considered using the Mass‐velocity‐Darwin correction. Changes of dipole moments due to relativity are stressed, and trends throughout the series of molecules are analyzed using their bonding characteristics. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Hopping conductivity in nucleotide base stacks*
Authors: Ladik J. , Ye Y.‐J.
Published: October 2002

The frequency‐dependent complex hopping conductivities of single nucleotide base stacks and base pair stacks were calculated on the following basis: (1) The determination of the density of states of these disordered systems with the help of the matrix block negative counting method. (2) Using the inverse iteration technique, the Anderson localization of the one‐electron functions belonging to the physically interesting levels were computed. (3) With the help of the latter quantities the hopping frequencies corresponding to the relative motion of the base pairs with respect to each other (acoustic phonons) were determined. (4) Finally, using a random‐walk theory the frequency‐dependent complex conductivities [σ(ω)] were computed. The |σ(ω)|−ω curves show a saturation at ω≈1010 s−1. The |σ(ω)|'s have the values in the base pairs case (taking into account the role of the sugar–phosphate backbone, basis set, and correlation effects) are a few times 1 Ω−1 cm−1 for ω>1010 s−1. This room temperature result is in excellent agreement with the energy loss (in a resonant cavity) experiment on lambda phage deoxyribonucleic acid (DNA) of Gruner and co‐workers. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Models for low‐temperature helium dimers and trimers
Authors: Lohr Lawrence L. , Blinder S. M.
Published: October 2002

We have shown that a simple model based on pairwise deltafunction potentials can, with an appropriate choice of parameters, represent the general behavior of ultra‐low temperature helium dimers and trimers, including all possible isotopomers. The species 4He2, 4He3, and 4He23He are stable, with binding energies of approximately 1.3, 100, and 10 mK, respectively. An Efimov state for 4He23He is also predicted, bound by 2.4 mK. The remaining dimers and trimers, 4He 3He, 3He2, 4He 3He2, and 3He3, are evidently unstable. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Theoretical modeling of infrared spectra of salicylaldehyde and its deuterated derivatives*
Authors: Boczar Marek , Wójcik Marek J. , Szczeponek Krzysztof , Jamróz Dorota , Ikeda Susumu
Published: October 2002

Theoretical simulation of the νs stretching band is presented for salicyladehyde and its deuterated derivatives taking into account an adiabatic coupling between the high‐frequency O–H(D) stretching and the low‐frequency intramolecular OO stretching modes, linear and quadratic distortions of the potential energy for the low‐frequency vibration in the excited state of the O–H(D) stretching vibration, and resonance interaction between the O–H and the C–H stretching vibrations in the aldehyde group. The experimental infrared and Raman spectra of the liquid salicylaldehyde have been recorded. The geometry and experimental frequencies are compared with the results of our HF/6‐31++G**, MP2/6‐31++G**, and Becke3LYP/6‐31++G** calculations. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
SU(3)×𝒮20 algebras for uniform spin‐1 ensembles on [2H12C]20, or [14N]20, dodecahedrane‐type lattices and analogous isotopomeric [M2012C40] met‐carb subensembles: M‐based cardinalities and completeness of 𝒮20 spin irreps, via hierarchical {𝒞λ⊢(n=20):(M)} designs of polyhedral combinatorics*
Authors: Temme F. P.
Published: October 2002

The M‐based hierarchy cardinalities of spin irreps for \documentclass{article}\pagestyle{empty}\begin{document}$[A]_{20}^{(I_{i}=1)}$\end{document} uniform nuclear magnetic resonance (NMR) /isotopomer spin ensembles are derived. Such ideas define the completeness of the number‐partition‐based (intermediate) combinatorial designs (on M) themselves inherent in specific λ⊢n digit assembly combinatorial properties. Illustrative M‐subspatial irrep subsets are derived via Schur decompositions from symbolic algorithms (Sagan, B. E. Symmetric Group: Representations, C‐Algorithms, Symmetric Functions; Wadsworth: Belmont, CA, 1991; SYMMETRICA package, as per Kerber, A.; Kohnert, A.; Lascoux, A. Symbolic Comput 1992, 14, 195). The results are discussed in the context of the independant cardinality of underlying system scalar invariants (SI) corresponding to the democratic auxiliary labels (Chem Phys 1998, 238, 245; J Math Chem in press), or projective recoupling, of 20‐fold dual tensorial sets. Landau‐like 𝒮n‐maps for fundamental terms plus statistical weighted subsidary maps yield the independent ∣SI∣s (see Europhys Lett in press). Geometric aspects of the dual group mappings imply that eventually large cage NMR ensembles must be governed by a local, rather than a global, symmetry, with the former related to established spectral deceptive NMR. This suggests a further role for dynamical networks in NMR, beyond that given by K. Balasubramanian (J Chem Phys 1983, 78, 6369) as implied by D. Watts (Small Worlds; Princeton Univ. Press: Princeton, NJ, 1999). © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Brueckner orbitals and density‐functional theory
Authors: Lindgren Ingvar , Salomonson Sten
Published: October 2002

By means of many‐body perturbation theory (MBPT) it is shown that minimizing the energy expectation value of a closed‐shell system in a certain order of the perturbation expansion by varying the partitioning of the Hamiltonian leads to a zeroth‐order function, which—as the order of perturbation increases and provided the expansion converges properly—approaches a determinant of Brueckner orbitals. It is also shown that the energy eigenvalues of the Brueckner orbitals represent the corresponding ionization energies of the system, including orbital‐relaxation and correlation effects to all orders of perturbation theory. This is a generalization of the Koopmans theorem in Hartree–Fock theory. The MBPT treatment is used for a discussion of the density‐functional theory, and a new model is proposed—referred to as the Brueckner–Kohn–Sham scheme—where also the electron correlation is included in the functional. This leads to a nonlocal exchange‐correlation potential, quite similar to that of Brueckner orbitals (BO), implying that the orbitals of the new scheme are essentially BO. Arguments are given that also the orbitals of other schemes with a purely local potential, such as the standard Kohn–Sham (KS) scheme, would be close to BO. This has been conjectured by Heßelmann and Jansen ( J Chem Phys 2000, 112, 6949), and the present work gives more direct evidence of that. This might explain the recent observations that the KS orbitals and energy eigenvalues do have more physical significance than was originally anticipated. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Coupled‐perturbed Hartree–Fock treatment of infinite periodic systems: Application to static polarizabilities and hyperpolarizabilities of polydiacetylene, polybutatriene, and interacting pairs of polyacetylene chains
Authors: Kirtman Bernard , Champagne Benoît , Gu Feng Long , Bishop David M.
Published: October 2002

Static longitudinal polarizabilities (α) and second hyperpolarizabilities (γ) are determined for three quasi‐one‐dimensional polymeric systems using a new crystal orbital coupled‐perturbed Hartree–Fock method. Calculations of α and γ for polydiacetylene and polybutatriene at two different geometries are analyzed in terms of the alternation of bond lengths along the carbon backbone. For the third polymer, polyacetylene, the treatment is applied to a pair of chains in the two different configurations that occur in a stretched fiber. The results are in marked contrast to those previously obtained for short and medium‐sized oligomers. In order to relate the pair interaction effect between infinite chains to the bulk susceptibility of the natural fiber additional finite oligomer calculations are carried out. This allows us to discuss the role of finite chain length distribution, many‐body interchain interactions, and electron correlation. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Data mining, ab initio, and molecular mechanics study on conformation of phenylalanine and its interaction with neighboring backbone amide groups in proteins
Authors: Duan Guilin , Smith Vedene H. , Weaver Donald F.
Published: October 2002

Data mining results for 1029 X‐ray protein structures demonstrate that there are, on average, more than nine phenylalanine residues in a typical protein structure. Moreover, the conformations of these phenylalanine residues are not arbitrary but fall into four regular types. These four phenylalanine conformational types can be related to the interaction between the phenylalanine's phenyl group and its neighboring backbone amide groups. They are designated as “Aphe,” “Cphe,” “ACphe,” and “NACphe,” respectively, depending on the presence and absence of such phenyl–amide interactions. It is shown that 96.2% of the phenylalanine residues occurring in proteins fall into the first three types, which involve one or two types of these interactions. The side chain and associated backbone fragment of each phenylalanine type have characteristic conformational regularities. The interaction potential energy surfaces of these interactions were exhaustively and systematically evaluated by means of the validated CHARMm force field. We show that this force field produces interaction energies comparable to BSSE‐corrected values calculated using MP2/6‐311G(2d,2p) and MP2/6‐31+G(2d,p). The phenyl–amide interactions occurring in proteins have configurations corresponding to a stabilization energy of up to 11 kJ/mol in vacuum. None occur that would correspond to a phenyl–amide repulsion. We conclude that the phenyl–amide interaction is one of the factors responsible for the conformational regularity of the phenyalanine in proteins and that it is of significance due to its strength and common occurrence. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
The Löwdin challenge: Origin of the n+ℓ, n (Madelung) rule for filling the orbital configurations of the periodic table
Authors: Allen Leland C. , Knight Eugene T.
Published: October 2002

The periodic table may be viewed as an s‐block and p‐block framework internally perturbed by d and f electrons. A perturbation operator is devised to search the table for small energy changes and to locate the d‐ and f‐blocks. The unusually large s/d and s/f radial extent ratios are discussed and related to the unexpected order of ns and (n−1)d occupancy and to the charge transfer from s to d orbitals that occurs in transition metal complexes. The orbitals and their properties, obtained from Desclaux's 1973 Fock–Dirac neutral atom calculations for Z=1–118, are employed to verify our analysis. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Redox chemistry of organoselenium compounds: Ab initio and density functional theory calculations on model systems for transition states and intermediates of the redox cycle of selenoenzymes
Authors: Benkova Zuzana , Kóňa Juraj , Gann Gudrun , Fabian Walter M. F.
Published: October 2002

Ab initio [Hartree–Fock (HF)] and density functional theory (B3LYP) ECP calculations on intermediates and transition states of the reduction of phenylseleninic acid with hydrogen sulfide and of seleninic acid with benzenethiol as models for the species involved in the redox cycle of selenoenzymes are presented. Selenenyl sulfide is found to be the final product of the reduction reaction with sulfides. Further reduction to the selenol requires surmounting a substantial barrier (∼50 kcal mol−1). The final step of the redox cycle—oxidation of the selenol by hydrogen peroxide—is strongly exothermic. In case of the unsubstituted derivative H2Se three mechanisms for this oxidation are found [concerted and stepwise 1,2‐hydrogen and oxygen shift (TS6A, TS6B, resp.) and a four‐membered transition state TS6C]. For the oxidation of phenylselenol only TS6A and TS6B are obtained. For nearly all calculated structures the HF wave functions show a triplet instability. In contrast, at the B3LYP level only TS6C has a significant triplet instability. On the basis of QCISD(T)//QCISD results a mechanism involving TS6C seems highly unlikely. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Relativistic dynamics of positronium atom in uniform magnetic field*
Authors: Datta Sambhu N. , Misra Anirban
Published: October 2002

The relativistic dynamics of the positronium atom in a uniform external magnetic field is investigated in this work. Following our previous work on a general system of two spin‐½ particles, here too we choose three distinct forms of interaction, viz., the Bethe–Salpeter interaction, the Breit interaction, and the projected Breit interaction. We also include the interaction of the anomalous magnetic moment with the external magnetic field. As the system is overall electrically neutral, the center‐of‐mass motion can be completely separated out. The residual Hamiltonian operator describes only the relative movement. This operator can be brought into a form where the one‐particle part is exactly separable into positive and negative energy states and is diagonal. However, as a marked departure from our previous methodology, the separation of the odd terms from the transformed interaction operator up to order α2, where α is the fine‐structure constant, is accomplished here by a somewhat different procedure so as to avoid those unitary transformation operators which contain the mass difference (m1−m2) in the denominators of their arguments. Because of the nature of the one‐particle operators, the odd terms of order α2 are completely removed in the present treatment. Also, no unphysical term of order α2 results from the use of the Breit interaction. The effect of the virtual electron–positron pair, which appears at second order in the fine‐structure constant, is also incorporated in the Hamiltonian. Again, the reduction of the order‐α2 pair term to a previously known simpler form is exactly achieved here. Thus we obtain three different versions of the relativistic Hamiltonian operator for a positronium atom in a uniform magnetic field, with the electrodynamical interactions taken into account through order α2. All three lead to the same energy for the same spinor wave function under the so‐called uU separation. These operators are now used to calculate the conventional nonrelativistic limit, and the same limiting operator is obtained in every case. For zero magnetic field, the Hamiltonian reduced to the nonrelativistic limit is found to be identical with the standard nonrelativistic Hamiltonian known for the positronium atom. We also obtain the nonrelativistic limit Hamiltonian for the positronum atom in the high‐field case, where the ratio of the applied magnetic field and the velocity of light B/c, or, more precisely, the Larmor frequency ωL=eB/2mc, is of the order of one atomic unit. Finally, in the Appendices, we discuss the nature of the eigenfunctions and indicate how one can calculate these functions correctly through the zeroth order in the fine‐structure constants and find the eigenvalues correct through the second order. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Analytical and ab initio studies of effective exchange interactions, polyradical character, unpaired electron density, and information entropy in radical clusters (R)N: Allyl radical cluster (N=2–10) and hydrogen radical cluster (N=50)
Authors: Yamaguchi Kizashi , Kawakami Takashi , Takano Yu , Kitagawa Yasutaka , Yamashita Yoshifumi , Fujita Harunori
Published: October 2002

Analytical expressions of total energies, effective exchange integrals, polyradical character, spin density, unpaired electron density, and information entropy are derived for allyl radical dimers and trimers on the basis of the Hubbard model in order to elucidate interrelationships among several broken‐symmetry and symmetry‐adapted approaches to molecular magnetism. Ab initio unrestricted Hartree–Fock and hybrid density functional theory (DFT) calculations of allyl radical dimers to decamers are also carried out for confirmation of characteristics revealed by the analytical investigations. A mesoscopic hydrogen radical cluster with 50 radical sites is studied by the ab initio hybrid DFT methods to elucidate functional behaviors of the above quantities with change of interatomic distance. The potential curves for the lowest and highest spin states of the cluster by these methods are depicted for the purpose. Implications of the present computational results are discussed in relation to size‐consistent spin projection and size effects on effective exchange interactions in mesoscopic radical clusters. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Bounds on electrostatic interactions
Authors: Whitten J. L.
Published: October 2002

This article deals with two topics: bounds on electrostatic interactions and new approaches to the expansion of electron densities in ab initio calculations on large systems. Schwartz inequalities derived from positive definite self‐energy integrals are reviewed and new bounds on electrostatic interactions consisting only of kinetic energy and overlap integrals are derived. Several applications are discussed. In the expansion of electron densities occurring in the treatment of large systems, numerous densities that are relatively small in magnitude are expanded whenever possible in terms of large densities already present in the calculation. Rigorous error bounds are used to judge the acceptability of the expansion. Proceeding in this way allows a simplifying reorganization of the information that must be stored for use in many‐electron configuration interaction calculations, thereby enabling the application of this method to larger systems. © 2002 John Wiley & Sons, Inc. Int J Quantum Chem, 2002
Important correlation effects for the Er3+ 4f114S3/2→4I15/2 laser transition energy
Authors: Beck Donald R.
Published: October 2002

Most of the important correlation effects transitions within the 4fn manifold of rare‐earth atomic ions are identified as coming from three sources: 4f2 pair correlations, single excitations from the valence shell and shallow core, and pair excitations where both of the electrons go into the incomplete 4f subshell (exclusion effects). A method (REDUCE) of managing the large basis sets encountered is discussed. Relativistic configuration interaction calculations are done to obtain the energy of the laser transition (in, e.g., GaN) Er3+ 4I15/2→4S3/2, to which correlation contributes ∼4000 cm−1. The residual error of 864 cm−1 may be due to missing second‐order effects and to truncation of the angular basis. © 2002 John Wiley & Sons, Inc. Int J Quantum Chem, 2002
Bond orders in heteroaromatic rings*
Authors: Doerksen Robert J. , Thakkar Ajit J.
Published: October 2002

Bond orders are calculated at the Hartree–Fock and second‐order, Møller–Plesset (MP2) level for 324 distinct ring bonds in 60 heterocyclic molecules. These include benzene and 12 azines, pyrrole and 9 azoles, furan and 9 oxazoles, thiophene and 8 thiazoles, boroxine, trioxadiborole, borazine and 9 azaborinines, 3 azaboroles, and 3 oxazaboroles. The correlated bond orders are generally, but not always, smaller than their Hartree–Fock counterparts. Gordy bond orders differ from the ab initio ones by large amounts. A plot of MP2 bond orders versus bond lengths shows clearly that an empirical Gordy‐type relationship cannot be very accurate. Some trends in bond orders are identified. © 2002 John Wiley & Sons, Inc. Int J Quantum Chem, 2002
Photoinduced dissociation of electrospray‐generated ions in an ion trap/time‐of‐flight mass spectrometer using a pulsed CO2 laser
Authors: Gabryelski Wojciech , Li Liang
Published: October 2002

An ion trap/time‐of‐flight (IT/TOF) mass spectrometer was developed and applied to infrared multiphoton dissociation (IRMPD) studies of ions generated by electrospray ionization. A pulsed 10.6‐µm laser beam from a CO2 laser was used for excitation of trapped ions. Results from IRMPD of peptide ions show that this method provides useful information related to the amino acid sequence of analyzed peptides. Comparative studies show that IRMPD spectra are similar to those obtained using a 266‐nm UV laser beam for excitation. However, in contrast to multiple‐pulse excitation required at 266 nm, the energy of a single laser pulse in IRMPD is sufficient to induce dissociation of peptide ions. The laser power is practically an exclusive parameter that must be controlled in order to obtain IRMPD spectra that will provide the optimal structural information. It is further demonstrated that the IRMPD IT/TOF technique has the potential to probe the structural features of larger ions that cannot be readily fragmented by collision‐induced dissociation (CID). A multiply charged ion of equine cytochrome c is successfully fragmented in a single laser pulse experiment. The IRMPD IT/TOF technique is also shown to be a promising tool for studying dissociation kinetics of peptide and protein ions. Unlike other methods that usually monitor the dissociation ion kinetics in a dissociation time frame of greater than milliseconds, the IT/TOF can promptly detect all product ions generated by the dissociation process, and thus monitor the dissociation process of peptides and proteins in a sub‐millisecond time frame. This instrument allows us to determine the dissociation rates of cytochrome c ions using high‐energy photoexcitation. It is found that the charge state of the protein ion has a significant effect on dissociation kinetics, which is consistent with that found under low‐energy excitation experiments. It is shown that the increase in energy of a laser pulse from 130 to 180 mJ changes the dissociation rate constant for the +12 ion from k = 2.4 × 103 s−1 to k = 7.3 × 104 s−1. The +8 ion following excitation at 130 mJ dissociates slower with a rate constant of k = 2.6 × 102 s−1. The rate difference observed is attributed to conformational differences among the ions with different charge states. Copyright © 2002 John Wiley & Sons, Ltd.
Characterization of an insoluble polyimide oligomer by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry
Authors: Gies Anthony P. , Nonidez William K. , Anthamatten Mitchell , Cook Robert C. , Mays Jimmy W.
Published: October 2002

In the past two years, papers have appeared in the literature which demonstrate that matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectra can be obtained from matrix‐analyte preparations which have been produced by grinding the two materials together until a powder of small particle size is obtained. In the present study that methodology was modified and applied to an insoluble polyimide oligomer, poly(4,4′‐oxydiphenylenepyromellitimide) (POPM). Two matrix materials were employed in this analysis, 1,8 dihydroxyanthrone (dithranol) and 3‐aminoquinoline, with and without an additional cationizing agent. The spectra obtained by this method are shown to be sensitive to the matrix employed in the analysis as well as the quantity of cationizing agent combined with the matrix. Copyright © 2002 John Wiley & Sons, Ltd.
Metabonomics: the use of electrospray mass spectrometry coupled to reversed‐phase liquid chromatography shows potential for the screening of rat urine in drug development
Authors: Plumb Robert S. , Stumpf Chris L. , Gorenstein Marc V. , Castro‐Perez Jose M. , Dear Gordon J. , Anthony Maria , Sweatman Brian C , Connor Susan C. , Haselden John N.
Published: October 2002

The application of liquid chromatography/mass spectrometry (LC/MS) followed by principal components analysis (PCA) has been successfully applied to the screening of rat urine following the administration of three candidate pharmaceuticals. With this methodology it was possible to differentiate the control samples from the dosed samples and to identify the components of the mass spectrum responsible for the separation. These data clearly show that LC/MS is a viable alternative, or complementary, technique to proton NMR for metabonomics applications in drug discovery and development. Copyright © 2002 John Wiley & Sons, Ltd.
Modified Fenton's processes for effective in‐situ chemical oxidation—Laboratory and field evaluation
Authors: Kakarla Prasad K. , Andrews Thomas , Greenberg Richard S. , Zervas David S.
Published: October 2002

Fenton's reagent in its conventional form, although effective for contaminant treatment, is impractical
from an in‐situ field application perspective due to low pH requirements (i.e., pH 3‐4),
and limited reagent mobility when introduced into the subsurface. Modified Fenton's processes that use
chelated‐iron catalysts and stabilized hydrogen peroxide have been developed with the goal of promoting
effective in‐situ field application under native pH conditions (i.e., pH 5‐7), while
extending the longevity of hydrogen peroxide. Laboratory experiments conducted in soil columns packed with organic
soil to compare modified Fenton's catalysts with conventional catalysts (acidified iron
[II]) indicated superior mobility and sorption characteristics for modified Fenton's
catalysts. Furthermore, the acidic pH of a conventional catalyst was buffered to the native soil range, leading to
increased iron precipitation/adsorption following permeation through the soil column. The chelates present
within the modified Fenton's catalyst showed greater affinity toward iron compared with the native soil and,
hence, minimized iron loss through adsorption during the permeation process even at pH 5‐7.

Field effectiveness of the modified Fenton's process was demonstrated at a former dry‐cleaning
facility located in northeast Florida. Preliminary laboratory‐scale experiments were conducted on
soil‐slurry and groundwater samples to test the process efficacy for remediation of chlorinated solvents.
Based on successful experimental results that indicated a 94 percent (soil slurry) to 99 percent
(groundwater) reduction of cis‐1,2‐DCE, PCE, and TCE, a field‐scale treatment
program was initiated utilizing a plurality of dual‐zone direct push injection points installed in a grid
fashion throughout the site. Results of treatment indicated a 72 percent reduction in total chlorinated
contamination detected in the site groundwater following the first injection event; the reduction increased
to 90 percent following the second injection event. © 2002 Wiley Periodicals Inc.
Early stages of degradation of polysulphide sealants in an aqueous environment
Authors: Church Simon , Harris Steven J. , Rattana Acharawan , Watts John F.
Published: October 2002

Polysulphide sealants are now widely used to ensure the integrity of fuel tanks on both civil and military aircraft. The consequences of failure of such sealants are severe both in terms of the length of time that the aircraft will be removed from service and the nature of the remedial work that must be carried out within the tanks themselves.

It was against this background that a recent multi‐partner European Union Project MaSSPS (Materials System for Surface Protection and Sealing) was established. The members of the consortium include sealant manufacturers, aircraft manufacturers and other interested parties. The work to be presented in this paper concerns an extended study of the surface behaviour of candidate polysulphide sealant materials on exposure to water for times of up to 3 months.

Coupons of research‐grade sealants were immersed in ultrapure water at 25°C and 55°C in a thermostated water bath. These coupons were examined by XPS, using a Thermo VG Scientific Sigma Probe spectrometer with monochromated Al Kα radiation, and by ToF‐SIMS, using a VG Scientific Type 23 instrument equipped with a two‐stage reflectron analyser. Copyright © 2002 John Wiley & Sons, Ltd.
Use of optical methods to characterize thin silane films coated on aluminium
Authors: Franquet A. , Terryn H. , Bertrand P. , Vereecken J.
Published: October 2002

For corrosion and adhesion problems, the aluminium and its alloys are usually modified by different surface treatments. Silane coupling agents that are an alternative treatment for the chromate‐containing pretreatment are being used more frequently in industry. This paper focuses on the study of a no‐rinse system using the non‐functional silane bis‐1,2‐(triethoxysilyl)ethane (BTSE). The objective of this work is to study the effect of curing BTSE films coated on aluminium substrates. Spectroscopic ellipsometry is used to determine the thickness and optical constants of the silane coatings as a function of the curing conditions. It is shown by infrared spectroscopic ellipsometry (IRSE) how the curing causes changes in the chemistry of silane films deposited on aluminium. Indeed, IRSE combines the advantages of the traditional Fourier transform infrared spectroscopy method (molecular information via knowledge of the infrared absorption bands) with those of spectroscopic ellipsometry (morphological information such as film thickness and optical information such as refractive index and extinction coefficient). Copyright © 2002 John Wiley & Sons, Ltd.
Comparison of the self‐chemisorption of azurin on gold and on functionalized oxide surfaces
Authors: Schnyder B. , Kötz R. , Alliata D. , Facci P.
Published: October 2002

The formation of extended uniform protein monolayers by single‐ or multiple‐step self‐chemisorption was investigated on gold and on functionalized oxide surfaces. These protein layers were characterized by spectroscopic ellipsometry, x‐ray photoelectron spectroscopy (XPS) and scanning force microscopy (SFM). Chemisorption on oxygen‐terminated surfaces (SiO2, mica) was preceded by exposure of the surface to 3‐aminopropyltriethoxysilane and glutaric dialdehyde. On both substrates (gold and insulator) the protein layers appeared flat and robust under SFM imaging conditions. The thickness of the three‐layer structure (4.5 nm on mica), measured by engraving the layer with the SFM tip, matched fairly well with the value expected for the supramolecular architecture. The thickness could be verified after each chemisorption step by ellipsometry and XPS. The elements expected for the azurin layer (Cu and S in particular) were confirmed by XPS at both substrates. The multiple self‐chemisorption approach reported herein could be applicable to similar proteins, because it relies on the general principles of protein assembling. Copyright © 2002 John Wiley & Sons, Ltd.
Role of salts on the BSA adsorption on stainless steel in aqueous solutions. II. ToF‐SIMS spectral and chemical mapping study
Authors: Poleunis Claude , Rubio Céline , Compère Chantal , Bertrand Patrick
Published: October 2002

It is now well established that protein adsorption constitutes the first step of the mechanism leading to biofilm formation, which is a precursor of the biofouling. Biofouling is a major problem for any activity in seawater. In order to improve our basic knowledge of the biofilm formation mechanism, the role of salts, dissolved in natural seawater, on protein adsorption on a stainless steel surface have been investigated. Different aqueous solutions were used. They contained different salt mixtures and concentrations (NaCl alone, NaCl + MgCl2, NaCl + CaCl2 and artificial seawater), while keeping the total salt concentration the same as in natural seawater (36 g l−1). A protein, bovine serum albumin (BSA), was also added to the saline solutions at 20 mg l − 1 concentration. Stainless‐steel samples were immersed into the different aqueous solutions for 24 h. After rinsing in demineralized water and drying, the surface of these samples was analysed by time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS).

The ToF‐SIMS spectra showed an influence of the salts contained in the solutions on the protein adsorption. The role of CaCl2 seemed to be unfavourable whereas MgCl2 was rather favourable for BSA adsorption.

The ToF‐SIMS molecular mappings showed that all the salts dissolved in water produced micrometre particles at the sample surfaces. These particles mainly constituted Na+, Mg+ or Ca+. Because there was no space correlation with any counter‐ions (Cl−, SO4−, OH−, etc.), these particles were not salt residues. Moreover, these particles were found to be the preferential adsorption sites for the proteins. Indeed, the images show that BSA surrounds these metallic spots to form annular‐shaped patterns (diameter ϕ ∼ 20 µm). Copyright © 2002 John Wiley & Sons, Ltd.
Comparison of different procedures of biotin immobilization on gold for the molecular recognition of avidin: an FT‐IRRAS study
Authors: Pradier C.‐M. , Salmain M. , Liu Z. , Méthivier C.
Published: October 2002

In an attempt to build new, sensitive and easy to handle biosensors, we investigated different methods to immobilize biotin molecules at a gold surface and the subsequent molecular recognition of neutravidin. We compared a two‐step procedure: covalent binding of biotin to a previously chemisorbed ω‐functionalized thiolate monolayer; and direct chemisorption of a long‐chain biotinylated thiol. Fourier transform infrared reflection–absorption spectroscopy (FT‐IRRAS) was used to characterize the molecular films at each step. Subsequent binding of the protein neutravidin to each of these biotin layers was readily detected owing to labelling of the protein with an alkyne dicobalt hexacarbonyl complex, yielding characteristic mid‐infrared vC≡O signals that were shown to be sensitive to nanomolar concentrations of proteins in solution.

A fully covalent binding of biotin was achieved by first chemically modifying the biotin molecule to yield a long‐chain biotinylated thiol, followed by direct adsorption to the gold surface. The modification of biotin by a thiol bearing a side COOH function enabled full insertion of this molecule into the avidin binding pocket and prevented non‐specific interaction of the protein with the surface. Copyright © 2002 John Wiley & Sons, Ltd.
Corrosion protection of aluminium metal–matrix composites by cerium conversion coatings
Authors: Hamdy Abdel Salam , Beccaria Anna Maria , Traverso Pierluigi
Published: October 2002

Effect of cerium pretreatment on the corrosion inhibition characteristics of AA6061 T6 alloy–10% Al2O3 metal–matrix composite was investigated in aerated 3.5% NaCl solution after different immersion times ranging between 1 and 60 days at room temperature. Series of specimens were prepared under the following conditions: as‐polished; directly treated in CeCl3; alkaline etching followed by CeCl3 treatment; immersion in boiling water followed by CeCl3 treatment; and alkaline etching followed by immersion in boiling water and then CeCl3 treatment. Electrochemical impedance spectroscopy (EIS) was used to investigate the corrosion behaviour of treated and untreated specimens. The EIS was measured by perturbing the free corrosion potential of the specimens with 10 mV a.c. with a frequency decreasing from 10 mHz to 65 kHz. Polarization tests were used to investigate the perfect passivity domain after corrosion. Optical microscopy and SEM were used to investigate the occurrence of localized corrosion due to chloride ion attack. Specimens untreated, directly treated in CeCl3 and alkaline etched followed by CeCl3 treatment suffered from pitting as well as crevice corrosion after 30 days of immersion in NaCl. Conversely, the specimens after alkaline etching followed by oxide thickening in boiling water before cerium treatment showed promising corrosion protection even after 60 days of immersion in NaCl. The degree of protection depends to a high extent on the specimen preparation prior to cerium pretreatment. Copyright © 2002 John Wiley & Sons, Ltd.
Absolute energy calibration in Auger electron spectroscopy by using elastically backscattered primary electrons
Authors: Goto K. , Jiang Y. Z. , Nissa Rahman N. , Asano Y. , Shimizu R.
Published: October 2002

The feasibility of an absolute energy calibration in Auger electron spectroscopy has been studied by using elastically backscattered primary electrons with an accuracy of 15 meV(σ) for the energy range 10–1200 eV. Our novel prototype cylindrical mirror analyser (CMA) was further improved for this work. An electron gun with a special tungsten cathode should present well‐defined characteristics of primary electrons of constant shape in the energy distribution, irrespective of the acceleration voltage. The effects caused by the Wehnelt bias, space charge and cathode temperatures were examined. Thus, for the proper setting of the Wehnelt bias and cathode temperature, an ‘iteration’ method (between higher and lower energies) using a precision calibrated primary accelerating power supply was employed to obtain the transfer coefficient of the CMA. This is a self‐consistent method with automatic correction for work functions. Furthermore, a poor energy resolution of the CMA would shift the peak position in a spectrum as the result of a convolution of the actual spectrum with the analyser function, particularly for higher energies. Such peak shifts were simulated using an experimental spectrum. Copyright © 2002 John Wiley & Sons, Ltd.
XPS surface analyses of LaPO4 ceramics prepared by precipitation with or without excess of PO43−
Authors: Jørgensen Sissel , Horst Jens Anton , Dyrlie Oddvar , Larring Yngve , Ræder Henrik , Norby Truls
Published: October 2002

Lanthanum phosphate (LaPO4) powders were synthesized by precipitation with and without excess of phosphate and sintered at 1450° C. Bulk and surfaces of different origin and treatments were investigated using powder x‐ray diffraction, transmission electron microscopy and x‐ray photoelectron spectroscopy. The XPS data are reported and interpreted in some detail, and they indicate that phosphate excesses do remain in surfaces and appear to be accompanied by sodium accumulated in the surface from an unknown source. It is likely that grain boundaries are similarly phosphate enriched and a generally higher electrical conductivity of phosphate‐excess LaPO4 samples is discussed in view of this. Copyright © 2002 John Wiley & Sons, Ltd.
Surface and optical characterization of yttrium hydride films deposited on regular glass to be used as switchable mirrors
Authors: Velásquez P. , Castañer R. , de la Casa‐Lillo M. A. , Sánchez‐López M. M. , Mallavia R. , Moreno I. , Gutiérrez A. , Mateos F.
Published: October 2002

Yttrium and palladium thin films deposited on glass have been characterized by means of XPS depth profiling, SEM, energy‐dispersive x‐ray spectroscopy and ultraviolet–visible spectroscopy. These films allow optical windows of variable transparency to be obtained based on the formation of yttrium hydride by hydrogenation, with the palladium film working as a barrier against yttrium oxidation but being permeable to hydrogen. The transformation of yttrium into its hydride is concomitant with a metal–semiconducting transition that changes the physical properties of the material, especially its optical behaviour: the transmittance in the visible range goes from 0% for the metallic state to 30–70% for the hydrogenated state. In this work, the preparation conditions of optical windows using low‐cost regular glass as substrate have been optimized, both regarding the deposition and the hydrogenation. Uniform films free of impurities, such as oxygen and carbon, have been obtained under ultrahigh vacuum conditions of ∼10−7 Pa. Deposition has been performed by electron bombardment of the material, using palladium and yttrium of high purity. Copyright © 2002 John Wiley & Sons, Ltd.
Microchemical and micromorphological features of gunshot residue observed by combined use of AFM, SA‐XPS and SEM + EDS
Authors: D'Uffizi M. , Falso G. , Ingo G. M. , Padeletti G.
Published: October 2002

Microchemical and micromorphological analytical methods have been used by law enforcement agencies to ascertain whether or not an individual has been involved recently in a firearm shooting by determining the presence of gunshot residue (GSR).

In the present work, the microchemical and micromorphological features of the GSR particles deposited on the bullet and on the firing hands, collected using double‐sided tape, have been studied by means of the combined use of scanning electron microscopy + energy‐dispersive spectroscopy (SEM + EDS), atomic force microscopy (AFM) and selected‐area x‐ray photoelectron spectroscopy (SA‐XPS).

The results indicate that this advanced approach could disclose new micromorphological and microchemical features that could be useful for considerably increasing the confidence level of such determination. Copyright © 2002 John Wiley & Sons, Ltd.
X‐ray photoelectron spectroscopy study of thin oxide layers formed on (001)‐oriented β‐NiAl single‐crystal surfaces
Authors: Frémy Nicolas , Maurice Vincent , Marcus Philippe
Published: October 2002

Quantitative XPS data complemented by low‐energy electron diffraction (LEED) and scanning tunnelling microscopy (STM) results of the very first stages of oxidation of an NiAl(001) single‐crystal surface are reported. The thickness, stoichiometry and alloy composition at the oxide/alloy interface and, when possible, the structure have been analysed after oxidation at room temperature and 750°C and under 10−7, 10−5 and 200 mbar of oxygen. The growth of alumina layers is essentially two‐dimensional in the initial stages. Thin oxide films grown up to 50 Å show an oxygen enrichment that decreases with increasing thickness. The competition between the segregation of aluminium and its consumption by oxygen in the growth kinetics of the oxide layers is evidenced by the variation of the stoichiometry of the oxide films and alloy composition at the oxide/alloy interface. Copyright © 2002 John Wiley & Sons, Ltd.
Investigation of surface structure and composition ofin situannealed Fe–Mn binary alloy samples using RHEED and electron spectroscopy
Authors: Martínez C. , Cremer R. , Neuschütz D. , Servais J. P. , Loison D.
Published: October 2002

The formation of oxides at the surface of Fe–1.5%Mn and Fe–0.6%Mn binary alloys was investigated as a function of the conditions of the heat treatments. Both the influence of temperature and the atmosphere under which the experiments were performed were studied. The range of annealing temperatures was adjusted to 800°C. The atmosphere consisted of a mixture of N2–5%H2and traces of water vapour, with different fixed dew points ranging from −10°C to −30°C. The state of the annealed surfaces was determined usingin situanalytical devices attached to the annealing reactor in order to avoid surface contamination or the formation of native oxides after the experiments due to contact with air. The structure and composition of the surfaces were determined by reflection high‐energy electron diffraction (RHEED) and electron spectroscopy (XPS, AES). Copyright © 2002 John Wiley & Sons, Ltd.
Characterization of hydrous manganite (γ‐MnOOH) surfaces—an XPS study
Authors: Ramstedt M. , Shchukarev A. V. , Sjöberg S.
Published: October 2002

Crystalline manganite (γ‐MnOOH) has been synthesized and characterized using x‐ray diffraction and high‐resolution transmission electron microscopy techniques. The surface composition was studied with XPS between pH 0.4 and 11. Special pre‐cooling procedures were developed to keep the manganite/water interface intact before and during XPS measurements. The O/OH group ratio differs between pH 6 and 11, in agreement with the acid/base characteristics of the surface. Below pH 6, on the other hand, drastic changes can be seen in the O 1s spectra due to dissolution of manganite. Possibly the interaction of OH groups with H+ in acidic suspensions is a first step leading to dissolution. The surface charge arising at high and low pH is compensated by the counter‐ions Na+ and Cl−, respectively. The XPS spectra are presented and discussed in terms of the mechanisms for surface complexation and dissolution processes. Copyright © 2002 John Wiley & Sons, Ltd.
Use of spectroscopic ellipsometry to study Zr/Ti films on Al
Authors: Laha P. , Schram T. , Terryn H.
Published: October 2002

Spectroscopic ellipsometry in the spectral range between the near‐ultraviolet and the near‐infrared (250–1700 nm) (SE) and the mid‐infrared (2–23 µm) (IR‐SE) have been used for the characterization of various thin coatings on aluminium. Both SE and IR‐SE provide information concerning the morphological features of the coating, but owing to the presence of characteristic absorptions IR‐SE also reveals the chemical composition. This paper discusses the application of the developed optical models for the characterization of the more complex Zr/Ti‐based passivation coatings. The results obtained indicate that these coatings consist of a complex hydrated Zr/Ti/Al oxyfluoride. Copyright © 2002 John Wiley & Sons, Ltd.
Study of the NiTi/SiO2 interface: analysis of the electronic distributions
Authors: Jarrige Ignace , Jonnard Philippe , Frantz‐Rodriguez Nadège , Danaie Kamran , Bosseboeuf Alain
Published: October 2002

We present a study of the interface between a NiTi film deposited by magnetron d.c. sputtering and a SiO2 film obtained by thermal oxidation. Electron‐induced X‐ray emission spectroscopy (EXES) is used to characterize the physicochemical environment around the Si atoms at the NiTi/SiO2 interface, and to obtain information about the interfacial reactivity. From analysis of the Si 3p valence states, the composition and the thickness of the interfacial zone before and after annealing are deduced. The composition of the passivation layer, located at the surface of the metallic film, is determined by EXES and X‐ray Photoelectron Spectroscopy. Copyright © 2002 John Wiley & Sons, Ltd.