bluuebunny/crossref_metadata_2025 huggingface dataset:
Theoretical analysis of pyrrole anions addition to carbon disulfide and carbon dioxide
Authors: Kobychev Vladimir B. , Vitkovskaya Nadezhda M. , Zaytseva Irina L. , Larionova Elena Yu. , Trofimov Boris A.
Published: August 2002

Quantum chemical analysis (MP2/6‐31+G*) of the pyrrole anions addition to carbon disulfide and the substitution effects therein shows that pyrrole‐2 (5)‐carbodithioates are thermodynamically the most stable compounds, while 1‐isomer obtained from the unsubstituted pyrrole is likely a kinetic product. Steric hindrances destabilize N‐adducts when a methyl substituent appears in a 2(5) position and the 2,5‐dimethyl‐1‐pyrrolecarbodithioate anion turns out to be even less stable than the 2,5‐dimethyl‐3‐pyrrolecarbodithioate anion. By contrast, pyrrole‐1‐carboxylates are calculated to be the most stable adducts of CO2 with pyrrole anions. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Polymorphism of hydrogen bonding in the short double helixes of oligonucleotides: Semiempirical quantum chemical study
Authors: Kabanov Artem V. , Komarov Vladislav M.
Published: August 2002

The origin of heterogeneity of nucleotide steps geometry in short double helixes is studied theoretically. By using the semiempirical MNDO/PM3 technique, the stability of “propeller‐like” and “step‐like” forms of base H‐pairing is examined in the structure of oligonucleotide duplexes of different types. The influence of end effects on the process of nucleotides packing, as well as the dependence of duplex curvature on the nature of bonded oligonucleotides, are examined. It is concluded that the structural polymorphism of base pairs most likely determines the unique packing of complementary pairs and their flexibility in DNA structure. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Theoretical investigations of 1,4‐butanediol and 2‐butene‐1,4‐diol cyclodehydration using postprocessing visualization of quantum chemical calculation data
Authors: Fleisher M. , Stonkus V. , Leite L. , Lukevics E.
Published: August 2002

Cyclodehydration of 1,4‐butanediol and 2‐butene‐1,4‐diol to the corresponding cyclic ethers was studied using the AM1 semiempirical method. It was established that the cyclodehydration reaction of 1,4‐butenediol and 2‐butene‐1,4‐diol is effected by converting of semicyclic conformers in the presence of acidic and basic active centers. The calculation results indicate that a concerted mechanism is probably realized in the cyclodehydration of both diols, while the sequences of the predicted steps in the cyclodehydration reaction for 1,4‐butanediol and 2‐butene‐1,4‐diol are different. The calculated reaction heats for 1,4‐butanediol and 2‐butene‐1,4‐diol transformations are −184.029 and −308.746 kcal/mol, respectively. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Preopening of the DNA base pairs
Authors: Kryachko Eugene S. , Volkov Sergey N.
Published: August 2002

The lower‐energy stable structures of the A⋅T base pair are revealed under a search of its potential energy surface in the vicinity of its Watson–Crick configuration performed at the PM3 computational level. Their properties and the mutual position of the nucleic acid bases A and T in these structures allow to partition them into three classes: partially preopened, stretched, and fully preopened. The preferable monohydration sites of the preopened, stretched, and fully preopened pairs are also determined. It is demonstrated, first, that the monohydration of the A⋅T pair at particular sites favors a base pair preopeness and, second, that a binding of the water molecule to the preopened A⋅T base pair on the major groove side enhances its stabilization. It is also shown that water molecule placing in the vicinity of the central H bond of the A⋅T pair significantly facilitates its preopening. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 82: 193–204, 2001
Theoretical studies of cyclopropylsilylenes: The structures and stability of cyclopropylsilylene C3H5SiH
Authors: Feng Shengyu , Feng Dacheng
Published: August 2002

Ab initio molecular orbital calculations at the G2(MP2) level have been carried out on cyclopropylsilylene C3H5SiH. Four equilibrium structures were located. Like H2Si, the ground state of C3H5SiH is singlet and the triplet is the low‐lying excited state. The singlet–triplet separation energy is 127.9 kJ/mol. The cis‐trans isomerization path of singlet cyclopropylsilylene was investigated by intrinsic reaction coordinate (IRC) calculations. The calculations show that no gauche conformers exist along the potential energy curve of the cis‐trans isomerization and the isomerization happens with a barrier of 30.1 kJ/mol. Changes (ΔH and ΔG) in thermodynamic functions, equilibrium constant K(T), and A factor and reaction rate constant k(T) in Eyring transition state theory of the cis‐trans isomerization were also calculated. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Importance of frontier orbital interactions in addition reaction of water to disilene
Authors: Takahashi Masae , Veszprémi Tamás , Kira Mitsuo
Published: August 2002

Addition mechanisms of water to disilene were investigated in detail using the high level ab initio molecular orbital (MO) theory. We have found that the search for transition states by ab initio MO calculations combined with the frontier MO theory provides a good perspective view of the mechanisms of the reaction of disilenes and water. The initial electrophilic and nucleophilic interactions of the water with disilene give the corresponding weak complexes, CE and CN, which leads to the next nucleophilic and electrophilic attack of the water part, respectively. The latter pathway requires an antarafacial approach, while the former pathway proceeds via suprafacial addition. Whereas in the model disilene–water addition reaction, the pathway from CE is more favorable than the pathway from CN, the stereochemical ambiguity of the addition reactions found experimentally may be explained by the competition of the two pathways. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem 84: 192–197, 2001
Combined computational and experimental investigations on the diastereoselective hydrogenation of steroids by chiral oxazaborolidine
Authors: Göndös Gy. , Pálinkó I.
Published: August 2002

In this work the results of semiempirical quantum chemical calculations are described that support experimental findings applying the methyl derivative of oxazaborolidine‐BH3 chiral complex for the reduction of a number of pregnane derivatives (3α‐hydroxy‐5β‐pregnane‐20‐one, 3α,17α‐dihydroxy‐5β‐pregnane‐20‐one, 3α,21‐dihydroxy‐5β‐pregnane‐20‐one, and 3α,17α,21‐trihydroxy‐5β‐pregnane‐20‐one). Calculations were performed by the MNDO method. The reactants, the products, the assumed transition states, as well as the assumed intermediate structures were optimized without any constraints. Calculations were able to reproduce the observed activity sequence and explain the experimental finding that the thermodynamically less stable isomer is formed preferentially. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem 84: 253–258, 2001
Gas‐phase acidity of proline from density functional computations
Authors: Marino T. , Russo N. , Tocci E. , Toscano M.
Published: August 2002

Density functional computations using the B3LYP hybrid potential coupled with the extended 6‐311++G** basis set were performed to evaluate gas‐phase acidity of proline α‐amino acid. The computed value of gas‐phase acidity is 1403.8 kJ/mol in good agreement with the experimental counterpart (1395.0±13.8 kJ/mol) and is referred to the deprotonated species deriving from the first relative minimum of neutral proline characterized by the exo ring conformation with the carboxyl group in cis position. The most stable neutral proline isomer gives rise to a species for which the gas‐phase acidity value (1384.5 kJ/mol) is also close to the experimental data. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem 84: 264–268, 2001
A density functional study of the interconversion of carbonyls and alcohols in solution: Comparison of reaction mechanisms involving NADPH, histidine, and tyrosine
Authors: Várnai Péter , Richards W. Graham
Published: August 2002

Several reaction mechanisms for the interconversion of carbonyls and alcohols in solution are examined. The model system includes acetaldehyde, 1‐methyl‐1,4‐dihydropiridine as a hydride donor, and either 4‐methyl‐phenol or 4‐methyl‐imidazolium as a possible proton donor. This system is of relevance to understanding the catalytic mechanism of many oxidoreductase enzymes which use NADPH cofactor and tyrosine or histidine as general acids. The energetic changes are evaluated by constrained geometry optimization using density functional theory (B3LYP/6‐31+G*) coupled to a Poisson–Boltzmann solvation scheme. The results show that a stepwise mechanism with an initial hydride transfer to the aldehyde is favored for both proton donors over the alternative stepwise mechanism, in which there is an initial proton transfer to the aldehyde. The possibility of a concerted mechanism is also considered, but the corresponding activation energy exceeds those of the stepwise processes. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem 84: 276–281, 2001
Three conformers observed and characterized in 1‐hexyne
Authors: Atticks Karissa , Bohn Robert K. , Michels H. Harvey
Published: August 2002

The microwave spectrum of 1‐hexyne (n‐butyl acetylene) reveals the presence of three conformers that have been carefully characterized. 1‐Hexyne can be viewed as propane with terminal ethynyl and methyl substituents. These substituents can be arranged in anti–anti (AA), anti–gauche (AG), gauche–anti (GA), gauche–gauche (GG cis), and gauche–gauche′ (GG trans) conformations. The first three conformers are those observed experimentally and their rotational constants have been determined. The GG conformers, in both cis and trans arrangements have not been positively identified to date. We have determined the structural parameters and energies of all five possible conformations through ab initio quantum mechanical calculations at the HF, MP2, and B3LYP levels of theory. The calculated energies of these five conformers are very close, and a change in the relative stability of these conformers is found at different levels of theory. We find that inclusion of electron correlation effects is critical to our understanding of the energy ordering of these conformers. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
High‐resolution analysis of a 144‐membered pyrazole library from combinatorial solid phase synthesis by using electrospray ionisation Fourier transform ion cyclotron resonance mass spectrometry
Authors: Schmid Dietmar G. , Grosche Philipp , Jung Günther
Published: August 2002

A compound library consisting of 144 pyrazole carboxylic acids and six sublibraries consisting of 24 components was analysed using electrospray ionisation Fourier transform ion cyclotron resonance mass spectrometry (ESI‐FTICR‐MS). The library was synthesised by the split‐mix method and investigated by direct infusion analysis by which 134 compounds were detected. FTICR‐MS is predestined for the direct characterisation of complex compound libraries because of its outstanding mass resolution and mass accuracy. However, discrimination within the electrospray ionisation process sometimes leads to signal suppression and thus to misinterpretation of the synthetic results. Using micro‐HPLC/MS we were able to assign all 144 compounds including all pairs of isobaric pyrazoles. We also show that, due to partial separation, FTICR‐MS is indispensable for proper detection of co‐eluting compounds. Copyright © 2001 John Wiley & Sons, Ltd.
Electrospray ionization in the study of sol‐gel processes: the polycondensation of Ti(O‐n‐Bu)4 in the presence of Si(OEt)4
Authors: Cristoni Simone , Armelao Lidia , Gross Silvia , Tondello Eugenio , Traldi Pietro
Published: August 2002

The polycondensation of Ti(O‐n‐Bu)4 in presence of Si(OEt)4 (Et = C2H5, Bu = C4H9) has been studied by electrospray ionization of their mixtures in methanol. Series of oligomers due to Ti(OMe)4 (Me = CH3) polycondensation have been detected and represent the most abundant species. This result can be explained by the ready alcoholysis of Ti(O‐n‐Bu)4 and by its fast kinetics of oligomerization. However a series of Ti,Si‐containing oligomers, with molecular weights in the range 400–1300 Da, has also been detected. Their structures have been characterized by isotopic cluster analysis and MS/MS experiments, proving that they originate by reaction of Ti‐OH and Si‐OEt moieties. Copyright © 2001 John Wiley & Sons, Ltd.
The solvent shells of cluster ions produced by direct electric field extraction from glycerol/water mixtures
Authors: Balakin A. A. , Dodonov A. F. , Novikova L. I. , Talrose V. L.
Published: August 2002

Electric field extraction of gaseous negative ions directly from water/glycerol solutions by use of a track membrane technique was investigated. The distributions of numbers of solvent molecules in the extracted cluster ions for different compounds were obtained. It is shown that the extraction mechanism is a direct field‐stimulated evaporation of cluster ions from liquid, with a subsequent loss of several solvent molecules in the vacuum. For relatively simple ions a good correspondence of results was obtained with a continuous medium model. It was found that the number of solvent molecules in a cluster shell, for more complicated ions such as amino acids, is significantly greater than that for halide ions or ions of simple organic acids. An increase in the number of solvent molecules in the case of amino acid negative ions is rationalized in terms of the existence of several charged groups, each of which gives an additional contribution to the cluster shell. Copyright © 2001 John Wiley & Sons, Ltd.
Simultaneous determination of betamethasone and dexamethasone residues in bovine liver by liquid chromatography/tandem mass spectrometry
Authors: Van den hauwe O. , Perez J. Castro , Claereboudt J. , Peteghem C. Van
Published: August 2002

In this study a new method for the simultaneous confirmation of betamethasone and dexamethasone residues in bovine liver is presented. A Quattro LCZ triple quadrupole mass spectrometer, equipped with an atmospheric pressure ionization (API) source, was coupled to a high performance liquid chromatograph (HPLC) system. Spiked liver samples were first extracted with acetonitrile, and the extracts were purified on C‐18 columns. LC separations were performed on a Hypercarb column, with acetonitrile/water (90:10, v/v, +0.3% formic acid) as the mobile phase. Retention times for dexa‐ and betamethasone were 6.60 and 8.50 min, respectively. Fluorometholone had a retention time of 6.70 min and was used as the internal standard. The detection of the analytes was performed in the multiple reaction monitoring (MRM) mode. The assay was linear over the range of 0.5 to 8 µg/kg for both analytes. The estimated determination limits were 0.2 µg/kg for both beta‐ and dexamethasone and the quantification limits were 0.4 µg/kg for dexamethasone and 0.3 µg/kg for betamethasone. Analysis precision at 1, 2 and 4 µg/kg was lower than 6.1% (relative standard deviation, RSD) and accuracy was at least 97.5%. Recoveries at 1, 2 and 4 µg/kg ranged between 56 and 69%. Copyright © 2001 John Wiley & Sons, Ltd.
Detection of chlordanes by positive ion chemical ionization in an ion trap: a comparitive study of the non‐conventional reagents acetonitrile, acrylonitrile and dichloromethane
Authors: Zencak Zdenek , Oehme Michael , Skopp Sonja
Published: August 2002

The detection of some chlordane compounds (heptachlor, cis‐/trans‐chlordane and cis‐/trans‐nonachlor) by positive ion chemical ionization (PICI) in an ion trap was studied using acetonitrile, acrylonitrile and dichloromethane as non‐conventional reagent gases. These reagent gases initiated specific fragmentation reactions and resulted in different response factors. All reagent gases enabled detection limits in the low‐pg range for heptachlor, whereas the detection limits of cis‐/trans‐chlordane and cis‐/trans‐nonachlor were in the mid‐pg range. Additionally, the acetonitrile and dichloromethane PICI mass spectra of the cis‐ and trans‐stereoisomers of chlordane and nonachlor were different. Copyright © 2001 John Wiley & Sons, Ltd.
Violation of frozen shell approximation in dissociative electron capture by halogenated anthraquinones
Authors: Asfandiarov N. L. , Fal'ko V. S. , Lukin V. G. , Nafikova E. P. , Pshenichnyuk S. A. , Fokin A. I. , Lomakin G. S. , Chizhov Yu. V.
Published: August 2002

A series of halogenated anthraquinone (AQ) derivatives has been studied by means of electron capture negative ion (NI) mass spectrometry (ECNI‐MS). 1Cl‐AQ and 2Br‐AQ display dramatically steep positive temperature dependencies of Hal− ion abundance in the low electron energy region. Molecular NI intensity decreases rapidly with increasing temperature in the case of 1I‐AQ. In the case of 2Br‐AQ, a metastable NI peak (m/z 22.9) corresponding to the process BrAQ− → Br− + AQ0 was recorded. This means that the characteristic dissociation lifetime of the molecular NI Br‐AQ− is at least ∼25 µs at the energy ∼0.67 eV in the low‐temperature spectrum (T ∼80 °C), and at the energy ∼0.13 eV in the hot spectrum (T ∼290 °C). Together with the observed temperature dependence of the 2Br‐AQ curves of effective yield (CEY), this proves that this anion dissociates according to Coulson's model. The same halogen anion behavior is observed in the case of 1Cl‐AQ. There are three consecutive stages in the process of molecular NI dissociation of Cl‐ and Br‐substituted AQ, namely, electron capture into the empty π‐orbital by means of the shape resonance mechanism, followed by a radiationless transition into the ground electronic π‐state of the anion, as predicted by Compton in the case of the parabenzoquinone molecule, and, finally, a fluctuative dissociation of the molecular NI accompanied by the transition from the π‐term into the σ‐term, so‐called predissociation. Calculations show reasonable agreement with the experimental data. In the case of 1I‐AQ, an effect of inversion of empty levels in the process of electron capture by the molecule takes place, a violation of the so‐called frozen shell approximation. The phenomenon found may be of significance not only in the case of ECNI‐MS, but also in other experimental investigations using low‐energy electron‐molecule and ion‐molecule collisions. Copyright © 2001 John Wiley & Sons, Ltd.
Conformational changes in β‐endorphin as studied by electrospray ionization mass spectrometry
Authors: Lin Hui , Dass Chhabil
Published: August 2002

Because of a wide range of physiological functions, the structure of β‐endorphin (BE) is of great interest. In this study, conformational changes in BE induced by methanol are explored with electrospray ionization‐mass spectrometry (ESI‐MS). Differences in the charge‐state distribution (CSD) and the extent of hydrogen/deuterium (H/D) exchange were used to monitor the conformational changes. The latter experiments were conducted via time‐resolved ESI‐MS in a continuous‐flow apparatus. Both these techniques demonstrate that BE exists in a random coil open structure in aqueous media, but it acquires a more compact conformation with increased concentration of methanol. The H/D exchange experiments reveal that BE forms 61% α‐helix in mixed solvents. Copyright © 2001 John Wiley & Sons, Ltd.
A method for the identification of the double‐bond position of isomeric linear tetradecenols and related compounds based on mass spectra of dimethyl disulfide derivatives
Authors: Yuan Gu , Yan Jichao
Published: August 2002

A simple method is presented for calculation of the double‐bond position in linear tetradecenols based on mass spectral data of dimethyl disulfide derivatives. In this approach, the m/z ratios of the molecular ion and of one (or both) of the two most abundant fragment ions were utilized to calculate the double‐bond position, without the requirement to identify both fragment ions resulting from carbon‐carbon cleavage across what was originally the double bond. The approach was tested with mass spectra of dimethyl disulfide derivatives of 12 isomeric tetradecenols, and the double‐bond position in each isomer was successfully identified by this method. The method was shown to work also for the corresponding acetates. Copyright © 2001 John Wiley & Sons, Ltd.
Application of sulfur as a matrix for laser desorption/ionization in the characterization of halogenated fullerenes
Authors: Streletskiy Alexey V. , Kouvitchko Igor V. , Esipov Stanislav E. , Boltalina Olga V.
Published: August 2002

The application of sulfur as a matrix for matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS) analysis of highly chlorinated and fluorinated fullerenes is reported. Control over fluorofullerene fragmentation which resulted in the domination of the molecular peak C60F36− was achieved, with the optimal matrix‐to‐analyte ratio found to be 1000:1. We suggest the possible mechanism of the molecular ion formation according to the charge transfer between the sulfur anions and C60F36. For the first time the LDI and MALDI mass spectra of the highly chlorinated fullerene C60Clx(xmax ≈ 32) are presented. The formation of odd chlorine ions (positive and negative) is observed. We conclude that use of sulfur as a matrix leads to a significant decrease in fragmentation of the halogenated fullerenes. Copyright © 2001 John Wiley & Sons, Ltd.
Fine structure of the stability diagram and the amplitude of ion oscillation within hyperboloidal mass spectrometers
Authors: Sheretov Ernst P. , Philippov Igor V. , Karnav Tatiana B. , Fedosov Edgar V. , Ivanov Vladimir W.
Published: August 2002

This article shows that the dependence of the amplitude of ion oscillation within a hyperboloidal mass spectrometers (HMS) as a function of working point location on the stability diagram (in this case all working points lie at one scan line) exhibits a structure with spikes: the amplitude decreases drastically in some points and these dips look like ‘reversed spikes’. It is shown that the dips appear at particular values of the stability parameter, β0, that correspond to intersections of the scan line with lines of parametric resonances (quasi‐stability lines) described by us previously. This effect governs the trapping efficiency of ions injected into a radio‐frequency ion trap from an external source. Copyright © 2002 John Wiley & Sons, Ltd.
Differential isotopic mass splitting as a mass spectrometric tool for identifying protease substrates
Authors: McKeown Stephen C. , Heudi Olivier , Kay Corinne , Marshall Peter
Published: August 2002

A method is described whereby stable isotopic signatures were partially incorporated into both termini of a peptide sequence giving rise to a characteristic cluster of four peaks in the mass spectral analysis. Cleavage of this peptide by a protease between the labeled positions generates two fragments both displaying their own individual signature peaks. The event of protease cleavage of the peptide was monitored by the changes in clusters within the spectrum. We believe that this technique could be used to aid the discovery of new cleavage substrates for proteases. Additionally, the analysis can be automated with dedicated software designed to select and interpret the data since all peaks of interest contain predefined signatures and can be easily distinguished from background noise. Copyright © 2002 John Wiley & Sons, Ltd.
Tri‐α‐naphthylbenzene as a crystalline or glassy matrix for matrix‐assisted laser desorption/ionization: a model system for the study of effects of dispersion of polymer samples at a molecular level
Authors: Bauer Barry J. , Guttman Charles M. , Liu Da‐wei , Blair William R.
Published: August 2002

Tri‐α‐naphthylbenzene (TαNB) can exist as either a crystalline or glassy solid at ambient temperatures, making it a unique matrix in matrix‐assisted laser desorption/ionization (MALDI) spectroscopy. Electrosprayed TαNB is crystalline and has a melting point of 180 ± 2 °C, as measured by differential scanning calorimetry (DSC). A glass of TαNB is obtained upon heating above the crystalline melting point with a glass transition temperature of 68 ± 2 °C having no remaining crystallinity. MALDI samples containing mass fraction 1% polystyrene (PS) are run in both the crystalline and amorphous states. In the crystalline state, there is a strong spectrum typical of PS, but upon melting and quenching to the glassy state, the MALDI signal disappears. If the transparent, amorphous sample is treated with 1‐butanol, it becomes white, and the MALDI signal returns. DSC shows that the 1‐butanol treatment leads to the return of some of the crystallinity. Small angle neutron scattering (SANS) shows that the crystalline state has large aggregations of PS while the amorphous state has molecularly dispersed PS molecules. MALDI gives strong signals only when there are large aggregations of polymer molecules, with individually dispersed molecules producing no signal. Published in 2002 by John Wiley & Sons, Ltd.
On the sample‐complexity of ℋ︁∞ identification
Authors: Venkatesh S. R. , Dahleh M. A.
Published: August 2002

In this paper we derive the sample complexity for discrete time linear time‐invariant stable systems described in the ℋ︁∞ topology. The problem set‐up is as follows: the ℋ︁∞ norm distance between the unknown real system and a known finitely parameterized family of systems is bounded by a known real number. We can associate, for every feasible real system, a model in the finitely parameterized family that minimizes the ℋ︁∞ distance. The question now arises as to how long a data record is required to identify such a model from noisy input–output data. This question has been addressed in the context of l1, ℋ︁2 and several other topologies, and it has been shown that the sample‐complexity is polynomial. Nevertheless, it turns out that for the ℋ︁∞ topology the sample‐complexity in the worst case can be infinite. Copyright © 2001 John Wiley & Sons, Ltd.
On the structure of clique‐free graphs
Authors: Prömel Hans Jürgen , Schickinger Thomas , Steger Angelika
Published: August 2002

Using a clever inductive counting argument Erdős, Kleitman and Rothschild showed in 1976 that almost all triangle‐free graphs are bipartite, i.e., that the cardinality of the two graph classes is asymptotically equal. In this paper we investigate the structure of the “few” triangle‐free graphs which are not bipartite. As it turns out, with high probability, these graphs are bipartite up to a few vertices. More precisely, almost all of them can be made bipartite by removing just one vertex. Almost all others can be made bipartite by removing two vertices, and then three vertices and so on. We also show that similar results hold if we replace “triangle‐free” by K𝓁+1‐free and “bipartite” by 𝓁‐partite. © 2001 John Wiley & Sons, Inc. Random Struct. Alg., 19, 37–53, 2001
Analysis of the x‐ray photoelectron energy‐loss background in silicides
Authors: Castle J. E. , Salvi A. M. , Guascito M. R.
Published: August 2002

Intermetallic compounds provide a means to investigate the mutual influence of two elements on the photoelectron fine structure and background that have developed as a result of bond formation. In the case of the aluminides we have shown that aluminium acquires a background structure that is typical of elements having a 3d valence band and concluded that there is a strong ‘d’ component in the bonding structure arising from pd hybridization. In this paper we report a similar analysis of the background structure in two silicides, MoSi2 and FeSi2.

Both silicon and molybdenum in MoSi2 are very similar in background structure to that in their respective pure elemental states. Moreover, the plasmon structure that appears is similar to that of silicon itself. Thus we conclude that in this material ‘p’ character is an important feature of the bond. In the case of FeSi2 the situation is different. Here, silicon gains a pronounced background step, similar to that of iron, and the plasmon structure becomes weaker. This behaviour is analogous to that of FeAl and we conclude that this is evidence of the participation of the ‘d’ states of iron in bond formation. Copyright © 2001 John Wiley & Sons, Ltd.
Scanning force microscopy of DNA metallization
Authors: Seidel Ralf , Mertig Michael , Pompe Wolfgang
Published: August 2002

The nucleation and growth of platinum nanoparticles at single DNA molecules, leading to a template‐directed formation of micrometre‐long cluster chains, is investigated by scanning force microscopy (SFM). The cluster chains are synthesized by incubation of DNA with K2PtCl4 and subsequent chemical reduction of the platinum complexes. Scanning force microscopy is applied for observation of the different stages of cluster formation, because it provides the unique possibility to image DNA and metallic nanoparticles simultaneously. Finder grids were used to investigate exactly the same cluster chains with SFM and transmission electron microscopy, thus combining the advantages of both microscopic methods to study the process of DNA metallization. Copyright © 2002 John Wiley & Sons, Ltd.
Enrichment of Al in the topmost surface of AlN crystalline film prepared by post‐irradiation
Authors: Mizuhara Y. , Mitsuhashi R. , Nagatomi T. , Takai Y. , Inoue M. , Shimizu R.
Published: August 2002

Crystalline AlN film that was prepared by post‐irradiation under specific conditions has been examined by reflection high‐energy electron diffraction (RHEED) and ion scattering spectroscopy (ISS). The RHEED pattern clearly indicated that an AlN crystalline structure is grown on an Al substrate under irradiation of 12 keV N2+ ions impinged on the Al surface at normal incidence. However, ISS revealed that the topmost surface is not the stoichiometric composition corresponding to AlN, but is significantly Al‐rich. Copyright © 2001 John Wiley & Sons, Ltd.
A holistic approach to competence development
Authors: Sundberg Lennart
Published: August 2002

Pragmatically seeing competence as a combination of a person's knowledge, experiences and abilities, it is concluded that it is not possible to directly develop another person's competence. It is just possible to set the scene, to provide the tools and act like a catalyst. A holistic and systemic approach in six steps is designed with the ambition to handle competence development in that way. Practical experiences from applying the developed methodology in a number of SMEs show that those basic assumptions at large have been correct. A method of cooperation between a university department and a practice‐oriented consultant is also developed within the project. Copyright © 2001 John Wiley & Sons, Ltd.
Competence development and learning organizations: a critical analysis of practical guidelines and methods
Authors: Löfstedt Ulrica
Published: August 2002

In critically analysing eight research papers about competence development in organizations, it is found that systemic models, methods and approaches have a great deal to offer in the field of competence development in SMEs. However, the proposed methods and approaches are still rather tentative and theoretically based. Hence, they need to be further empirically tested and adapted to practical use. It is also desirable to further develop and elaborate all the ideas raised in the papers in order to bring them to full maturity. Finally, in order to meet all the requirements in the European Commission's ADAPT programme, further research and development is needed concerning how to combine and extend the original methods discussed in this analysis. Copyright © 2001 John Wiley & Sons, Ltd.
Multi‐modal investigation of a business process and information system redesign: a post‐implementation case study
Authors: Eriksson Darek M.
Published: August 2002

Multi‐modal systems thinking (MST) has emerged in recent years as an alternative scientific paradigm to the more established ones, founded on positivistic, hermeneutic and critical bases, respectively. Among others, MST offers a system researcher and practitioner the multi‐modal theory as an analysis and design tool. An attempt to use this is presented in this article. More specifically, a situation where an implementation of a new business process, supported by a new computerized information system, has taken place causing some unpredicted and unwanted consequences is presented. This case is analysed with the help of multi‐modal theory, leading to an identification of system design shortcomings. This exercise shows that the employed theory is a powerful tool for construction of multi‐perspective models; it provides plausible intelligibility for why unexpected consequences emerged. Further, its use generated some heuristics for future systems modelling, analysis and design. The study also shows that the theory is ambiguous in its application; this in turn calls for its further development and operationalization. Copyright © 2001 John Wiley & Sons, Ltd.
Improvement of co‐ordination: re‐scripting research for multi‐agent environments
Authors: Dash D. P.
Published: August 2002

This paper examines some of the contributions of Gerard de Zeeuw to scholarship in general and to the study of multi‐agent contexts in particular. His general contribution to scholarship revolves around the notions of research and improvement of action. In de Zeeuw's scholarly writings, research has been viewed as a developing narrative. As the practice of research expands in any field, it comes in contact with greater and greater variety of disturbances and this creates a strain on the basic script on which the narrative of research in that field is based. This can lead to a narrative break‐off. However, sometimes the script can be so modified as to restore the flow of the narrative, until another period of strain is experienced. Such a narrative break‐off is evident in the so‐called applied disciplines where researchers cannot ignore the influence of various agents while seeking to bring about improvements in a practical context. Here, the context of research becomes a multi‐agent context, where multiple viewpoints and frameworks intercede in the process of creation of various effects. The paper describes the kind of response developed in the work of de Zeeuw to deal with the task of improving co‐ordination in multi‐agent contexts. Copyright © 2002 John Wiley & Sons, Ltd.
Flowing
Authors: Kooistra Jan
Published: August 2002

‘The absence of a terminology is not a problem of the absence of truth for things that cannot be named, but the problem of the incompatibility in principle between, on the one hand, the need to order and, on the other, the result of an ordering, as this incompatibility is expressed in the procedure of particular inclusion and exclusion’. Formulated this way one could summarise the dilemma de Zeeuw was—and still is—trying to by‐pass during his scientific life. How to judge the quality of reasoning in the social sciences when you are part of the same system? Flowing was written on the occasion of the superannuation of de Zeeuw. It is showing the kind of escape from this dilemma that systems theory is offering—at least the kind of escape de Zeeuw is offering from his view of systems theory. Flowing refers to a special kind of systems. The structure of these systems is simultaneously both the means and the outcome of the social practices associated with elements of the system. Flowing is a narration—a narration about the social practice of survival. Copyright © 2002 John Wiley & Sons, Ltd.
Role of magnetic resonance imaging in the staging of gastrointestinal neoplasms
Authors: Ferraris Renato , del Piano Amalia , Galli Joseph J.
Published: August 2002

A concise review is presented of the current applications and techniques of magnetic resonance imaging (MRI) in the field of diagnostic imaging of oncologic disease of the gastrointestinal tract, with a summary of the diagnostic possibilities of MRI in the various types of tumor pathology of the gastrointestinal tract. We conclude with a review of the specific situations in which MRI presents distinct advantages over other diagnostic imaging methods (such as computed tomography and ultrasound). Semin. Surg. Oncol. 20:122–129, 2001. © 2001 Wiley‐Liss, Inc.
In vivo measures of dopaminergic radioligands in the rat brain: Equilibrium infusion studies
Authors: Kilbourn Michael R. , Sherman Phillip S. , Kuszpit Kyle
Published: August 2002

The application of an equilibrium infusion method for measuring specific in vivo radioligand binding in the conscious rat brain was evaluated for two ligands of the dopaminergic system, (+)‐α‐[11C]dihydrotetrabenazine (DTBZ) and d‐threo‐[11C]methylphenidate (MePhen). Both radioligands can be successfully utilized to reach equilibrium distributions in rat brain within 1 h; combinations of tritiated and carbon‐11‐labeled radiotracers can furthermore be used to obtain simultaneous measures of the neuronal membrane dopamine transporter (using [3H]MePhen) and vesicular monoamine transporter (using [11C]DTBZ) in the same animal. These studies provided quantitative measures of distribution volume ratios, which represent specific radioligand binding. Stereospecificity of in vivo binding was demonstrated using equilibrium infusions of the low‐affinity isomers of each ligand, (−)‐α‐[11C]dihydrotetrabenazine (DTBZ) and l‐threo‐[11C]methylphenidate, both of which produced uniform brain distributions and no specific binding. Specific binding of (+)‐α‐[11C]dihydrotetrabenazine was blocked by co‐infusion of tetrabenazine, but was unaffected by administration of methylphenidate, haloperidol, or apomorphine. Specific binding of d‐threo‐[11C]methylphenidate, conversely, was blocked with unlabeled methylphenidate but not affected by tetrabenazine or the dopamine receptor ligands. Equilibrium measures of in vivo radioligand binding, as utilized in this study, offer a quantitative means to evaluate acute and chronic drug effects on in vivo radioligand binding in the rat brain. Synapse 43:188–194, 2002. © 2002 Wiley‐Liss, Inc.
Evaluation of PET ligands (+)N‐[11C]ethyl‐3‐piperidyl benzilate and (+)N‐[11C]propyl‐3‐piperidyl benzilate for muscarinic cholinergic receptors: A PET study with microdialysis in comparison with (+)N‐[11C]methyl‐3‐piperidyl benzilate in the conscious monkey brain
Authors: Nishiyama Shingo , Tsukada Hideo , Sato Kengo , Kakiuchi Takeharu , Ohba Hiroyuki , Harada Norihiro , Takahashi Kazuhiro
Published: August 2002

We developed PET ligands (+)N‐[11C]ethyl‐3‐piperidyl benzilate ([11C](+)3‐EPB) and (+)N‐[11C]propyl‐3‐piperidyl benzilate ([11C](+)3‐PPB) for cerebral muscarinic cholinergic receptors. The distribution and kinetics of the novel ligands were evaluated for comparison with the previously reported ligand (+)N‐[11C]methyl‐3‐piperidyl benzilate ([11C](+)3‐MPB) in the monkey brain (Macaca mulatta) in the conscious state using high‐resolution positron emission tomography (PET). At 60–91 min postinjection, regional distribution patterns of these three ligands were almost identical, and were consistent with the muscarinic receptor density in the brain as previously reported in vitro. However, the time–activity curves of [11C](+)3‐EPB and [11C](+)3‐PPB showed earlier peak times of radioactivity and a faster clearance rate than [11C](+)3‐MPB in cortical regions rich in the receptors. Kinetic analysis using the three‐compartment model with time–activity curves of radioactivity in metabolite‐corrected arterial plasma as input functions revealed that labeling with longer [11C]alkyl chain length induced lower binding potential (BP = k3/k4), consistent with the rank order of affinity of these ligands obtained by an in vitro assay using rat brain slices and [3H]QNB. The cholinesterase inhibitor Aricept administered at doses of 50 and 250 μg/kg increased acetylcholine level in extracellular fluid of the frontal cortex and the binding of [11C](+)3‐PPB with the lowest affinity to the receptors was displaced by the endogenous acetylcholine induced by cholinesterase inhibition, while [11C](+)3‐MPB with the highest affinity was not significantly affected. Taken together, these observations indicate that the increase in [11C]alkyl chain length could alter the kinetic properties of conventional receptor ligands for PET by reducing the affinity to receptors, which might make it possible to assess the interaction between endogenous neurotransmitters and ligand‐receptor binding in vivo as measured by PET. Synapse 40:159–169, 2001. © 2001 Wiley‐Liss, Inc.
Effect of axial deformation on vibration of tall buildings
Authors: Swaddiwudhipong Somsak , Lee Seng‐Lip , Zhou Qin
Published: August 2002

In this paper, the governing equations of a frame‐core wall building are formulated through the continuum approach and the whole structure is idealized as a shear–flexural cantilever. The effect of axial deformation in the frame is considered and incorporated in the formulation of the governing equations. The Bubnov–Galerkin method is used to transform the governing differential equations into a set of algebraic equations. Numerical examples are solved and the results compared with the values obtained from the finite element package ‘ETABS’. The study indicates that the effect of axial deformation should be considered especially for tall and/or slender buildings. The proposed method is simple and efficient, provides reasonably accurate results and can be easily implemented on any personal computer. Copyright © 2001 John Wiley & Sons, Ltd.
Sound and faulty arguments generated by preservice biology teachers when testing hypotheses involving unobservable entities*
Authors: Lawson Anton E.
Published: August 2002

A sample of preservice biology teachers (biology majors) enrolled in a teaching methods course formulated and attempted to test six hypotheses to answer a causal question about why water rose in a jar inverted over a burning candle placed in a pan of water. The students submitted a lab report in which arguments and evidence for testing each hypothesis were presented in an if/then/therefore hypothetico‐predictive form. Analysis of written arguments revealed considerable success when students were able to manipulate observable hypothesized causes. However, when the hypothesized causes were unobservable, such that they could be only indirectly tested, performance dropped, as shown by use of three types of faulty arguments: (a) arguments that had missing or confused elements, (b) arguments whose predictions did not follow from hypotheses and planned tests, and (c) arguments that failed to consider alternative hypotheses. Science is an enterprise in which unobservable theoretical entities and processes (e.g., atoms, genes, osmosis, and photosynthesis) are often used to explain observable phenomena. Consequently, if it is assumed that effective teaching requires prior understanding, then it follows that these future teachers have yet to develop adequate hypothesis‐testing skills and sufficient awareness of the nature of science to teach science in the inquiry mode advocated by reform guidelines. © 2002 Wiley Periodicals, Inc. J Res Sci Teach 39: 237–252, 2002
Adverse effects of prenatal methimazole exposure
Authors: Di Gianantonio Elena , Schaefer Christof , Mastroiacovo Pier P. , Cournot Marie P. , Benedicenti Francesco , Reuvers Minke , Occupati Brunella , Robert Elisabeth , Bellemin Beatrice , Addis Antonio , Arnon Judy , Clementi Maurizio
Published: August 2002

Background

A specific phenotype of methimazole (MMI) induced malformations has recently been postulated. MMI embryopathy is characterized by minor dysmorphic features, choanal atresia and/or esophageal atresia, growth retardation, and developmental delay.

Methods

We prospectively studied the outcome of pregnancy in 241 women counseled by 10 Teratology Information Services (TIS) of the European Network of Teratology Information Services (ENTIS) because of MMI exposure, and compared them with those of 1,089 pregnant women referred to TIS because of exposure to nonteratogenic drugs (control group). Information was obtained by mail or telephone interview.

Results

There was no increase in the general rate of major anomalies or of spontaneous or induced abortions in the MMI‐exposed group in comparison with the control group. Two newborns were affected with one of the major malformations that are part of the postulated embryopathy.

Conclusions

The results of this study indicate that choanal as well as esophageal atresia may have a higher incidence than expected in fetuses exposed to MMI between 3 and 7 gestational weeks. Until further data are available, thyrotoxicosis should be treated with propylthiouracil, as it is apparently safer for use during the fertile period. Teratology 64:262–266, 2001. © 2001 Wiley‐Liss, Inc.
Making Sense and Making Use of Feedback from Focus Groups
Authors: Richard Tiberius
Published: August 2002

Obtaining feedback on teaching and learning from focus groups can be done efficiently and provide a wealth of information.
The toxicities of a polyunsaturated fatty acid and a microcystin to Daphnia magna
Authors: Reinikainen M. , Meriluoto J. A. O. , Spoof L. , Harada K.‐i.
Published: August 2002

Polyunsaturated fatty acids (PUFAs) are essential components of zooplankton diets. However, studies with PUFAs from cyanobacteria indicate toxic properties. We investigated the toxicity of the PUFA γ‐linolenic acid and the cyanobacterial peptide toxin microcystin‐LR to Daphnia. The PUFA was acutely toxic at a concentration of 9 μg ml−1. The effect of microcystin‐LR was not statistically significant at the concentration used (3 μg ml−1), but an additive effect with the PUFA was observed. Relative to LC50‐values of well‐known pollutants, the PUFA was intermediately toxic. The activity equaled that of microcystin‐LR, which is commonly treated as one of the most potent cyanobacterial toxins. Our results suggest that the toxic properties of PUFAs deserve more attention. © 2001 John Wiley & Sons, Inc. Environ Toxicol 16: 444–448, 2001
The Fourth Generation: New Strategies Call for New Eco‐Indicators
Authors: Simons Lucas , Slob Adriaan , Holswilder Houke , Tukker Arnold
Published: August 2002

Under pressure from public opinion, the attitude of companies toward environmental issues has changed
considerably since the 1970s. Over the past decades, there have been three distinct generations of environmental
strategies and indicators. Now, at the beginning of a new century, we can start to see the contours of the fourth
generation of environmental strategies and indicators—a generation that eventually will change the rules of
the business game. © 2001 John Wiley & Sons, Inc.
Evidence for a new structure in a mixed metal sulphate system by EXAFS
Authors: Lima R. J. C. , Sasaki J. M. , Ayala A. P. , Freire P. T. C. , Guedes I. , Melo F. E. A. , Mendes‐Filho J. , Valerio M. E. G. , Macedo Z. S. , de Lima J. F. , Mastelaro V. R.
Published: August 2002

EXAFS measurements on and above the CsLIII absorption edge were performed in LiCsSO4 (LCS) and in the system Li1.44Rb0.11Cs0.45SO4 (LRCS), aiming at the identification of the local symmetry around Cs ions in this new mixed metal sulphate LRCS. EXAFS simulations were also carried out and the results of the LRCS agrees well with recent single‐crystal x‐ray diffraction measurements, confirming that a new crystalline phase is expected for the mixed system LiCsSO4–LiRbSO4. Copyright © 2002 John Wiley & Sons, Ltd.