bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractAnalytical 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

AbstractThis 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

AbstractMost 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

AbstractBond 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

AbstractAn 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

AbstractIn 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

AbstractThe 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

AbstractFenton'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

AbstractPolysulphide 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

AbstractFor 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

AbstractThe 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

AbstractIt 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

AbstractIn 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

AbstractEffect 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

AbstractThe 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

AbstractLanthanum 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.