bluuebunny/crossref_metadata_2025 huggingface dataset:
An oral bioassay for the toxicity of hydramethylnon to individual workers and queens of Argentine ants, Linepithema humile
Authors: Hooper‐Bùi Linda M , Rust Michael K
Published: August 2002

We have developed an oral bioassay to determine the toxicity of hydramethylnon to individual workers and queens of the Argentine ant, Linepithema humile. We fed seven concentrations of hydramethylnon in suspension to individual workers or queens, determined the amount of hydramethylnon ingested and evaluated the individual ants for mortality 14 days later. At concentrations ≥0.37 g liter−1, the amount of liquid the queens ingested decreased dramatically, indicating that Argentine ant queens may detect hydramethylnon. Significantly larger volumes of the two highest concentrations of the hydramethylnon suspension were ingested by the workers, compared to the lower concentrations, suggesting that hydramethylnon may act as a feeding stimulant for the workers. Worker mortality was higher than queen mortality at the highest concentrations tested. The highest worker mortality resulted when the ants ingested 1.03 µg of hydramethylnon per mg of ant tissue. At the highest concentration (1.0 g liter−1) tested, workers ingested almost 12 times as much active ingredient per mg of body weight as did queens, suggesting that, in order to increase mortality of queens, multiple feedings must occur.

© 2001 Society of Chemical Industry
Microscopic analysis of the effect of azoxystrobin treatments on Mycosphaerella graminicola infection using green fluorescent protein (GFP)‐expressing transformants
Authors: Rohel Eric A , Cavelier Nadine , Hollomon Derek W
Published: August 2002

Green fluorescent protein (GFP)‐expressing transformants were used to investigate the effects of strobilurin fungicide azoxystrobin on Mycosphaerella graminicola infection. Azoxystrobin treatments (125 or 250 g AI ha−1) were applied at various stages of the infection process under controlled conditions. GFP transformants showed conserved in vitro sensitivity to azoxystrobin and pathogenicity. Azoxystrobin controlled over 90% of M graminicola infections when applied before or during penetration of the pathogen (15% of the incubation phase). Azoxystrobin also impaired the growth of intercellular hyphae in M graminicola post‐penetration infection stages when applied at up to 50% of the incubation phase. Incubating infections observed in treated leaves were viable, but their growth was impaired and they did not induce necrosis under controlled conditions. Reduction by half of azoxystrobin dosage had little or no effect on azoxystrobin efficiency in controlling M graminicola. The contribution of post‐penetration fungistatic effect to azoxystrobin curative properties toward M graminicola in a field situation is discussed.

© 2001 Society of Chemical Industry
Quantitative structure–transformation relationships of phenylurea herbicides
Authors: Berger Bernhard M , Müller Martin , Eing Andreas
Published: August 2002

Quantitative relationships between the structure of phenylurea herbicides and their transformation in different matrices have been developed. Experimental data on microbial transformation by pure and mixed cultures of soil micro‐organisms in inoculated and native soil, as well as on chemical transformation by hydrolysis in sterile soil and water, were available from previous studies. Around 60 experimental or calculated descriptors were used. Quantum chemical calculations were performed with three different semi‐empirical methods. Models developed with multiple linear regression were generally easier to interpret than those derived with partial least‐squares projection to latent structures. Quite simple and interpretable models could be found to predict transformation rates by pure cultures from lipophilicity, by mixed cultures from adsorption distribution coefficients, and by chemical or enzymatic hydrolysis from electronic properties. Transformation in inoculated soil could not be predicted, but for native soil the use of a quantum chemical descriptor for reactivity (energy of LUMO) together with molar refraction resulted in a general model.

© 2001 Society of Chemical Industry
An index technique to monitor broadcast calibration and bait pick up, plus rodent and avian sign under arid conditions
Authors: Sterner Ray T , Ramey Craig A
Published: August 2002

As part of product‐performance and wildlife‐hazards studies of 2% zinc phosphide (Zn3P2) steam‐rolled‐oat baits (11.2 kg ha−1) to reduce vole populations (Microtus spp) in alfalfa (Medicago sativa), we used randomly located, brushed‐dirt plots (eight ∼930−cm2 plots per 0.2‐ha enclosure) to monitor bait‐broadcast and ‐removal patterns, as well as to index vole and avian sign. Research was conducted in 18 × 0.2‐ha enclosures containing 2.5‐year‐old stands of alfalfa; a 2‐day pre‐bait (placebo baits broadcast in all enclosures) period followed by a 14‐day test‐bait period (placebo and 2% Zn3P2 baits in nine enclosures each) characterized the bait exposures. Baits were broadcast manually by two certified pesticide applicators (CPAs) using Spyker® Model‐75 spreaders. Baits that fell onto plots were counted <30 min later to assess the uniformity of bait distribution. The main statistical design was a 2 (placebo or Zn3P2 baits) × 3 (vole‐only, vole–pheasant, vole–quail exposures) × 14 (days) factorial, with days considered repeated measurements. In the six vole‐only enclosures, baits were removed from the brushed‐dirt plots and replaced with four 0% or 2% Zn3P2 baits (one per 232.6‐cm2 quadrant; 32 per enclosure); these ‘placed’ baits were then monitored daily for removal, while the surfaces of all plots were monitored daily for the presence : absence of animal/bird sign. Key results were: (a) 3.51 (±2.66) and 3.39 (±3.52) mean (±SD) baits were found on plots after pre‐bait and test‐bait broadcasts, respectively—less than the predicted 4.52 particles per 930‐cm2 plot; (b) baits ‘placed’ on plots in placebo‐baited enclosures were removed earlier than those in Zn3P2‐baited enclosures—data in agreement with observed vole mortality; and (c) species × bait interactions occurred for both the vole‐ and pheasant‐sign counts, but not quail‐sign counts—data also indirectly confirming Zn3P2‐induced mortality effects on voles and pheasants. This technique has utility for a variety of wildlife biology and chemical registration studies; although limited to arid conditions, the technique affords useful indices of broadcast calibration, bait pick‐up, as well as target and non‐target species mortality.

Published in 2002 for SCI by John Wiley & Sons, Ltd
Analysis of a hybrid plate girder bridge during erection: collapse of Tennessee Highway 69 bridge
Authors: Wojnowski Daniel A , Domel August W , Wilkinson John A , Kenner Matthew T
Published: August 2002

The state of stress and buckling stability of a bridge structure during construction must be fully understood during the erection process. The live and dead loads that act upon a structure during erection may result in instability of the partially completed structure. For this reason temporary and/or permanent bracing may be required. It is of utmost importance that engineers and contractors understand these principles. Study of the collapse of the Tennessee Highway 69 bridge gives insight into the principles of structural stability during erection. The following gives the reader an understanding of design and analysis techniques that can be used to determine the structural stability of a structure during erection. More importantly, the paper illustrates the effect of lack of stability during erection of a bridge.
Recent progress in pharmacological research of propolis
Authors: Banskota Arjun H. , Tezuka Yasuhiro , Kadota Shigetoshi
Published: August 2002

Propolis is a resinous hive product collected by honeybees from various plant sources. It is a popular folk medicine possessing a broad spectrum of biological activities. It has also been used as a health drink in various Asian, European and American countries. Several groups of researchers have focused their attention on the biological activity of propolis and its active principles. Many scientific articles are published every year in different international journals related to the pharmacological properties of propolis. This review article compiles recent findings (since 1995) on the pharmacological properties of propolis focusing on its antihepatotoxic, antitumour, antioxidative, antimicrobial and antiinflammatory properties. The possible mechanism of action of propolis as well as the active compounds are discussed. Copyright © 2001 John Wiley & Sons, Ltd.
Screening of Malian medicinal plants for antifungal, larvicidal, molluscicidal, antioxidant and radical scavenging activities
Authors: Diallo D. , Marston A. , Terreaux C. , Touré Y. , Smestad Paulsen B. , Hostettmann K.
Published: August 2002

A total of 78 different extracts from 20 medicinal plants belonging to 14 plant families from Mali were tested for their antifungal, larvicidal, molluscicidal, antioxidant and radical scavenging activities. Dichloromethane, methanol, water and ethanol extracts were used. TLC autobiography for antifungal activity was run with Cladosporium cucumerinum and Candida albicans. Extracts were also tested on the larvae of the mosquitoes Aedes aegypti, Anopheles gambiae and Culex quinquefasciatus. Molluscicidal activities were established with the snails Biomphalaria glabrata, Biomphalaria pfeifferi and Bulinus truncatus. β‐Carotene and DPPH solutions sprayed on TLC plates were used for antioxidant and radical scavenging assays. Of the extracts investigated, 20% were antioxidant and radical scavengers, 19% fungicidal, 30% were larvicidal and 11% were molluscicidal. Three of the plant extracts, from Cussonia barteri (Araliaceae), Glinus oppositifolius (Aïzoaceae) and Lannea velutina (Anacardiaceae) gave positive responses in all four tests. Copyright © 2001 John Wiley & Sons, Ltd.
Cardiovascular effects of the methanol and dichloromethanol extracts from Mentha suaveolens Ehrh.
Authors: Bello R. , Calatayud S. , Beltrán B. , Primo‐Yúfera E. , Esplugues J.
Published: August 2002

Methanol and dichloromethanol extracts of the leaves and stems of Mentha suaveolens Ehrh. have been tested for their effects on resting arterial blood pressure, heart rate and noradrenaline induced hypertension. Both extracts administered by i.v. bolus to urethane anaesthetized normotensive rats reduced the mean arterial blood pressure and heart rate, while only the dichloromethanol extract prevented the noradrenaline induced hypertension. Copyright © 2001 John Wiley & Sons, Ltd.
Induction of differentiation in rat C6 glioma cells with Saikosaponins
Authors: Tsai Yan‐Jyu , Chen I‐Ling , Horng Lin‐Yea , Wu Rong‐Tsun
Published: August 2002

The effects of saikosaponins (a, b1, b2, c, d), isolated from Bupleurum Radix, on the induction of differentiation in rat C6 glioma cells were studied. Saikosaponins a and d were shown to inhibit cell proliferation and alter cell morphology. In addition to cytostasis, the enzymatic activities of glutamine synthetase (GS) and 2′,3′‐cyclic nucleotide 3′‐phosphohydrolase (CNP) were also noticeably increased after treatment with saikosaponin a. Nevertheless, saikosaponin d only showed an increase of GS activity, no significant changes in CNP activity were found. These results suggest that saikosaponin a can induce the differentiation of C6 glioma cells into astrocytes and/or oligodendrocytes, but saikosaponin d can only induce the differentiation of C6 glioma cells into astrocytes. Copyright © 2002 John Wiley & Sons, Ltd.
Diuretic activity of Fabiana patagonica in rats
Authors: Álvarez M. E. , María A. O. M. , Saad J. R.
Published: August 2002

A pharmacological evaluation of the diuretic activity of Fabiana patagonica Speg. (Solanaceae) was carried out in isotonic saline loaded rats. The data reported in the present work indicate that the acetone extract and infusion of the aerial part of Fabiana patagonica showed a moderate diuretic activity. This activity could be due, in part, to the presence of oleanolic acid isolated as the major metabolite of F. patagonica. Copyright © 2002 John Wiley & Sons, Ltd.
The antiulcerative effect of Thai Musa species in rats
Authors: Pannangpetch Patchareewan , Vuttivirojana Auranut , Kularbkaew Churairat , Tesana Samarn , Kongyingyoes Bunkerd , Kukongviriyapan Veerapol
Published: August 2002

Bananas are reported to have an antipeptic ulcer effect, however, the beneficial action can be affected by many factors, including the variety. Our study was undertaken to investigate the antipeptic ulcer effect of the Palo and Horn varieties of banana, grown and consumed in the northeast of Thailand. Indomethacin and acetic acid‐induced gastric lesions in rats were employed as models of peptic ulcer disease. The lengths of gastric lesions in the glandular part of the stomach were measured for the assessment of the protective effect of bananas. The healing effect was studied by histological examination of the ulcerated area. The lesions in rats treated with the extract of banana were significantly less dominant than those of the control. The average length of total lesions of rats treated with an extract of Palo or Horn bananas at a dose of 1.0 g/kg/d for 3 days prior to indomethacin administration were 4.47±1.2 and 1.87±0.44 mm, respectively, whereas those observed in the control rats were 14.56±2.43 mm. In the ulcer‐healing model, only the Hom‐banana‐extract‐treated group showed a beneficial effect which manifested as a milder degree of histological change than that of the indomethacin‐induced‐chronic‐ulcer control group. However, in acetic acid‐induced ulcers, the histological changes of every group were similar. The present findings indicate that bananas of different varieties have varying antipeptic ulcer effects. The extracts of Palo and Hom bananas have a prominent gastroprotective effect, whereas only the extract of Hom banana had an observed ulcer‐healing effect. Copyright @ 2001 John Wiley & Sons, Ltd.
Effect of quercetin on tachykinin‐induced plasma extravasation in rat urinary bladder
Authors: Wille Paulo R. , Ribeiro‐do‐Valle Rosa M. , Simões Cláudia M. O. , Gabilan Nelson H. , Nicolau Mauro
Published: August 2002

The effect of quercetin on substance P‐induced plasma extravasation in rat urinary bladder and its modulation by endogenous peptidases in conscious rats was studied. Plasma protein extravasation (PE) was assayed by measurement of extravasated Evans blue dye (μg/g dry tissue). Intravenous injection of substance P (SP, 10 nmol/kg) significantly increased PE in the urinary bladder. PE evoked by SP was increased significantly by quercetin (20 mg/kg, p.o.) pretreatment in the urinary bladder (73.5 ± 4.9 to 152.2 ± 9.9). Pretreatment with captopril, an angiotensin‐converting enzyme (ACE) inhibitor (10 nmol/kg, i.v.), or with phosphoramidon, a neutral endopeptidase (NEP) inhibitor (2.5 μmol/kg, i.v.) also potentiated the SP‐induced PE in urinary bladder, 286.2 ± 20.4 and 323.3 ± 34.0, respectively. Quercetin did not show any effect on neurokinin‐A (NKA, 10 nmol/kg, i.v.) ‐induced plasma extravasation. The present study demonstrates that quercetin potentiates the PE induced by substance P in the urinary bladder. These effects suggest that this flavonoid might cause inhibition of NEP and/or ACE. Copyright © 2001 John Wiley & Sons, Ltd.
Properties of the Duane plot for repairable systems
Authors: Rigdon Steven E.
Published: August 2002

The Duane plot is a plot of cumulative operating time against the cumulative failure rate on double logarithmic axes. It is often claimed that the power law process, a non‐homogeneous Poisson process with intensity function $\lambda(t)=(\beta/\theta)(t/\theta)^{\beta-1}$, implies a linear Duane plot. We show that this implication and its converse are false. Copyright © 2002 John Wiley & Sons, Ltd.
Structure and spin‐state energetics of an iron porphyrin model: An assessment of theoretical methods
Authors: Scherlis Damián A. , Estrin Darío A.
Published: August 2002

The ability of unrestricted Hartree–Fock (UHF), Møller–Plesset (MP2), density functional theory (DFT), and hybrid density functional/Hartree–Fock methodologies to describe the structure and spin‐state energetics of iron porphyrins was assessed. In the first place, these techniques have been applied to Fe, Fe+, Fe2+, and Fe3+ for which HF calculations overestimate energy gaps, favoring stabilization of higher multiplicity states. DFT shows the opposite trend at the GGA level, with some improvement using the hybrid schemes B3LYP and half‐and‐half. We use the hybrid functionals to explore the dependence of the spin state with the iron displacement out of the porphyrin plane in the five‐coordinate system, for which a high‐spin ground state has been experimentally determined. The possibility of spin crossover, proposed in previous studies, is examined. Finally, the hybrid methodologies are applied to the computation of the oxyhemoglobin model. The B3LYP description of the electronic structure of both penta and hexa coordinate model systems is consistent with previous theoretical calculations and with experimental information of deoxy and oxy hemoglobin. © 2002 John Wiley & Sons, Inc. Int J Quantum Chem, 2002
Symplectic algorithm for use in computing the time‐independent Schrödinger equation
Authors: Liu Xue‐Shen , Su Li‐Wei , Ding Pei‐Zhu
Published: August 2002

We present an improved symplectic scheme‐shooting method (ISSSM) for solving the one‐dimensional time‐independent Schrödinger equation. This method is applied to computations of the eigenvalues and wave functions of the hydrogen molecule (H2) and a Morse potential; the method is also applied to computations of the parameters and wave functions of a soft potential. The numerical results are in good agreement with the exact ones or other numerical ones and illustrate that the ISSSM is more effective than the SSSM. Then the ISSSM is extended to solutions of the two‐dimensional time‐independent Schrödinger equation. The eigenvalues of the two‐dimensional harmonic oscillator and the two‐dimensional Henon–Heiles potential are calculated by using the ISSSM. The numerical results illustrate that our method is stable and convergent for two dimensions. © 2001 Wiley Periodicals, Inc. Int J Quantum Chem, 2001
Is there a bridging ligand in metal‐substituted zinc β‐lactamases? A spectroscopic and theoretical answer
Authors: Estiú Guillermina L. , Rasia Rodolfo M. , Cricco Julia A. , Vila Alejandro J. , Zerner Michael C.
Published: August 2002

The spectral features of Co(II)‐substituted metallo‐β‐lactamases were analyzed. Nuclear magnetic resonance (NMR) evidence is provided that shows no magnetic coupling between the two metal ions in Co(II),Co(II)‐βLII (β‐lactamase II from Bacillus cereus), suggesting that no bridging ligand connects them. Ultraviolet–visible (UV–vis) data are rationalized on the basis of semiempirical quantum chemical calculations of the intermediate neglect of differential overlap type (ZINDO/S). The binuclear active sites of the enzymes from B. cereus (βLII) and B. fragilis (CcrA) were modeled from the protein data bank (PDB) coordinates, and calculations were performed at the multireference configuration interaction level. The active site geometries of these enzymes were examined using the experimental electronic spectra as a guide. The model which best fits to the spectroscopic data lacks a bridging solvent molecule, in agreement with the NMR data. The model could also reproduce spectral changes seen in the mixed Zn(II),Co(II) adduct. The bands in the visible range are associated with ligand field transitions at the high‐affinity site, whereas the UV‐calculated features originate in ligand‐to‐metal charge transfer to the open shell Co(II) in the low‐affinity site. These results indirectly support the hypothesis that the Co(II),Co(II) derivative of CcrA is also unbridged, in contrast with the structure of the native zinc enzyme. These results indicate that the existence of a bridging ligand is not necessary for metallo‐β‐lactamase activity, and that the second zinc ion is not essential for lowering the pKa of the bound water. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem 88: 118–132, 2002
Theoretical study of p‐methacryloyl‐aminophenylarsonic acid
Authors: Hernández J. M. , Herrera Ana M. , García‐Serrano J. , Rivas‐Silva J. F.
Published: August 2002

Conformations of p‐methacryloylaminophenylarsonic acid (p‐MAPHA) are determined through molecular mechanics and DFT/B3LYP calculations. Solvation effects are studied within the self‐consistent isodensity continuum model (SCI‐PCM). The stationary points were found to correspond to minima as verified by the analysis of vibrational frequencies in the molecule. The molecular optical absorption was obtained by using different solvent environments. The present results are in good agreement with the available experimental data. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Pseudorotational dynamics of H3+ and Li3+
Authors: Hagelberg F.
Published: August 2002

The origin of the pseudoprecession phenomenon is investigated through a computational study of the time evolution of H3+ and Li3+ by electron nuclear dynamics theory. In particular, the pseudorotation of both molecules is shown to induce a spatial rotation, which in turn leads to Coriolis coupling of the two orthogonal nuclear shape deformation modes. This effect is rooted in an anisotropy of the molecular ground state potential energy surface that is caused by the interaction between the D3h ground state and a twofold degenerate first excited state. Computations are performed for a variety of vibrational energies. In addition, the impact of the anharmonicity of the ground state potential surface on the shape deformation modes and the coupling between them is discussed. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Investigation of the structural units of germanium sulfide and selenide by quantum chemical methods
Authors: Fejes István , Billes Ferenc
Published: August 2002

This article deals with the modeling of the structural units (clusters) of germanium sulfide and germanium selenide glasses by quantum chemical (ab initio Hartree–Fock) methods. Clusters of different sizes were investigated. Geometric parameters and vibrational frequencies of these structural units were calculated. The quantum chemical calculations were followed by normal coordinate analysis. Based on the yielded results, the vibrational spectra of the clusters were simulated. The results for germanium sulfide and germanium selenide were compared. It was concluded that in the spectral regions where germanium sulfide is not applicable for fiber optics, germanium selenide or different germanium sulfide–selenides are suitable to replace it. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
AIM study of pyrimidyl carbocyclic analogues of nucleosides based on cyclopentene rings
Authors: González‐Moa María J. , Terán Carmen , Mosquera Ricardo A.
Published: August 2002

A topological charge electron density analysis using the atoms in molecules (AIM) theory with HF/6‐31++G**// HF/6‐31G* wave functions was performed oncis‐pyrimidyl andcis‐5/6‐halopyrimidyl derivatives of 1,2‐disubstituted analogues of carbocyclic nucleosides. In these analogues, which belong to an important class of antiviral or antitumoral compounds, the usual ribose or deoxyribose is replaced by a carbocycle with a hydroxymethyl group and a heterocyclic base on adjacent carbons and a double bond between positions 2 and 3 of the carbocycle. The results obtained demonstrate that 5‐halogenation does not alter the relative energy sequence of the conformers and gives rise to no meaningful distortion of the electron distribution in the cyclopentene ring. In fact, the difference in the total electron population of this cycle between the parent and any of the halogenated molecules is never larger than 7×10−3a.u. It has been found that the electron population of the αCatom in the chloro derivatives is enlarged with respect to the unhalogenated species. The 5‐halogenation results in a destabilization of the C4, C5, and C6 atoms of the heterocyclic base. According to the AIM computed energy properties this destabilization originates from larger interelectronic repulsions in the C5 basin that are consistent with its reduced volume and its lower first moment of the electron density. On the other hand, 6‐halogenation produces a significant modification of the conformational equilibrium, modifying the relative energy sequence of conformers. The electronic properties are also significantly modified by 6‐halogenation. The charge transfer from the cyclopentene ring to the base reaches 0.71 a.u. in the 6‐fluoro derivative and 0.69 a.u. in the 6‐chloro derivative. © 2002 John Wiley & Sons, Inc. Int J Quantum Chem 86: 67–78, 2002
Perturbation of the intramolecular hydrogen bonds of glucose by Cu+association
Authors: Boutreau Laurence , Tortajada Jeanine , Luna Alberto , Alcamí Manuel , Mó Otilia , Yáñez Manuel
Published: August 2002

A density functional theory study of glucose and glucose–Cu+complexes has been performed to investigate the changes undergone by the set of intramolecular hydrogen bonds of the neutral system upon Cu+association. The geometries of the different species investigated were optimized at the B3LYP/6‐31G(d,p) level. The same level of theory was used to obtain the harmonic vibrational frequencies and to analyze the electron charge density by means of the atoms in molecules theory. We have shown that the interaction with Cu+strongly perturbs the set of intramolecular hydrogen bonds of the neutral. Some of these changes are a direct consequence of the conformational changes induced by the metal, which result in the breaking of some of the existing bonds or in the formation of new ones. The most important point, however, is that the intramolecular hydrogen bonds that remain are perturbed to a different extent. In general, all hydrogen bonds in which the OH donor interacts directly with the metal cation are significantly stabilized while the remaining ones become weaker. These changes influence the relative stability of the complexes as well as its capacity to interact with other systems. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Method/basis set dependence of the traceless quadrupole moment calculation for N2, CO2, SO2, HCl, CO, NH3, PH3, HF, and H2O
Authors: Höfinger Siegfried , Wendland Martin
Published: August 2002

Dipole moments and traceless quadrupole moments for a training set of nine molecules—N2, CO2, SO2, HCl, CO, NH3, PH3, HF, and H2O—were deduced from the final optimized density matrices of a series of ab initio calculations, thereby employing different levels of theory with varying basis set quality. All the results were obtained in a true ab initio sense, meaning that at a certain combination of method/basis set, the configurations of the molecules were first subjected to a geometry optimization and only afterwards the dipole and traceless quadrupole moments were derived for the final relaxed structures. All results could be compared to experimental data, thus the quality of the different models with respect to applicability and reliability of calculating molecular moments without any knowledge of structural details of the equilibrium geometries could be evaluated. Generally, a combination of methods that take into account correlation effects, together with a high‐level basis set, was found to yield molecular moments close to the experimental values. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Optimisation of the quantitative determination of chlormequat by matrix‐assisted laser desorption/ionisation mass spectrometry
Authors: Horak Jeannie , Werther Wolfgang , Schmid Erich R.
Published: August 2002

The plant growth regulator chlormequat, an involatile quaternary ammonium salt, has been quantified by matrix‐assisted laser desorption/ionisation time‐of‐flight mass spectrometry (MALDI‐TOFMS). Restrictions for quantitative MALDI‐TOFMS analysis, such as irreproducible crystallisation and unsatisfactory laser stability, have been overcome by the application of two synthesised isotopically labelled standards and the optimisation of the measurement protocol. Data acquisition at constant laser power was compared to data acquisition at approximately constant ion abundance of the relevant ions (analyte and internal standards). Data acquisition at constant ion abundance performed better and enabled a high number of consecutive firings to the same sample deposition area. Furthermore an increased sample‐to‐sample repeatability and a high reproducibility over several weeks without re‐calibration have been attained by this method. Linearity over three orders of magnitude (0.05 to 30 ng/µL chlormequat), with a correlation coefficient of 0.9997, was achieved using [13C3]‐chlormequat as internal standard. Limit of detection and limit of determination were determined to be in the low pg/µL range for pure standard solutions. Thin‐layer chromatography was applied for the removal of high amounts of choline, which is often present in plant tissue extracts and can adversely affect the ionisation and detection of chlormequat by MALDI‐TOFMS. The use of two internal standards ([13C3]‐ and [2H9]‐chlormequat) enabled direct quantification and simultaneous control of the recovery. Copyright © 2001 John Wiley & Sons, Ltd.
A study of the electrospray ionisation and ion‐trap fragmentation of [M − H]− ions of new 3,5‐disubstituted tetrahydro‐2H‐1,3,5‐thiadiazin‐2‐thiones
Authors: Martínez‐Alvarez Roberto , Martín Nazario , Seoane Carlos , Suárez Margarita , Pérez Rolando , Rodríguez Hortensia , Kayali Nour
Published: August 2002

The electrospray ionisation (ESI) in negative mode of the pharmacologically significant 3,5‐disubstituted tetrahydro‐2H‐1,3,5‐thiadiazin‐2‐thiones, and their subsequent fragmentations using an ion‐trap mass spectrometer, have been investigated. Experiments on sequential product ion fragmentations (MSn) were performed in order to elucidate the degradation pathways for these compounds. The data presented show that the fragmentation of the even‐electron [M − H]− ions could proceed through an internal nucleophilic substitution displacement. Decarboxylation and extrusion of carbon disulfide are other fragmentations observed. Copyright © 2001 John Wiley & Sons, Ltd.
Using septum‐capped vials with continuous‐flow isotope ratio mass spectrometric analysis of atmospheric CO2 for Keeling plot applications
Authors: Tu Kevin P. , Brooks Paul D. , Dawson Todd E.
Published: August 2002

Recent advances in continuous‐flow isotope ratio mass spectrometry have made possible automated analysis of δ13C and δ18O in CO2 in air from 10‐mL septum‐capped vials. With the potential to collect, transport, and analyze a large number of air samples using these small inexpensive vials, the opportunity exists for routine and statistically robust sampling of CO2 for Keeling plot applications.

With the above‐mentioned objectives in mind, we measured the precision of carbon and oxygen stable isotope ratios in the CO2 of air within septum‐capped vials using a Finnigan MAT Deltaplus XL continuous‐flow isotope ratio mass spectrometer (CF‐IRMS) interfaced to a GasBench II. The standard deviation of 45 δ13CPDB and δ18OVSMOW measurements from five vials filled with identical tank air was 0.08‰ and 0.14‰, respectively. This translated into a measurement precision (standard error; SE) of 0.01‰ δ13CPDB and 0.02‰ δ18OVSMOW. This precision was similar to that obtained with the tank air introduced directly into the GasBench II by bypassing the vials/autosampler (also with a SE = 0.01‰ for both δ13CPDB and δ18OVSMOW), suggesting minimal vial‐related effects with no storage time at ambient pressure and CO2 concentration. Further, puncturing the butyl rubber septa during filling just prior to analysis did not affect the precision (SE = 0.01‰ for both δ13CPDB and δ18OVSMOW, n = 45).

After nine days of storage in vials with unpunctured septa, neither δ13CPDB nor δ18OVSMOW changed significantly, although the precision decreased to ∼0.04‰ for both δ13CPDB and δ18OVSMOW. A greater decrease in precision was observed for vials with punctured septa (from 0.01‰ to 0.10‰ SE for both δ13CPDB and δ18OVSMOW). Further, whereas vials with punctured septa showed no change in δ18OVSMOW, δ13CPDB decreased by 0.07‰/day (r2 = 0.96). In practice, such storage‐related effects could be accounted for based on concurrent changes in reference standards.

These results suggest that air may be collected and stored in 10‐mL septum‐capped vials and analyzed in an automated fashion with the Gas Bench II/Deltaplus with sufficient precision for Keeling plot applications. Further, a relatively high sample throughput of about 4 vials per hour or about 100 vials or 2000 injections per day offers the potential for high precision with large sample sizes. Higher throughput should permit experimental advances that were not possible before. Copyright © 2001 John Wiley & Sons, Ltd.
Isoelectric focusing nonporous silica reversed‐phase high‐performance liquid chromatography/electrospray ionization time‐of‐flight mass spectrometry: a three‐dimensional liquid‐phase protein separation method as applied to the human erythroleukemia cell‐line
Authors: Wall Daniel B. , Kachman Maureen T. , Gong Siyuan S. , Parus Stephen J. , Long Michael W. , Lubman David M.
Published: August 2002

A liquid‐phase three‐dimensional protein separation method has been developed that is used to separate the cytosolic fraction of a HEL cell lysate via isoelectric focusing (IEF), nonporous silica (NPS) reversed‐phase high‐performance liquid chromatography (RP‐HPLC) and electrospray ionization time‐of‐flight mass spectrometry (ESI‐TOFMS), respectively. Several hundred unique protein molecular weights were observed in a pI range from 4.8 to 8.5 and a mass range from 5 to 85 kDa. Proteins were positively identified by analysis of the pI (±0.5 pI units), an intact protein molecular weight (±150 ppm), and peptide mass mapping results. Using the molecular weight (MW) and peptide mapping results of identified proteins it was possible to characterize their posttranslational (PTMs) and/or sequence modifications. PTMs were detected on both forms of cytosolic actin, heat shock 90 β, HINT and α‐enolase. Sequence modifications or conflicts were observed for β‐and γ‐actin, ATP β‐synthase and heat shock 90 β. IEF‐NPS‐RP‐HPLC/ESI‐TOFMS was used to determine experimental pI, MW and relative hydrophobicity values for each protein detected. This data was used to generate a 2‐D pI‐MS protein map, where proteins are displayed according to their pI and molecular weight. Protein molecular weight peaks are represented as bands in the 2‐D pI‐MS image where the gray scale of each band is proportional to the intensity of the protein molecular weight peak. In addition, a third hydrophobicity dimension (%B) was added as the % acetonitrile elution to generate a 3‐D pI‐MS‐%B plot where each protein can be tagged according to three parameters. Copyright © 2001 John Wiley & Sons, Ltd.
Investigation of reduction of Cu(II) complexes in positive‐ion mode electrospray mass spectrometry
Authors: Gianelli Luca , Amendola Valeria , Fabbrizzi Luigi , Pallavicini Piersandro , Mellerio Giorgio G.
Published: August 2002

The electrospray ionization mass spectrometry (ESI‐MS) behavior of seven Cu(II) complexes with tetradentate ligands has been studied. An unexpected reduction process, in positive ion mode, of the Cu oxidation state was observed, and shown to be due to charge transfer between the metal complex and the solvent molecules in the gas phase. Ion trap collision‐induced dissociation experiments and deuterated solvents were used to support the proposed mechanism that is not a common electrochemical redox reaction at the ESI tip, but a gas‐phase process. A series of solvents (acetonitrile, methanol, ethanol, propanol and iso‐butanol) were tested, and a correlation between ionization energy (IE) and the amount of Cu(I) produced in ESI has been demonstrated for the alcohols, although some other solvent properties should also be taken into account. The electrochemical reduction potential of the complexes in solution is also an important parameter, since complexes more easily reduced in solution are also easier to reduce in the gas phase. Copyright © 2001 John Wiley & Sons, Ltd.
Determination of azaspiracids in shellfish using liquid chromatography/tandem electrospray mass spectrometry
Authors: Furey Ambrose , Braña‐Magdalena Ana , Lehane Mary , Moroney Cian , James Kevin J. , Satake Masayuki , Yasumoto Takeshi
Published: August 2002

Azaspiracid (AZA1), a recently discovered marine toxin, is responsible for the new human toxic syndrome, azaspiracid poisoning (AZP), which is caused by the consumption of contaminated shellfish. A new, sensitive liquid chromatography/mass spectrometry (LC/MS) method has been developed for the determination of AZA1 and its analogues, 8‐methylazaspiracid (AZA2) and 22‐demethylazaspiracid (AZA3). Separation of these toxins was achieved using reversed‐phase LC and coupled, via an electrospray ionisation (ESI) source, to an ion‐trap mass spectrometer. Spectra showed the protonated molecules, [M + H]+, and their major product ions, due to the sequential loss of two water molecules, [M + H − H2O]+, [M + H − 2H2O]+, in addition to fragment ions that are characteristic of these cyclic polyethers. A highly specific and sensitive LC/MS3 analytical method was developed and, using shellfish extracts containing AZA1, the detection limit (S/N = 3) was 4 pg on‐column, corresponding to 0.8 ng/mL. Using the protocol presented here, this is equivalent to 0.37 ng/g shellfish tissue and good linear calibrations were obtained for AZA1 in shellfish extracts (average r2 = 0.9988). Good reproducibility was achieved with % RSD values (N = 5) ranging from 1.5% (0.75 µg/mL) to 4.2% (0.05 µg/mL). An efficient procedure for the extraction of toxins from shellfish aided the development of a rapid protocol for the determination of the three predominant azaspiracids. Copyright © 2002 John Wiley & Sons, Ltd.
2H‐ and 13C‐Labelled tracers compared for kinetic studies of ascorbic acid metabolism in man: a factor analytical approach
Authors: Bluck Leslie J. C. , Jones Kerry S. , Bates Christopher J.
Published: August 2002

A recent report that a 13C stable isotope method can be used to measure the kinetics of ascorbic acid uptake and distribution in man has raised some interesting questions with regard to the physiological interpretation of the data obtained, in particular the sizes of the ascorbate distribution spaces. In order to prove that this result is not a function of the label used we have compared the behaviour of two different tracers to see if they are likely to give comparable results for the kinetic parameters. Volunteers received an oral dose of ascorbic acid, half of which was labelled with 2H, and half of which was labelled with 13C. Blood samples were taken over the course of the next 48 h, and ascorbic acid mass spectra measured by gas chromatography/mass spectrometry (GC/MS). Principal component analysis was used to investigate the number of factors required to explain the total variations observed in the ratios of the molecular isotopomer cluster over the time course of the experiment. Theoretical cracking patterns were then used as test vectors in target transformation and as the basis for subsequent combination to determine tracer/tracee ratios.

Two factors were found sufficient to account for the observed cracking pattern variations within experimental error. These were identified as (1) the spectrum of unlabelled (endogenous) ascorbic acid, and (2) a linear combination of the spectra of the two labelled species used. The absence of a third factor in the decomposition indicates that there is no difference in the behaviour of the 13C‐ and 2H‐labelled tracers. Target testing allowed the tracer/tracee ratios to be determined using calculated cracking patterns, and produced equivalent results to conventional methods. Our experience in this work indicates that factor analysis has a useful place in many kinetic studies of this kind, either with one or many labelled species. Copyright © 2002 John Wiley & Sons, Ltd.
A stochastic analysis of robust estimation algorithms in H∞ with rational basis functions
Authors: Akçay Hüseyin
Published: August 2002

In this paper, a two‐stage nonlinear identification algorithm parameterized in terms of rational basis functions with fixed basis poles is studied when disturbances are subject to mild stochastic assumptions. The two‐stage algorithm is the archetype for robust estimation algorithms in H∞ and its first stage is linear‐in‐data. Conditions for the consistency of both the stages are derived. It is shown that the two‐stage algorithm enjoys a better stochastic as well as deterministic performance than those of the linear algorithms. Copyright © 2001 John Wiley & Sons, Ltd.
Active suspension for single wheel station of off‐road track vehicle
Authors: Liberzon A. , Rubinstein D. , Gutman P. O.
Published: August 2002

The main objective of ground vehicle suspension systems is to isolate a vehicle body (sprung mass) from road irregularities in order to maximize passenger ride comfort, control the attitude of the vehicle on the road, and retain continuous road–wheel contact in order to provide vehicle holding quality. An appropriate active suspension design must resolve the inherent tradeoffs between ride comfort, road holding quality, and suspension travel. In this study, a robust controller for the active suspension of an off‐road, high‐mobility tracked vehicle is designed, for the first time, using quantitative feedback theory (QFT). A simulation model of a single suspension unit of the M‐113 armored personnel carrier vehicle was used to achieve a proper active suspension design. Two measured states of the 3‐degrees‐of‐freedom mathematical model were used as feedback signals in a cascaded SISO control system. The nonlinear dynamics of the tracked vehicle suspension unit was represented as a set of linear time invariant (LTI) transfer functions, which were identified with the Fourier integral method. Computer simulations of the vehicle with passive and active suspension systems over different terrain profiles are provided. A significant reduction of the vertical accelerations induced to the sprung mass (e.g., ride comfort improvement) was achieved while keeping the road‐arm between suspension travel limits (e.g., handling quality). Copyright © 2001 John Wiley & Sons, Ltd.
Parallel collision detection between moving robots for practical motion planning
Authors: Pérez‐Francisco Miguel , Del Pobil Angel P. , Martínez‐Salvador Begoña
Published: August 2002

Motion planning has made few inroads into practical applications in the real world. Practical motion planning involving multiple moving objects with complex geometries requires very fast collision detection. We present an approach to collision detection between moving robots for motion planning. It is based on a spherical hierarchy of detail for nonconvex and curved objects that need not be partitioned into convex ones. We present results that show the stability of the approach regarding the number of polygons used to model the scene. Numerical evidence of the algorithm's efficiency is also shown by several experiments, in which we obtain average intersection detection times of around 1 ms using eight processors for two closely moving robots involving 1900 polygons. © 2001 John Wiley & Sons, Inc.
Random lifts of graphs: Independence and chromatic number
Authors: Amit Alon , Linial Nathan , Matoušek Jiří
Published: August 2002

For a graph G, a random n‐lift of G has the vertex set V(G)×[n] and for each edge [u, v] ∈ E(G), there is a random matching between {u}×[n] and {v}×[n]. We present bounds on the chromatic number and on the independence number of typical random lifts, with G fixed and n→∞. For the independence number, upper and lower bounds are obtained as solutions to certain optimization problems on the base graph. For a base graph G with chromatic number χ and fractional chromatic number χf, we show that the chromatic number of typical lifts is bounded from below by const ⋅ \documentclass{article}\pagestyle{empty}\begin{document}$\sqrt{\chi/\log\chi}$ and also by const ⋅ χf/log2χf (trivially, it is bounded by χ from above). We have examples of graphs where the chromatic number of the lift equals χ almost surely, and others where it is a.s. O(χ/logχ). Many interesting problems remain open. © 2002 John Wiley & Sons, Inc. Random Struct. Alg., 20, 1–22, 2002
Shell, Nigeria and the Ogoni. A study in unsustainable development: III. Analysis and implications of Royal Dutch/Shell group strategy
Authors: Wheeler David , Rechtman René , Fabig Heike , Boele Richard
Published: August 2002

In the first two papers of this trilogy we explored the history of the Royal Dutch/Shell group both internationally and locally in Nigeria. We described a catastrophic failure in relations with the Ogoni and the consequent fall‐out with NGOs and opinion formers more globally. In response to these events Shell embarked on a revision of its business principles and initiated a multi‐million dollar exercise in stakeholder outreach and communication. We also explored the limitations of a purely instrumental approach to ‘stakeholder management’ in Nigeria and suggested that a rights‐based approach might provide a more useful framework for managing relationships and achieving reconciliation between Shell and the Ogoni. In this third paper of the trilogy we explore Shell's current approach to strategy formulation and implementation in the context of what this means for Shell's ability to pursue the ideal of sustainable development. We apply two models for testing the level of integration of business strategy with sustainability and we observe that, whilst Shell's business principles and corporate strategy now embrace notions of market sensitivity and internal and external accountability to an unprecedented degree, the company has yet to maximize opportunities arising from its approach to sustainability and stakeholder responsiveness at the business unit level in Nigeria. Copyright © 2001 John Wiley & Sons, Ltd. and ERP Environment
Tailored colloidal AFM probes and their TEM investigation
Authors: Hüttl Grit , Klemm Volker , Popp Roswitha , Simon Frank , Müller Eberhard
Published: August 2002

The use of an individual particle attached to the end of a cantilever is the established method for characterizing colloidal interaction forces using an atomic force microscope. In this manner the geometry of the probe is well defined but the difficult handling of particles with diameters <1µm and the restricted availability of different materials as ideal spheres of the desired size and low roughness limit the variability of this method.

We propose a method to adjust the tip radius of commercial silicon tips from ∼30 nm up to 2 µm by an oxidation procedure. The resulting silica tips have ideal (hemi‐)spherical geometry and very low roughness. It is possible to vary the surface composition and properties by combining the oxidation procedure with a coating or chemical modification process.

A home‐made transmission electron microscopy holder make it possible to analyse easily and very precisely the tip radius and the thickness of layers of different materials without destruction of the system cantilever chip. This means that the probe can be analysed before and after an atomic force microscopy measurement. Copyright © 2002 John Wiley & Sons, Ltd.