bluuebunny/crossref_metadata_2025 huggingface dataset:
Proton affinities of N—O anions and their protonated forms
Authors: Kazazić Saša , Kazazić Snježana P. , Klasinc Leo , McGlynn Sean P. , Pryor William A.
Published: October 2002

The proton affinities (PA) of several N—O anions, namely the singly charged anions nitrite, peroxynitrite, nitrate and peroxynitrate and the doubly charged anions cis‐ and trans‐hyponitrite and oxyhyponitrite, were calculated to be 1413.8, 1440.5, 1348.5, 1414.7, 2065.2, 1987.4 and 1977.9 kJ mol−1, respectively. The PA of the corresponding conjugate acids were 780.3, 749.8, 746.0, 724.7, 1394.9, 1448.9 and 1340.7 kJ mol−1, respectively. The PA of cis‐ and trans‐hyponitric and oxyhyponitric acid were 906.7, 723.8 and 728.2 kJ mol−1, respectively. Comparison with the available experimental values for the acids indicates that the calculated values are good estimates of these important quantities. Copyright © 2002 John Wiley & Sons, Ltd.
Synthesis and characterization of aromatic polyamides containing alkylphthalimido pendent groups
Authors: Ferrero E. , Espeso J. F. , de la Campa J. G. , de Abajo J. , Lozano A. E.
Published: October 2002

A series of polyisophthalamides containing pendent phthalimido groups and flexible side spacers were prepared from four novel diacids and three commercial aromatic diamines. These polyamides were prepared in high yields and with high molecular weights by direct polycondensation with triphenyl phosphite and pyridine as condensing agents. The weight‐average and number‐average molecular weights, measured by gel permeation chromatography, were 70,000–137,000 and 47,000–86,000 g/mol, respectively. The novel polyamides were amorphous and readily soluble and showed glass‐transition temperatures of 150–240 °C, as measured by differential scanning calorimetry. Thermogravimetric analysis showed that the 10% weight‐loss temperatures in nitrogen were 355–430 °C, a significant improvement in thermal stability having been observed with the increase in the side‐chain length. A theoretical quantum mechanical study was successfully carried out to explain these results. Flexible and tough films, cast from polymer solutions, showed tensile strengths of 50–125 MPa. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3711–3724, 2002
Effects of the structure and morphology of zinc glutarate on the fixation of carbon dioxide into polymer
Authors: Meng Y. Z. , Du L. C. , Tiong S. C. , Zhu Q. , Hay Allan S.
Published: October 2002

Zinc glutarates were synthesized from zinc oxides with varying purities via different stirring routes. The particle size and structure of these zinc glutarates were determined by wide‐angle X‐ray diffraction, transmission electron microscopy, and the laser particle size analyzer technique. The results demonstrated that the crystallinity and crystalline perfectness of zinc glutarate are the crucial factors that affect the catalytic activity for the copolymerization of carbon dioxide (CO2) and propylene oxide (PO). Additionally, the catalyst with a small particle size dramatically increased the yield of the copolymerization between CO2 and PO. High‐molecular‐weight and regular molecular structure poly(propylene carbonate)s (PPC)s were obtained from CO2 and PO with the synthesized zinc glutarates. Very high catalytic activity of 160.4 g polymer/g catalyst was afforded. The NMR technique revealed that the PPC copolymer exhibits an exact alternating copolymer structure. The relationships between the crystallinity and the particle size of catalyst with the catalytic activity are correlated and discussed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3579–3591, 2002
Dimethyldioxirane as a new and effective oxidation agent for the epoxidation of α,ω‐di(isobutenyl)polyisobutylene: A convenient synthesis of α,ω‐di(2‐methyl‐3‐hydroxypropyl)‐polyisobutylene
Authors: Kéki Sándor , Nagy Miklós , Deák György , Lévai Albert , Zsuga Miklós
Published: October 2002

The synthesis and characterization of α,ω‐di(2‐methyl‐2,3‐epoxypropyl)polyisobutylene are reported. The epoxidation of α,ω‐di(isobutenyl)polyisobutylene was achieved at room temperature with dimethyldioxirane, which proved to be a very effective reagent for epoxidation without the formation of byproducts. A very good agreement was found for the conversion determined by 1H NMR and matrix‐assisted laser desorption/ionization mass spectrometry (MALDI HMS). The epoxy end groups were converted quantitatively into aldehyde termini with zinc bromide as a catalyst. The aldehyde groups were then reduced with LiAlH4 into primary hydroxyl functions to obtain α,ω‐di(2‐methyl‐3‐hydroxylpropyl)polyisobutylene with high efficiency. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3974–3986, 2002
Novel block ionomers II. Synthesis and characterization of polyisobutylene‐based block cationomers
Authors: Fang Zheng , Kennedy Joseph P.
Published: October 2002

Various novel block cationomers consisting of polyisobutylene (PIB) and poly[2‐(dimethylamino)ethyl methacrylate] (PDMAEMA) segments were synthesized and characterized. The specific targets were various molecular weight diblocks (PIB‐b‐PDMAEMA+) and triblocks (PDMAEMA+‐b‐PIB‐b‐PDMAEMA+), with the PIB blocks in the DPn = 50–200 range (number‐average molecular weight = 3,000–9000 g/mol) connected to blocks of PDMAEMA+ cations in the DPn = 5–20 range (where DP is the number‐average degree of polymerization). The overall synthetic strategy for the preparation of these block cationomers had four steps: (1) synthesis by living cationic polymerization of mono‐ and diallyltelechelic polyisobutylenes, (2) end‐group transformation to obtain PIBs fitted with termini capable of mediating the atom transfer radical polymerization (ATRP) of DMAEMA, (3) ATRP of DMAEMA, and (4) quaternization of PDMAEMA to PDMAEMA +I− by CH3I. Scheme 1 shows the microarchitecture and outlines the synthesis route. Kinetic and model experiments provided guidance for developing convenient synthesis methods. The microarchitecture of PIB–PDMAEMA di‐ and triblocks and the corresponding block cationomers were confirmed by 1H NMR and FTIR spectroscopy and solubility studies. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3679–3691, 2002
Synthesis of novel ladder polymers of poly(3,4‐dihydro‐2H‐pyran‐2‐methanol)
Authors: Abdelaal Magdy Youssef
Published: October 2002

Polydi(3,4‐dihydro‐2H‐pyran‐2‐methyl) esters of oxalic, adipic, and phthalic acids were prepared at different temperatures in the presence of different cationic initiators, namely, the boron trifluoride/diethyl ether complex system, anhydrous ferric chloride, and p‐toluene sulfonic acid. The obtained polymers were hydrolyzed under basic conditions, and the polydispersity indices of these polymers were determined before and after hydrolysis. The results are discussed to shed some light on the ability to use this analysis to investigate the precise structure of the obtained polymers and to predict the ability of these polymers to form ladder or semiladder polymers. Characteristics of such polymers were dependent, to some extent, on the type of crosslinks and the cationic initiators used for polymerization as well as the reaction temperature. It seems possible to optimize the conditions leading to formation of ladder or semiladder polydi(3,4‐dihydro‐2H‐pyran‐2‐methyl) esters of oxalic acid and adipic acid, respectively. The ladder structure was confirmed through determination of the polydispersity index before and after hydrolysis of the polymer formed at different temperatures and through computer‐aided molecular modeling. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3909–3915, 2002
Modified cubic spherosilicates as macroinitiators for the synthesis of inorganic–organic starlike polymers
Authors: Holzinger Dieter , Kickelbick Guido
Published: October 2002

Modified cubic spherosilicate cages of the type [Si8O20]8− were used as rigid, inorganic cores for the synthesis of macroinitiators for thermal and photoinduced free radical and controlled radical polymerizations. Two different routes to these macroinitiators were investigated: the direct modification of the octaanion with chlorosilane‐functionalized initiators and the hydrosilation of SiH‐substituted cages. The latter synthesis of the macroinitiators resulted in more defined reaction products. With these compounds, the polymerizations of styrene and methyl methacrylate were carried out. The free radical polymerizations showed broad polydispersities based on coupling reactions, whereas the copper‐mediated atom transfer radical polymerizations (ATRP) revealed that good polymerization control could be achieved with the prepared initiators. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3858–3872, 2002
Synthesis of π‐conjugated oligomer that can form metallo polymers
Authors: El‐Ghayoury Abdelkrim , Schenning Albertus P. H. J. , Meijer E. W.
Published: October 2002

An oligo(p‐phenylene vinylene) that contains terpyridine ligands has been synthesized. Upon addition of metal ions, a π‐conjugated metallo polymer is formed in which the well‐defined character of oligomers and the material properties of polymers are combined. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4020–4023, 2002
Emulsion polymerization of divinyl monomers stabilized by sodium dodecyl sulfate and bis(2‐ethylhexyl)sulfosuccinate sodium salt
Authors: Gawdzik Barbara , Maciejewska Małgorzata
Published: October 2002

The emulsion polymerization of divinyl monomers is investigated. Emulsions were obtained in the presence of sodium dodecyl sulfate and bis(2‐ethylhexyl)sulfosuccinate sodium salt as surfactants. The influence of monomer type and kind of surfactant on the particle size distribution is studied. The porous structure of the broken emulsions is also determined. The results indicate that the diameter of nanospheres obtained from two divinyl monomers are significantly larger than those obtained from polystyrene. Aggregation of the particles and the pore‐forming diluent added to the emulsion are responsible for the existence of pores. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3967–3973, 2002
Effect of central spacer chain structure on cationic cyclopolymerization tendency of divinyl ethers
Authors: Hashimoto Tamotsu , Ohashi Minoru , Kodaira Toshiyuki
Published: October 2002

To clarify the effects of the central spacer chain structure of divinyl ethers on their cationic cyclopolymerization tendencies, 1,4‐bis[(2‐vinyloxy)ethoxy]benzene (1), 1,4‐bis[(2‐vinyloxy)ethoxy]butane (2), 1,6‐bis[(2‐vinyloxy)ethoxy]hexane (3), 1,8‐bis[(2‐vinyloxy)ethoxy]octane (4), and 1,4‐bis[(4‐vinyloxy)butoxy]butane (5) were polymerized with the hydrogen chloride/zinc chloride (HCl/ZnCl2) initiating system in methylene chloride (CH2Cl2) at 0 °C at low initial monomer concentration ([M]0 = 0.15 M). The polymerizations of divinyl ethers 2 and 3 gave soluble polymers quantitatively. In contrast, the polymerizations of divinyl ethers 1, 4, and 5 underwent gel formation at high monomer conversion. The content of the unreacted vinyl groups of the obtained soluble polymers was measured by 1H NMR spectroscopy. Judging from the relatively low vinyl contents of the polymers produced even in the early stage of the polymerization (monomer conversion < ∼20%), the cyclopolymerization occurred to some extent for 2, 3, and 4. On the contrary, the polymers produced from 1 and 5 exhibited the relatively high vinyl content, indicating that the cyclopolymerization tendencies of 1 and 5 were lower than those of 2, 3, and 4. These results are discussed in terms of the structural variety of the spacer chains: (1) the presence of benzene ring (1 vs 2), (2) their length (2 vs 3 and 4), and (3) the position of ether oxygen (4 vs 5). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4002–4012, 2002
Preparation and characterization of N‐methyl‐substituted polyurethane
Authors: Choi Hee‐Sung , Noh Si‐Tae
Published: October 2002

We prepared N‐methyl‐substituted polyurethanes with different substitution degrees from sodium hydride, methyl p‐toluene sulfonate, and polyether–polyurethane containing poly(oxytetramethylene) glycol, 4,4′‐diphenylmethane diisocyanate, and 1,4‐butanediol. The chemical structures were characterized with Fourier transform infrared and 1H NMR. To investigate the effects of the N‐substitution degree on the morphology, thermal stability, and mechanical properties, we used differential scanning calorimetry, thermogravimetric analysis, and a universal testing machine. As the substitution degree increased, the new free (1708 cm−1) and bonded (1650 cm−1) carbonyl peaks increased. There was no bonded carbonyl peak in fully substituted polyurethane because the urethane groups had no hydrogen. At a small substitution degree, we observed a slight increase in the glass‐transition temperature and decrease in the endotherms of soft‐segment and hard‐segment domains due to the decrease in the hard‐segment domain and the increase in the urethane groups in the soft‐segment domain. The hard‐segment domain decreased and then disappeared as the N‐methyl substitution degree increased. These changes in the morphology resulted (1) in decreased modulus and tensile strength for the films because of the decrease in physical crosslinking points and (2) improved thermal stability as the substitution degree increased. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4077–4083, 2002
Dehydrocoupling and Diels–Alder reactions on siloxane polymers
Authors: Kim Chungkyun , Kwark Kyungran
Published: October 2002

Dehydrocoupling reactions between linear poly(methylhydrosiloxane) {Me3SiO–[MeSi(H)O]n–SiMe3} and alcohols such as cholesterol, anthracene‐9‐carbinol, (12‐crown‐4)‐2‐carbinol, pyrene‐1‐carbinol, 4‐methyl‐5‐thiazoleethanol, and 4‐pyridilpropanol were introduced under catalytically mild conditions. The degrees of conversion of SiH bonds in polysiloxane were monitored with 1H NMR spectra. The reaction of the 9‐methoxyanthracene adduct on siloxane polymers and maleimide derivatives (maleimide, N‐ethylmaleimide, and maleic acid anhydride) produced [2+4]‐cycloadducts in very high yields. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4013–4019, 2002
Structural polymorphism in poly(dodecamethylen‐di‐O‐methyl‐L‐tartaramide)
Authors: Iribarren Laco José Ignacio
Published: October 2002

Structural characterization of poly(dodecamethylen‐di‐O‐methyl‐L‐tartaramide) was carried out with optical microscopy, thermal analysis, X‐ray diffraction, and electron microscopy. Two different crystalline forms were found in accordance with the thermograms, powder and fiber X‐ray diffraction diagrams. The electron microscopy allows corroboration of the morphological and crystallographic differences. Molecular modeling was used to conclude the structural analogies and differences between the two crystalline forms that were related to the chain packing and orientation in the crystal cell, respectively. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2523–2530, 2002
Persistent pulmonary interstitial emphysema in an unventilated neonate
Authors: Gürakan Berkan , Tarcan Aylin , Arda Irfan Serdar , Coşkun Mehmet
Published: October 2002

Persistent pulmonary interstitial emphysema (PPIE) is a chronic form of pulmonary interstitial emphysema. The disease is histologically distinguished by large cysts and giant cells. Our patient was a female twin who was born at 31 weeks of gestation with a birth weight of 1,450 g. A chest X‐ray at 2 hr after delivery was normal. At 12 hr, respiratory distress developed, and nasal continuous positive airway pressure (CPAP) was initiated. A chest film revealed left‐sided pneumothorax. A chest tube was inserted, and the baby continued on nasal CPAP for 5 days. Her chest X‐ray on postnatal day 4 showed diffuse cystic changes in the left lung. Thoracic computed tomography revealed multiple thick‐walled cysts, the largest measuring 3 cm in diameter. Our case confirms that localized PIE may occur in preterm infants who have been treated with nasal CPAP only. Since this method is being used increasingly to avoid mechanical ventilation and in the postextubation period, it is very important that clinicians be aware of its complications. Pediatr Pulmonol. 2002; 34:409–411. © 2002 Wiley‐Liss, Inc.
Differential expression of 17β‐hydroxysteroid dehydrogenase isozyme genes in prostate cancer and noncancer tissues
Authors: Koh Eitetsu , Noda Toru , Kanaya Jiro , Namiki Mikio
Published: October 2002

BACKGROUND

The adrenal steroids dehydroepiandrosterone and androstenediones are converted into active androgen testosterone in prostatic tissues. Different 17β‐hydroxysteroid dehydrogenase (17βHSD) isozymes are characterized by either oxidation or reduction reactions. These redox reactions represent an important step in both biosynthesis and metabolism of androgens. This study presents the differential expression of 17βHSD isozyme genes in cancerous and noncancerous prostate tissues of in vivo samples.

METHODS

Thirty‐four fresh specimens of transrectal prostatic needle biopsy were obtained; 11 were pathologically diagnosed as adenocarcinoma and 23 as without malignancy. The gene expression levels of five isozymes (type 1–5) of 17βHSD were evaluated. The quantification of gene expression was assessed by means of the real‐time polymerase chain reaction.

RESULTS

The expression levels of the type 3 17βHSD gene with malignancy were significantly higher than those in prostatic tissues without malignancy, and those of type 2 17βHSD with malignancy were significantly lower than those in nonmalignant tissues. There were no significant differences in 17βHSD type 1, type 4, and type 5 gene expression in cancerous and noncancerous tissues.

CONCLUSION

Our results suggest that 17βHSD type 2 and type 3 play an important role in the conversion of adrenal steroids into potential androgens in prostate cancer tissue. Prostate 53: 154–159, 2002. © 2002 Wiley‐Liss, Inc.
Searching for quantitative entropy‐enthalpy compensation among protein variants
Authors: Beasley James R. , Doyle Donald F. , Chen Lixin , Cohen David S. , Fine Bryan R. , Pielak Gary J.
Published: October 2002

Entropy‐enthalpy (SH) compensation occurs when a small change in ΔG is caused by large, and nearly compensatory, changes in ΔH and ΔS. It is considered a ubiquitous property of reactions in water. Because water is intimately involved in protein stability, SH compensation among protein variants, if it exists, could lead to important knowledge about protein‐water interactions. In light of recent theoretical work on SH compensation, we gathered thermodynamic data for >200 protein variants to seek evidence for the simplest quantitative model of SH compensation (i.e., The van't Hoff denaturation enthalpy divided by the van't Hoff denaturation entropy is a constant). We conclude that either the data are insufficient to support the idea that quantitative SH compensation is a general feature of variant proteins or that such compensation does not exist. This study reinforces the idea that ΔH‐versus‐ΔS plots should not be used to provide evidence for SH compensation. Proteins 2002;49:398–402. © 2002 Wiley‐Liss, Inc.
Molecular diagnostic procedures for production of pathogen‐free propagation material
Authors: Manulis Shulamit , Chalupowicz Laura , Dror Orit , Kleitman Frida
Published: October 2002

Production of disease‐free propagation material is a major means of controlling most bacterial diseases of plants, particularly when neither resistant clones nor effective chemical treatments are available. For this purpose sensitive, specific and rapid detection methods are required. The advent of molecular biology and, in particular, the polymerase chain reaction (PCR) has opened new ways for the characterization and identification of plant pathogens and the development of disease‐management strategies. PCR‐based detection methods rely on the development of primers for the specific detection of the pathogen. The use of pathogenicity genes as targets for primer design is the preferred procedure for obtaining specific primers but other procedures may also be useful for this purpose. In the present review we describe four examples of procedures for detecting four important bacterial pathogens in Israel: Erwinia herbicola pv gypsophilae in gypsophila, Xanthomonas campestris pv pelargonii in geranium, Agrobacterium tumefaciens in asters and roses, and Xanthomonas campestris pv campestris in crucifers. Procedures for constructing specific PCR primers for each bacterium are illustrated and discussed as well as the combination of PCR with other methods.

© 2002 Society of Chemical Industry
An over‐current protection module for telephone network line cards—an analysis of electro‐thermal properties
Authors: Zarnik Marina Santo
Published: October 2002

In this paper the results of a finite‐element analysis of the electro‐thermal behaviour of an over‐current protection thick‐film hybrid module are presented. The module was designed for protecting the line card of a telephone network against an abnormal surge of current, resulting from accidental shorts between adjacent power feed lines. The switching time of the device is crucial to its effectiveness as a protective element. A transient finite‐element thermal analysis was performed in order to predict the dynamic temperature states at the critical points of the circuit design and to evaluate the influence on the switching characteristics. A comparison between simulated and practical results is given. Copyright © 2002 John Wiley & Sons, Ltd.
A theory of excitation–energy transfer regarded as nonadiabatic transition and its comparison to Förster's theory
Authors: Okuno Yoshishige , Mashiko Shinro
Published: October 2002

We propose a rate‐constant expression for an excitation–energy transfer between two molecules that is regarded as a nonadiabatic transition between two adiabatic electronic states. It is shown that under weak intermolecular interaction the approximately derived rate constant increases with the increase in pseudo‐Coulombic interaction \documentclass{article}\pagestyle{empty}\begin{document}$\langle \phi_{e}^{A}\phi_{g}^{B}|H|\phi_{g}^{A}\phi_{e}^{B}\rangle_{\mathbf{r}}$\end{document} and depends on the differences in the potential energies and the potential derivatives of the initial and final electronic states. In addition, the rate constant under strong interaction is shown to decrease with increasing pseudo‐Coulombic interaction. We show that our expression has the advantage that it can be applied to the excitation–energy transfer under the (not very) weak and the strong coupling limits which cannot be addressed by Förster's theory. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Theoretical analysis of cyclic reaction mechanisms of two ethylenes
Authors: Sakai Shogo
Published: October 2002

The reaction mechanisms of cyclic addition of two ethylenes were investigated by ab initio molecular orbital methods. The treated pathways were two supra‐supra [2s + 2s] with D2h or C2v symmetries and one supra‐antara [2s + 2a] with C2 symmetry. These are concerted reactions and lead to the product cyclobutane directly. These reaction pathways were analyzed on the basis of simple electron configuration models by the CiLC‐IRC method. The [2s + 2s] reaction of D2h occurs in a very small region near the transition state, and the [2s + 2s] reaction of C2v occurs in two steps. However, there are no energy minimum points between these steps. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
1,5‐hydrogen shifts in methyl‐1,3‐cycloheptadienes
Authors: Hess B. Andes
Published: October 2002

Density functional calculations are performed on the isomeric methlyl‐1,3‐cycloheptadienes and the transition structures that link them via 1,5‐hydrogen shifts. A total of 18 stationary points were located, 10 minima and 8 transition structures. Many of the structures found are related conformationally. The results indicate that the isomerizations previously observed experimentally arise from antarafacial 1,5‐hydrogen shifts. The calculated relative energies and activation energies are in satisfactory agreement with those observed by Mironov. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Potential energy surface and ro‐vibrational energies of Ne in the ground electronic state
Authors: Šindelka Milan , Špirko Vladimír , Urban Jan , Mach Pavel , Leszczynski Jerzy
Published: October 2002

A global potential energy surface of Ne in its ground electronic state is evaluated using a Rayleigh–Schrödinger version of the third‐order multireference many‐body perturbation theory (MR‐MBPT) in a complete model space. The ab initio data are fitted quantitatively to a model potential energy function expressed in the Jacobi coordinates, and the fitted function is used to evaluate the ro‐vibrational energies of Ne using the (bond length–bond angle) Sutcliffe–Tennyson (ST) and (hyperspherical) Yamashita–Morokuma–Leforestier (YML) approaches. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Static dipole and quadrupole polarizability of confined hydrogen atom with Z=N/3 (N=1–5)*
Authors: Sen K. D. , Mayer B. , Schmidt P. C. , Garza Jorge , Vargas Rubicelia , Vela Alberto
Published: October 2002

First calculations of static dipole and quadrupole polarizability for the spherically confined hydrogen atom within the hard boundaries with nuclear charge Z=N/3, N=1–5, are carried out using the Sternheimer perturbation‐numerical procedure. The polarizability values strongly depend upon the radius of confinement. The polarizability calculations for the exotic hydrogenic ions with nuclear charges ⅓, ⅔, \documentclass{article}\pagestyle{empty}\begin{document}$\frac{4}{3}$\end{document}, and \documentclass{article}\pagestyle{empty}\begin{document}$\frac{5}{3}$\end{document} exhibit strong dependence on the radius of confinement and the nuclear charge. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Toward a computed peptide structure database: The role of a universal atomic numbering system of amino acids in peptides and internal hierarchy of database
Authors: Chass Gregory A. , Sahai Michelle A. , Law Jacqueline M. S. , Lovas Sandor , Farkas Ödön , Perczel Andras , Rivail Jean‐Louis , Csizmadia Imre G.
Published: October 2002

With the construction and implementation of a logical and standardized numbering of atomic nuclei, to define mono‐, di‐, and oligo‐peptide systems, automation of input file generation and data extraction could greatly improve the efficiency of the search for the structural energy minima on the potential energy hypersurface of these systems. The internal hierarchy of the database covering constitutional structures, protective groups, levels of theory, and basis sets used, as well as the variety of possible conformations, is also discussed. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
A generalized expansion of the potential energy of diatomic molecules
Authors: Molski Marcin , Konarski Jerzy
Published: October 2002

A new generalized expansion of the Born–Oppenheimer potential energy of diatomic molecules, combining a power series with Padé approximant, is introduced. It converges in the range of internuclear separation R∈〈0,∞) and can be used to reduce infrared and microwave spectra to parameters of a diatomic effective Hamiltonian. © 2002 John Wiley & Sons, Inc. Int J Quantum Chem, 2002
Magnetic‐field manipulation of chemical bonding in artificial molecules
Authors: Yannouleas Constantine , Landman Uzi
Published: October 2002

The effect of orbital magnetism on the chemical bonding of lateral, two‐dimensional artificial molecules is studied in the case of a 2e double quantum dot (artificial molecular hydrogen). It is found that a perpendicular magnetic field reduces the coupling (tunneling) between the individual dots and, for sufficiently high values, it leads to complete dissociation of the artificial molecule. The method used is building on Löwdin's work on projection operators in quantum chemistry; it is a spin‐and‐space unrestricted Hartree–Fock method in conjunction with the companion step of the restoration of spin and space symmetries via projection techniques (when such symmetries are broken). This method is able to describe the full range of couplings in two‐dimensional double quantum dots, from the strong‐coupling regime exhibiting delocalized molecular orbitals to the weak‐coupling and dissociation regimes associated with a generalized valence bond combination of atomic‐type orbitals localized on the individual dots. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Benzocyclobutadiene: The question of structures, magnetic shieldings, and aromatic character*
Authors: Jensen Morten Østergaard , Thorsteinsson Thorstein , Hansen Aage E.
Published: October 2002

The importance of electron correlation for structure and magnetic shielding of benzocyclobutadiene is studied using the [2,2]‐CASSCF, the [8,8]‐CASSCF, and the MP2 approaches. The study aims at the question of applicability of the terms aromatic or antiaromatic for classification of this system and at the assignment of the experimental hydrogen chemical shifts. As reference, results for benzene are also included. Optimized structures are reported, including the two, respectively, three roots at the two complete active space self‐consistent field (CASSCF) levels. For the ground state, electron correlation plays about the same role for structure and energy as it does for benzene, while the magnetic properties are sensitive to correlation, and are not entirely resolved at the present levels. The higher CASSCF roots correspond to inherently multiconfigurational states, and the magnetic results for the second molecular state indicate the necessity for higher level computations. The chemical shifts computed for the ground state are compatible with the experimental data, in contrast to a previous assignment associating the shifts with a molecular structure representing the second CASSCF root. Applying a criterion based on the perpendicular component of the shielding field, the ground state of benzocyclobutadiene qualifies for neither a global aromatic nor a global antiaromatic assignment. In a dichotomic classification, the six‐membered ring again qualifies for neither an aromatic nor an antiaromatic assignment, leaving open an antiaromatic assignment for the four‐membered ring, in accord with the reactivity of benzocyclobutadiene. We compare and discuss the assignments proposed here and in the literature in the light of a prevailing feeling of elusiveness shading the concept of aromaticy. © 2002 John Wiley & Sons, Inc. Int J Quantum Chem, 2002
Stochastic diagonalization of Hamiltonian: A genetic algorithm‐based approach
Authors: Nandy Subhajit , Chaudhury Pinaki , Bhattacharyya S. P.
Published: October 2002

We propose and demonstrate the workability of a genetic‐algorithm‐based technique of finding the eigenvalues and eigenfunctions of a real symmetric Hamiltonian matrix. The algorithm can be tailored to extract all the eigenvalues at a time or to extract only the lowest or the highest eigenvalue first and then sequentially determine the next few higher (lower) eigenvalues. The algorithm is generalized to handle diagonalization problems in which the basis functions themselves are optimized simultaneously. Several model applications are reported. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Effects of size of noncovalent complexes on their stability during collision‐induced dissociation
Authors: Jellen Emily E. , Chappell Angelina M. , Ryzhov Victor
Published: October 2002

The size‐dependent stability of noncovalent complexes under collision‐induced dissociation (CID) conditions was studied on a quadrupole ion trap mass spectrometer. Complexes of heme, tetraphenylporphyrin iron(III) (TPP‐Fe), and tetraphenylporphyrin manganese(III) (TPP‐Mn) with several histidine‐containing peptides and model compounds were formed by electrospray ionization (ESI) and their stability was probed by variable‐energy CID. It was found that the stability of complexes with the same (or nearly the same) binding energy has a linear dependence on the complex size (or total number of degrees of freedom). This approach will allow comparisons of variable‐energy CID data for noncovalent complexes with different binding energies and could be used to help in structural elucidation of some complexes formed by multidentate ligands. The linearity of size effects on the stability of the complexes was also tested in three crown ether/protonated primary amine systems. Copyright © 2002 John Wiley & Sons, Ltd.
Multiple sprayer system for high‐throughput electrospray ionization mass spectrometry
Authors: Schneider Bradley B. , Douglas D. J. , Chen David D. Y.
Published: October 2002

A multiple sprayer electrospray ion source for high‐throughput analysis is described. The ion source is comprised of multiple electrospray capillaries, each with an ion lens located near the tip. The electric potentials applied to the ion lenses are used to control the sprayers. The use of ion lenses eliminates the need for mechanical blocking devices to selectively enable or disable the sprayers, and results in a less expensive and more reliable set‐up. Sprayers can be enabled or disabled within approximately 50–250 ms when the lens potentials are controlled manually. For simultaneous operation of multiple electrospray capillaries, it is advantageous to orient the capillaries so that the spray from each passes directly in front of the entrance aperture of the mass spectrometer. Copyright © 2002 John Wiley & Sons, Ltd.
Liquid chromatography/mass spectrometric bioanalysis of a modified γ‐cyclodextrin (Org 25969) and Rocuronium bromide (Org 9426) in guinea pig plasma and urine: its application to determine the plasma pharmacokinetics of Org 25969
Authors: Epemolu Ola , Mayer Iain , Hope Frank , Scullion Paul , Desmond Paul
Published: October 2002

A sensitive and specific liquid chromatography/mass spectrometry (LC/MS) method has been developed and validated for the quantification of the modified γ‐cyclodextrin Org 25969 and Rocuronium bromide (Roc or Org 9426) in the plasma and urine of guinea pigs. The assay was linear and reproducible over the range 25–10000 ng/mL for both compounds. The lowest limit of quantification (LLOQ) for both compounds in urine was 25 ng/mL. In plasma, the LLOQ was 25 ng/mL for Org 9426 and 50 ng/mL for Org 25969. The inter‐ and intra‐day variation was lower than 20%. The physicochemical properties of both compounds imposed different modes of extraction from plasma. The modified γ‐cyclodextrin was extracted by trifluoroacetic acid (TFA) precipitation while Rocuronium was extracted by acetonitrile precipitation. Both compounds were quantified in urine by direct injection onto the column. The LC/MS analyses of Org 25969 and Org 9426 were performed using two different assay conditions. It was not possible to quantify the complex of cyclodextrin and Roc as it dissociated on the LC column. The use of LC/MS conferred great advantage to the quantification of both Org 25969 and Org 9426, as they were not chromogenic enough to afford the sensitivity and specificity required for the assay. Copyright © 2002 John Wiley & Sons, Ltd.
Characterization of fluoropolymer films deposited by magnetron sputtering of poly(tetrafluoroethylene) and plasma polymerization of heptadecafluoro‐1‐decene (HDFD) on (100)‐oriented single‐crystal silicon substrates
Authors: Zhang Yan , Yang G. H. , Kang E. T. , Neoh K. G. , Huang Wei , Huan A. C. H. , Lai D. M. Y.
Published: October 2002

Fluoropolymer thin films have been deposited on (100)‐oriented single‐crystal silicon substrates via argon plasma sputtering of a poly(tetrafluoroethylene) (PTFE) target and plasma polymerization of 1H, 1H, 2H‐heptadecafluoro‐1‐decene (HDFD). The surface composition and molecular structure of the deposited fluoropolymer films were analysed by x‐ray photoelectron spectroscopy (XPS), time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) and Fourier transform infrared (FTIR) spectroscopy. The ToF‐SIMS spectrum of the sputter‐deposited PTFE (s‐PTFE) surface revealed a high concentration of oligomeric –(CF2)‐ segments, resembling that of the pristine PTFE surface. However, the ToF‐SIMS spectra of the plasma‐polymerized HDFD (pp‐HDFD) films showed the presence of oligomeric –(CF2)‐ segments with much shorter repeat units, in comparison with those of the pristine PTFE and s‐PTFE film. The XPS and FTIR results suggested that the surface composition and chemical structure of the pp‐HDFD film deposited at a high r.f. power were closer to those of the s‐PTFE film. Water contact angle and atomic force microscopy measurements indicated that both sputtering deposition and plasma polymerization could give rise to highly hydrophobic surfaces with good uniformity. Peel adhesion test results suggested that both the s‐PTFE and pp‐HDFD films were strongly tethered to the surface of Si substrates. Copyright © 2002 John Wiley & Sons, Ltd.
Nanoscale bimetallic catalysts: are they really bimetallic?
Authors: Guczi L. , Bazin D. , Schay Z. , Kovács I.
Published: October 2002

The existence of bimetallic particles (and their reducibility and location on/or in the support) in Ru–Co/NaY and Pt–Co/NaY samples has been studied by in situ X‐ray adsorption spectroscopy (XAS). It is established that in Ru–Co/NaY the monometallic clusters maintain their identity, whereas in Pt–Co/NaY the existence of small bimetallic particles can be established. In both cases the results are supported by other techniques, such as XPS and temperature‐programmed reduction. Copyright © 2002 John Wiley & Sons, Ltd.
Synthesis and ionic exchanges of zeolites for gas adsorption
Authors: Beyaz Kayiran S. , Lamari Darkrim F.
Published: October 2002

The present study deals with hydrogen adsorption on forms of the sodium LTA (Na A) zeolite fully exchanged by potassium and lithium, and on their compacted forms. The Na A zeolite was synthesized by using the hydrothermal method, and its ionic exchange was obtained by successive contacts. Structural characterizations were evaluated using different methods. Adsorption isotherms were measured for hydrogen in Na A and in its exchanged forms at a temperature of 293 K and up to a pressure of 1 MPa. In this paper, we investigated the infrared spectroscopy of fully exchanged materials. The structure of the materials and their hydrogen adsorption capacity varied with the nature of the cations exchanged. Copyright © 2002 John Wiley & Sons, Ltd.
XPS characterization of adsorbed reaction intermediates on automotive exhaust gas catalysts: NO and CO + NO interactions with Pd
Authors: Mamede A.‐S. , Leclercq G. , Payen E. , Granger P. , Gengembre L. , Grimblot J.
Published: October 2002

Nitrous oxide (NO) adsorption and the CO + NO reaction have been investigated on bulk and alumina‐supported Pd catalysts by XPS at various temperatures between 25 and 300°C with PNO in the 0.5–5.0 (×10−2) atm range and PCO = 5 × 10−3 atm. A catalytic reactor settled in the preparation chamber coupled to the spectrometer allows surface changes occurring under catalytic conditions on these catalysts to be characterized. Various nitrogen‐containing species have been detected, which depend on the oxidation state of Pd. The results have been explained tentatively in the light of a mechanism proposed for NO transformation. Copyright © 2002 John Wiley & Sons, Ltd.
Ag, Ge and Sn reference samples for elastic peak electron spectroscopy (EPES), used for experimental determination of the inelastic mean free path and the surface excitation parameter
Authors: Gurban S. , Gergely G. , Menyhard M. , Adam J. , Adamik M. , Daroczi Cs. , Toth J. , Varga D. , Csik A. , Gruzza B.
Published: October 2002

Reference samples are needed for experimental determination of the inelastic mean free path (IMFP) of electrons by elastic peak electron spectroscopy (EPES). High‐quality (microcrystalline mirror) Ni reference samples were used for IMFP measurements. For surface excitation parameter experiments, new types of reference samples are needed. They should exhibit pronounced surface‐loss spectra, such as amorphous Ge (aGe), Sn and Ag. A new procedure is presented for their preparation. Microcrystalline Ag and Sn reference samples were deposited on highly polished (by Buehler alumina alpha micropolish 1C) brass (60% Cu, 40% Zn) substrates. Electrolytic deposition was used for Ag and for Sn and resulted in excellent surface quality. The average surface roughness rav was checked by scanning tunnelling microscopy or atomic force microscopy before and after Ar+ ion bombardment cleaning. Typical rav values were 4–6 nm for Ag, 3–4 nm for Sn and 2–4 nm for brass substrate. The aGe sample was deposited by magnetron sputtering or by evaporation in a high vacuum on an Si substrate. Its rav was 4–5 nm. The samples were studied by EPES/reflection electron energy‐loss spectroscopy, covering the 0.2–5 keV energy range, with the ESA 31 HSA electron spectrometer. The IMFP of Sn was determined by EPES. The surface excitation parameters for the Si, Ge and Sn samples were determined from their inelastic scattering cross‐section spectra. For Ag the surface excitation parameter was estimated by using the above reference samples. Copyright © 2002 John Wiley & Sons, Ltd.
XPS study of living tree
Authors: Shchukarev Andrei , Sundberg Björn , Mellerowicz Ewa , Persson Per
Published: October 2002

X‐ray photoelectron spectroscopy (XPS) was used to study the distribution of elements and main wood components (cellulose and lignin) within the wood and at the bark/wood interface of a living hybrid aspen stem. The hybrid aspen was grown upright in a greenhouse and then tilted at ∼45° to induce tension wood formation and upright bending of the stem. The wood between the pith and the bark on the upper side of the tilted stem was analysed. Changes in the middle lamella/S1 layer chemical composition, which corresponded to the transition from normal wood produced during upright stem growth to tension wood produced upon stem tilting, were observed. Such changes were related to the lower lignin and higher cellulose/hemicellulose contents in the tension wood. A non‐uniform radial distribution of nitrogen (amino acids, proteins) within the stem was also noted. At the bark/wood interface the presence of inorganic elements (Ca, K and P) and a significant increase in nitrogen were found. The opposite wood side of the tree was enriched in lignin and fatty acids. It was shown that application of XPS imaging to a very rough surface of wood split allows the inhomogeneous lateral lignin distribution to be visualized. Copyright © 2002 John Wiley & Sons, Ltd.
Grain boundary segregation in Ni–Sb alloy polycrystals
Authors: Lejček Pavel , Rar Andrei , Hofmann Siegfried
Published: October 2002

In order to compare the grain boundary segregation of antimony and sulphur in bi‐ and polycrystals, the chemical composition of grain boundaries was studied by AES on fracture surfaces of polycrystalline Ni–Sb alloy (0.485 at.% Sb, 0.003 at.% S) samples annealed in the temperature range 773–1173 K. In contrast to the previously studied {133} bicrystals, dominant antimony segregation was observed at the grain boundaries of samples annealed in the above temperature range. By quantification of the AES results, the temperature dependence of grain boundary composition was determined and correlated with the Guttmann model of interfacial solute segregation in multicomponent systems. Consideration of various levels of grain boundary saturation and mutual interactions enabled the determination of the values of segregation enthalpy $(\Delta H^{0}_{Sb} = - 63\,\hbox{kJ mol}^{-1}, \Delta H^{0}_{S} = - 70\,\hbox{kJ mol}^{-1})$ and entropy $(\Delta S^{0}_{Sb} = - 20\,\hbox{J } (\hbox{mol}^{-1}\hbox{K}^{-1}), \Delta S^{0}_{S}= +12\,\hbox{J } (\hbox{mol}^{-1}\hbox{K}^{-1}))$ of both segregants. Extraordinarily high values of antimony concentration were detected at grain boundaries of bicrystals as well as polycrystals after annealing at high temperatures. It is highly probable that an extended two‐dimensional precipitation of nickel antimonides at grain boundaries occurs during the corresponding heat treatment. Copyright © 2002 John Wiley & Sons, Ltd.
Surface nanotextures on aluminium
Authors: Caicedo‐Martinez C. E. , Koroleva E. V. , Thompson G. E. , Skeldon P. , Shimizu K. , Habazaki H. , Hoellrigl G.
Published: October 2002

Chemical polishing and electropolishing of aluminium result in fine cellular textures of nanometre dimensions, which play a role in the electrochemical behaviour of aluminium and its response to further treatment processes such as conversion coating and anodizing. Concerning the latter, the surface texture is highlighted by porous anodic film growth for protection of the substrate. The influence of residual impurities and low additions of alloying elements on the development of the textures is investigated here for superpure aluminium (99.99%) and an Al–0.4wt.%Mn alloy, respectively. Complementary analytical approaches, including atomic force microscopy and transmission electron microscopy, disclose scalloped cellular textures comprising adjacent peaks and troughs, with a dependence on the grain orientation of the aluminium substrate. In addition to texture development, enrichment of copper impurity in the alloy occurs adjacent to the alloy/oxide film interface, as revealed by in‐depth elemental profiles generated by r.f. glow discharge optical emission spectroscopy. The absence of similar enrichments of iron and silicon in the alloy suggests that these elements are distributed mainly as fine segregates in the aluminium, unlike copper, which is in solid solution. At low alloying levels, manganese reveals limited enrichment and is also probably present mainly as segregates. The origin of the textures and their dependence on grain orientation are thus considered to be related to the presence and location of relatively high‐melting‐point elemental impurities in the alloy and their local electrochemical responses relative to the adjacent alloy surface. Copyright © 2002 John Wiley & Sons, Ltd.
In situ analysis using synchrotron radiation photoemission spectroscopy for initial oxidation of oxygen preadsorbed Si(001) surfaces induced by supersonic O2 molecular beams
Authors: Yoshigoe Akitaka , Teraoka Yuden
Published: October 2002

By means of synchrotron radiation photoemission spectroscopy we have performed in situ analyses for initial oxidation of oxidized Si(001) surfaces induced by supersonic O2 molecular beams. In the Si 2p, Si 2s and valence band photoemission spectra with an angle integrated mode, the O2 chemisorption processes induced by the O2 translational energy of 3.0 eV were clarified as a function of the exposure time. The Si2+ oxidation states, as well as Si1+, rapidly increased and then gradually decreased as a function of the O2 dose. However, Si4+ continued increasing gradually from the initial exposure. We found that the O2 incident energy of 3.0 eV directly induced oxidation in the backbond of the second Si layer. Copyright © 2002 John Wiley & Sons, Ltd.