bluuebunny/crossref_metadata_2025 huggingface dataset:
Ethyl cellulose polymer microspheres for controlled release of norfluazon
Authors: Pérez‐Martínez Jose I , Morillo Esmeralda , Maqueda Celia , Ginés Juan M
Published: August 2002

The pesticide norfluazon has been microencapsulated using ethyl cellulose to develop controlled‐release formulations that decrease its mobility through the soil and protect it from photodegradation. Ethyl cellulose microspheres loaded with norfluazon were prepared by the solvent‐evaporation method. To obtain the microspheres, certain conditions (pesticide/polymer ratio, percentage of emulsifying agent and solvent) were varied. The shape and size of the microspheres obtained were studied by scanning electron microscopy. Other parameters, such as solids recovery, encapsulation efficiency and pesticide loading, were also studied. The release rate of norfluazon from the different microspheres was slower than that of pure norfluazon. In particular, microspheres obtained with o‐xylene, which provided the largest diameter, retarded the initial release of the pesticide relative to microspheres obtained with chloroform, or to pure norfluazon. Moreover, the studies showed that the pesticide/polymer ratio controlled the release of norfluazon, which was slower when this ratio was low. Release rates conformed to a generalised kinetic equation for a diffusion‐controlled release mechanism, and the time taken for 50% of the active ingredient to be released into water, t50, was calculated.

© 2001 Society of Chemical Industry
Chemistry and biology of thiamethoxam: a second generation neonicotinoid
Authors: Maienfisch Peter , Angst Max , Brandl Franz , Fischer Willi , Hofer Dieter , Kayser Hartmut , Kobel Werner , Rindlisbacher Alfred , Senn Robert , Steinemann Adrian , Widmer Hansjürg
Published: August 2002

Thiamethoxam is the first commercial neonicotinoid insecticide from the thianicotinyl subclass. It was discovered in the course of our optimisation program on neonicotinoids started in 1985. Novel variations of the nitroimino‐heterocycle of imidacloprid led to 4‐nitroimino‐1,3,5‐oxadiazinanes exhibiting high insecticidal activity. Among these, thiamethoxam (CGA 293433) was identified as the best compound and selected for worldwide development. The compound can be synthesised in only a few steps and high yield from easily accessible starting materials. Thiamethoxam acts by binding to nicotinic acetylcholine receptors. It exhibits exceptional systemic characteristics and provides excellent control of a broad range of commercially important pests, such as aphids, jassids, whiteflies, thrips, rice hoppers, Colorado potato beetle, flea beetles and wireworms, as well as some lepidopteran species. In addition, a strong preventative effect on some virus transmissions has been demonstrated. Thiamethoxam is developed both for foliar/soil applications and as a seed treatment for use in most agricultural crops all over the world. Low use rates, flexible application methods, excellent efficacy, long‐lasting residual activity and favourable safety profile make this new insecticide well‐suited for modern integrated pest management programmes in many cropping systems.

© 2001 Society of Chemical Industry
Sex‐related response to organophosphorus and carbamate insecticides in adult Oriental fruit moth, Grapholita molesta
Authors: Shearer Peter W , Usmani Khawja A
Published: August 2002

During the development of a resistance‐monitoring bioassay that uses males as the life‐stage tested, the relationship of adult female and male susceptibility of Grapholita molesta to different classes of insecticides was investigated. Preliminary results indicated that more males survived diagnostic doses of azinphos‐methyl than females. Additional research revealed that, although the body mass of adult male G molesta was only 69% of that of female moths (5.67 and 8.20 mg, respectively), their LC50 values were 2.6, 4.1 and 10.3 times higher than those of females for azinphos‐methyl, malathion and parathion‐methyl, respectively. However, female G molesta moths were more tolerant to methomyl than were male moths. There was no indication that this sex‐related response occurred in G molesta larvae. The results presented here raise concerns regarding the use of pheromone traps for determining whether insecticide treatments are required and as part of resistance monitoring programs.

© 2001 Society of Chemical Industry
A field tracer study of attenuation of atrazine, hexazinone and procymidone in a pumice sand aquifer
Authors: Pang Liping , Close Murray E
Published: August 2002

A field tracer experiment, simulating point source contamination, was conducted to investigate attenuation and transport of atrazine, hexazinone and procymidone in a volcanic pumice sand aquifer. Preliminary laboratory incubation tests were also carried out to determine degradation rates. Field transport of the pesticides was observed to be significant under non‐equilibrium conditions. Therefore, a two‐region/two‐site non‐equilibrium transport model, N3DADE, was used for analysis of the field data. A lump reduction rate constant was used in this paper to encompass all the irreversible reduction processes (eg degradation, irreversible adsorption, complexation and filtration for the pesticides adsorbed into particles and colloids) which are assumed to follow a first‐order rate law. Results from the field experiment suggest that (a) hexazinone was the most mobile (retardation factor R  = 1.4) and underwent least mass reduction; (b) procymidone was the least mobile (R  = 9.26) and underwent the greatest mass reduction; (c) the mobility of atrazine (R  = 4.45) was similar to that of rhodamine WT (R  = 4.10). Hence, rhodamine WT can be used to delimit the appearance of atrazine in pumice sand groundwater. Results from the incubation tests suggest that (a) hexazinone was degraded only in the mixture of groundwater and aquifer material (degradation rate constant = 4.36 × 10−3 day−1); (b) procymidone was degraded not only in the mixture of groundwater and aquifer material (rate constant = 1.12 × 10−2 day−1) but also in the groundwater alone (rate constant = 2.79 × 10−2 day−1); (c) atrazine was not degraded over 57 days incubation in either the mixture of aquifer material and groundwater or the groundwater alone. Degradation rates measured in the batch tests were much lower than the total reduction rates. This suggests that not only degradation but also other irreversible processes are important in attenuating pesticides under field conditions. Hence, the use of laboratory‐determined degradation rates could underestimate reduction of pesticides in field conditions.

© 2001 Society of Chemical Industry
Effect of surface material on electrostatic charging of houseflies (Musca domestica L)
Authors: McGonigle Daniel F , Jackson Chris W
Published: August 2002

Houseflies (Musca domestica L) accumulated electrostatic charges when walking over clean, uncharged dielectric surfaces. The charges elicited on a walking housefly by a range of materials were quantified, allowing a triboelectric series to be determined relative to M domestica. This ranged from surfaces that charged individuals positively, eg Correx (corrugated polypropylene) [+54.1 (±4.2)pC], to those that applied a negative charge, eg clear cast acrylic [−14.9 (±2.9)pC]. Maximum positive and negative charges accumulated by individual M domestica were +73 and −27 pC. Replicate measurements on the same fly and surface showed little variation. Variation between individuals was not related to sex and was not consistent between surfaces. Different materials charged M domestica significantly differently and individual flies had significantly different charging properties. Variation in temperature between 21.3 °C and 24.7 °C and humidity between 24% and 41% RH significantly affected charge accumulated by M domestica on some surfaces, although further experimentation is needed to confirm this. The implications of this work are discussed in relation to insect trap design and pollination biology.

© 2002 Society of Chemical Industry
The effects of charge and lipophilicity on the antibacterial activity of undecapeptides derived from bovine lactoferricin
Authors: Strøm Morten B. , Rekdal Øystein , Svendsen John S.
Published: August 2002

We have investigated the effects of charge and lipophilicity on the antibacterial activity of an undecapeptide (FKCRRWQWRMK) derived from the sequence of bovine lactoferricin. We prepared ten analogues that were modified by the incorporation of Ala, Tyr, Trp, Met and Arg residues, which are amino acids known to be important for the antibacterial activity of longer derivatives of lactoferricins. All undecapeptides contained the native Trp residues in positions 6 and 8, and the Arg residues in positions 5 and 9. Generally, the Gram‐positive bacterium Staphylococcus aureus was more susceptible to these undecapeptides than the Gram‐negative bacteria, and a higher antibacterial activity was observed against Escherichia coli than against Pseudomonas aeruginosa. The only exception was the peptide Undeca 9 (RRWYRWAWRMR‐NH2), which was almost equally active against all three test strains, displaying minimal inhibitory concentrations of 10 µg/ml (5.8 µM), 7.5 µg/ml (4.4 µM) and 5 µg/ml (2.9 µM) against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus, respectively. The peptides Undeca 6 (YRAWRWAWRWR‐NH2) and Undeca 7 (YRMWRWAWRWR‐NH2) were the two most active undecapeptides against Staphylococcus aureus, both displaying a minimal inhibitory concentration of 2.5 µg/ml (1.5 µM). The study showed that a level was reached in which undecapeptides having a net charge above +4 and containing three or four Trp residues all displayed a high antibacterial activity. All undecapeptides prepared were essentially non‐haemolytic, but undecapeptides containing more than three Trp residues displayed 50% haemolysis of human red blood cells at concentrations above 400 µg/ml (>230 µM). Copyright © 2002 European Peptide Society and John Wiley & Sons, Ltd.
Antiinflammatory activity of the antirheumatic herbal drug, gravel root (Eupatorium purpureum): further biological activities and constituents
Authors: Habtemariam Solomon
Published: August 2002

Previous reports from this laboratory revealed that cistifolin from the antirheumatic herbal drug, gravel root (rhizome of Eupatorium purpureum), showed activity both in in vitro and in vivo models of inflammation. Data are now presented to show that, in addition to the LFA‐1 and other integrin‐mediated leucocyte adhesions, cistifolin inhibits the Mac‐1 (CD11b/CD18)‐dependent monocyte adhesion to fibrinogen in a concentration‐dependent manner. Further phytochemical analysis of the crude extract also led to the isolation of three known benzofurans, euparin, euparone, 6‐hydroxy‐3β‐methoxytrematone and a new benzofuran, 5‐acetyl‐6‐hydroxy‐2‐(1‐oxo‐2‐acetoxy‐ethyl)‐benzofuran. None of these compounds were active in suppressing integrin‐mediated monocytic U937 cell adhesions in vitro. Copyright © 2001 John Wiley & Sons, Ltd.
Efficacy and tolerance of Harpagophytum extract LI 174 in patients with chronic non‐radicular back pain
Authors: Laudahn Dirk , Walper Andreas
Published: August 2002

The aim of this open, multicentre study was to evaluate the clinical effectiveness and tolerance of the Devil's Claw extract LI 174 in patients suffering from non‐radicular back pain over a period of at least 6 months. A total of 130 patients were treated twice a day with tablets containing 480 mg LI 174. The treatment lasted for 8 weeks. The effectiveness was judged according to the Multidimensional Pain Scale (MPS), Arhus back pain index and to parameters evaluating the mobility of the lumbar spine (finger–floor distance, Schober's sign). Data from 117 patients were evaluated for efficacy. The results showed a significant improvement of pain symptoms and mobility of the affected sections of the patient's spine in the course of treatment. No serious side effects were observed. In view of the excellent compliance and tolerability the investigated extract appears to be an effective plant alternative for the treatment of chronic back pain. However, further studies will be needed to clarify the therapeutic value of this plant remedy. Copyright © 2001 John Wiley & Sons, Ltd.
Influence of Active Packaging on the Shelf‐life­ of Minimally Processed Fish Products in a Modified Atmosphere
Authors: Franzetti Laura , Martinoli Stefano , Piergiovanni Luciano , Galli Antonietta
Published: August 2002

The effectiveness of an innovative foam plastic tray, provided with absorbers for volatile amines and liquids, on the shelf‐life of different fish products packed under a modified atmosphere (40%CO2:60%N2), was evaluated in comparison with a standard tray. Fillets of sole (Solea solea), steaks of cod (Merluccius merluccius) and whole cuttlefish (Sepia fillouxi), placed in the two different kinds of trays, were kept at 3°C. Microbiological (TBC‐, Gram‐negative‐, H2S‐producing bacteria and lactic acid bacteria) and chemical (surface pH, TMA headspace) analyses were carried out after 3, 7 and 10 days of storage. The new packaging, associated with a rigorous control of storage temperature, increased the shelf‐life up to 10 days. In fact, the innovative tray sequestrated the greater part of trimethylamine from the headspace and led to delayed microbial growth, especially of Gram‐negative and H2S‐producing bacteria, and in addition it favoured the growth of bacterial strains such as Moraxella phenylpiruvica, which are not involved in off‐flavouring production (especially H2S), because of their lypolitic activity. Copyright © 2001 John Wiley & Sons, Ltd.
A CCC‐r chart for high‐yield processes
Authors: Ohta Hiroshi , Kusukawa Etsuko , Rahim Abdur
Published: August 2002

The cumulative count of a conforming (CCC) chart is used to monitor high‐quality processes and is based on the number of items inspected until observing r non‐conforming ones. This charting technique is known as a CCC‐r chart. The function of the CCC‐r chart is the sensitive detection of an upward shift in the fraction defectives of the process, p. As r gets larger, the CCC‐r chart becomes more sensitive to small changes of upward shift in p. However, since many observations are required to obtain a plotting point on the chart, the cost is fairly high. For this trade‐off problem it is necessary to determine the optimal number of non‐conforming items observed before a point is plotted, the sampling (inspection) interval, and the lower control limit for the chart. In this paper a simplified optimal design method is proposed. For illustrative purposes, some numerical results for the optimal design parameter values are provided. The expected profits per cycle obtained using the proposed optimal design method are compared with those obtained using other misspecified parameter values. The effects of changing these parameters on the profit function are shown graphically. Copyright © 2001 John Wiley & Sons, Ltd.
Efficient method to perform CAP/CI calculations for temporary anions
Authors: Sommerfeld Thomas , Santra Robin
Published: August 2002

Electronically metastable states can efficiently be investigted using ℒ︁2 techniques, such as the complex absorbing potential (CAP) or the stabilization method; but, the study of autodetaching systems is nonetheless far more expensive than the investigation of comparable bound states. The costly step of the ℒ︁2 methods for resonances involves the repeated diagonalization of a parameterized Hamilton operator, and in this communication we investigate representations of the needed operators in very small basis set consisting of a few eigenstates of the physical Hamiltonian. It is shown that CAP calculations can indeed be performed using a very small eigenstate basis set, whereas basis sets of comparable size are unsuitable for stabilization calculations. Our results allow us to study the frequently employed energy selection procedure in the context of Siegert energies. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 82: 218–226, 2001
The hydration of the uranyl dication: Incorporation of solvent effects in parallel density functional calculations with the program PARAGAUSS
Authors: Fuchs Monika S. K. , Shor Alexey M. , Rösch Notker
Published: August 2002

The parallel density functional program PARAGAUSS has been extended by a tool for computing solvent effects based on the conductor‐like screening model (COSMO). The molecular cavity in the solvent is constructed as a set of overlapping spheres according to the GEPOL algorithm. The cavity tessellation scheme and the resulting set of point charges on the cavity surface comply with the point group symmetry of the solute. Symmetry is exploited to reduce the computational effort of the solvent model. To allow an automatic geometry optimization including solvent effects, care has been taken to avoid discontinuities due to the discretization (weights of tesserae, number of spheres created by GEPOL). In this context, an alternative definition for the grid points representing the tesserae is introduced. In addition to the COSMO model, short‐range solvent effects are taken into account via a force field. We apply the solvent module to all‐electron scalar‐relativistic density functional calculations on uranyl, UO22+, and its aquo complexes in aqueous solution. Solvent effects on the geometry are very small. Based on the model [UO2(H2O)5]2+, the solvation energy of uranyl is estimated to be about −400 kcal/mol, in agreement with the range of experimental data. The major part of the solvation energy, about −250 kcal/mol, is due to a donor–acceptor interaction associated with a coordination shell of five water ligands. One can interpret this large solvation energy also as a compounded effect of an effective reduction of the uranyl moiety plus a solvent polarization. The energetic effect of the structure relaxation in the solution is only about 8 kcal/mol. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Dynamics of the D2 + Ni(100) collision system: Analysis of the reactive and inelastic channels
Authors: Böyükata M. , Güvenç Z. B. , Jackson B. , Jellinek J.
Published: August 2002

The reactive and scattering channels of the D2(v,j)+Ni(100) collision system are studied using quasiclassical molecular dynamics simulations. The interaction between the D2 and the atoms of the surface is modeled by a LEPS (London–Eyring–Polani–Sato) potential energy function. The molecule is aimed at three different impact sites (atop, bridge, and center) of a rigid Ni(100) surface along the normal direction with various collision energies ≤1.0 eV. Dissociative chemisorption probabilities are computed for different rotational states of the molecule. Probability distributions of the final rovibrational states of the ground‐state D2 molecule scattered from those impact sites are also computed as a function of the collision energy. Higher collision energy results in excitation of higher rotational and/or vibrational states of the scattered molecule. At collision energies below 0.1 eV an indirect dissociation mechanism (through molecular adsorption) dominates the reaction. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 84: 48–57, 2001
Quantum coherent control of Coulomb enhancement by two‐color pulseshaping
Authors: Pötz Walter
Published: August 2002

Pulse shaping based on two‐color optical excitation is shown to provide a versatile coherent control scheme for electron inter(sub)band transitions in semiconductors. In semiconductor heterostructures, this control scheme provides both phase‐sensitive absorption and exciton formation, as well as interwell tunneling of photoexcited charge carriers. Our microscopic analysis shows that this control mechanism is due to a combination of many‐body effects arising from the coherent part of the electron–electron Coulomb interaction and pulse‐shaping arising from the spectral overlap between the two pulses. This control mechanism is applicable to a wide range of semiconductors, both bulk and low‐dimensional structures, and may have a practical application for phase sensitive absorbers and the generation of THz radiation. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Quantal density functional theory of excited states: Application to an exactly solvable model
Authors: Slamet Marlina , Sahni Viraht
Published: August 2002

The quantal density functional theory (Q‐DFT) of excited states is the description of the physics of the mapping from any bound nondegenerate excited state of Schrödinger theory to that of the s‐system of noninteracting Fermions with equivalent density ρk(r), energy Ek, and ionization potential Ik. The s‐system may either be in an excited state with the same configuration as in Schrödinger theory or in a ground state with a consequently different configuration. The Q‐DFT description of the s‐system is in terms of a conservative field ℱk(r), whose electron‐interaction ℰee(r) and correlation‐kinetic 𝒵(r) components are separately representative of electron correlations due to the Pauli exclusion principle and Coulomb repulsion, and correlation‐kinetic effects, respectively. The sources of these fields are expectations of Hermitian operators taken with respect to the system wavefunction. The local electron‐interaction potential vee(r) of the s‐system, representative of all the many‐body correlations, is the work done to move an electron in the force of the field ℱk(r). The electron interaction Eee and correlation‐kinetic Tc components of the total energy Ek may be expressed in integral virial form in terms of their respective fields. The difference between the s‐system in its ground or excited state representation is due entirely to correlation‐kinetic effects. The highest occupied eigenvalue of the s‐system differential equation in either case is minus the ionization potential Ik. In this work we demonstrate the transformation of an excited state of Schrödinger theory, as represented by the first excited singlet state of the exactly solvable Hooke's atom, to that of noninteracting Fermions in their ground state with equivalent excited state density, energy, and ionization potential. To further prove the Fermions are in a ground state, we solve the corresponding singlet s‐system differential equation numerically for the vee(r) determined, and obtain the excited state density from the zero node orbitals generated. The resulting total energy is also the same. In addition, the single eigenvalue determined corresponds to minus the ionization potential of the excited state. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Symmetry and degeneracy in density functional theory
Authors: Katriel Jacob , Zahariev Federico , Burke Kieron
Published: August 2002

The superhamiltonian formalism is used to construct a totally symmetric superdensity for a system whose ground state corresponds to a multidimensional irreducible representation of the symmetry group of the Hamiltonian. A Hohenberg–Kohn theorem is proven and the Levy constrained‐search procedure is adapted. An appropriate generalization allows the application of this procedure to degenerate excited states. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Spectroscopic and quantum chemical study on electronic and geometric properties of free and embedded dithizone molecules
Authors: Schönherr T. , Linder R. , Rosellen U. , Schmid V.
Published: August 2002

The molecular and electronic structure of the three tautomeric forms of dithizone has been calculated by using semiempirical, density functional theory (DFT), and ab initio methods. Comparison of ground‐state energies shows the symmetric form most stabilized, but there is only a small barrier (<3 kcal/mol) for the hydrogen transfer from NH toward HS (enol form). For understanding the origin of the optical transitions intermolecular interactions have to be taken into account. By using the supermolecule method, the absorption band pattern can be rationalized already on the level of the PM3 model. The nuclear magnetic resonance (NMR) solution spectrum is interpreted in terms of an equilibrium between the symmetric and the enol forms of dithizone. The appearance of strong EPR signals only for the solid state reflects a considerable lowering of the triplet state (symmetric form). Experimental features are discussed in view of calculated energies (stabilization), chemical shifts (NMR), and SOMO orbitals (EPR). © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Moving pieces in a proteomic puzzle: mass fingerprinting of toxic fractions from the venom of Tityus serrulatus (Scorpiones, Buthidae)
Authors: Pimenta Adriano M. C. , Stöcklin Reto , Favreau Philippe , Bougis Pierre E. , Martin‐Eauclaire Marie‐France
Published: August 2002

Scorpion venoms are very complex mixtures of molecules, most of which are peptides that display different kinds of biological activity. These venoms have been studied in the light of their pharmacological targets and their constituents are able to bind specifically to a variety of ionic channels located in prey tissues, resulting in neurotoxic effects. Toxins that modulate Na+, K+, Ca++ and Cl− currents have been described in scorpion venoms. Mass spectrometry was employed to analyze toxic fractions from the venom of the Brazilian scorpion Tityus serrulatus in order to shed light on the molecular composition of this venom and to facilitate the search for novel pharmacologically active compounds. T. serrulatus venom was first subjected to gel filtration to separate its constituents according to their molecular size. The resultant fractions II and III, which account for 90 and 10% respectively of the whole venom toxic effect, were further analyzed by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS), on‐line liquid chromatography/electrospray mass spectrometry (LC/ESMS) and off‐line LC/MALDI‐TOFMS in order to establish their mass fingerprints. The molecular masses in fraction II were predominantly between 6500 and 7500 Da. This corresponds to long‐chain toxins that mainly act on voltage‐gated Na+ channels. Fraction III is more complex and predominantly contained molecules with masses between 2500 and 5000 Da. This corresponds to the short‐chain toxin family, most of which act on K+ channels, and other unknown peptides. Finally, we were able to measure the molecular masses of 380 different compounds present in the two fractions investigated. To our knowledge, this is the largest number of components ever detected in the venom of a single animal species. Some of the toxins described previously from T. serrulatus venom could be detected by virtue of their molecular masses. The interpretation of this large set of data has provided us with useful proteomic information on the venom, and the implications of these findings are discussed. Copyright © 2001 John Wiley & Sons, Ltd.
Ready‐made matrix‐assisted laser desorption/ionization target plates coated with thin matrix layer for automated sample deposition in high‐density array format
Authors: Miliotis Tasso , Kjellström Sven , Nilsson Johan , Laurell Thomas , Edholm Lars‐Erik , Marko‐Varga György
Published: August 2002

The methodology for ready‐made matrix‐assisted laser desorption/ionization (MALDI) target plates covered with an optimized thin layer consisting of matrix and nitrocellulose has been developed. Piezoelectric microdispensing enabled sample depositions in a high‐density array format of 2000 sample depositions on a conventionally sized target plate (45 × 47 mm). The sample depositions were made reproducibly in a fully automated mode by using an in‐house developed computer‐controlled piezoelectric flow‐through microdispenser. Additionally, the piezoelectric technique facilitated significant analyte enrichment that increased the detection sensitivity. The MS signal was obtained rapidly, generally within ten laser pulses. An airbrush device was used to generate a fine spray of matrix and nitrocellulose dissolved in acetone. The acetone evaporated instantly when reaching the target plate leaving the entire surface with a thin and uniform matrix/nitrocellulose coating consisting of very small crystals of matrix embedded in the nitrocellulose. These crystals acted as a seed‐layer on subsequent analyte depositions, rendering homogeneous sample spots when using α‐cyano‐4‐hydroxycinnamic acid (CHCA) as matrix. The relative standard deviation of the signal intensity between spots was (20–30)% (n = 30). The detection sensitivity was improved by restricting the sample spot diameter to 300 µm. The spot size was affected by the deposition rate and the evaporation rate of the dispensed sample volume. Mass spectra of a 25‐amol peptide mixture deposition were successfully recorded. Copyright © 2001 John Wiley & Sons, Ltd.
Atmospheric pressure laser desorption/chemical ionization mass spectrometry: a new ionization method based on existing themes
Authors: Coon Joshua J. , McHale Kevin J. , Harrison W. W.
Published: August 2002

We have designed and constructed an atmospheric pressure laser desorption/chemical ionization (AP‐LD/CI) source that utilizes a laser pulse to desorb intact neutral molecules, followed by chemical ionization via reagent ions produced by a corona discharge. This source employs a heated capillary atmospheric pressure inlet coupled to a quadrupole ion trap mass spectrometer and allows sampling under normal ambient air conditions. Preliminary results demonstrate that this technique provides ∼150‐fold increase in analyte ions compared to the ion population generated by atmospheric pressure infrared matrix‐assisted laser desorption/ionization (AP‐IR‐MALDI). Copyright © 2002 John Wiley & Sons, Ltd.
Mass spectrometric fragmentation of cyclic peptides belonging to the polymyxin and colistin antibiotics studied by ion trap and quadrupole/orthogonal‐acceleration time‐of‐flight technology
Authors: Govaerts Cindy , Rozenski Jef , Orwa Jennifer , Roets Eugène , Schepdael Ann Van , Hoogmartens Jos
Published: August 2002

Electrospray ionization linked to quadrupole/orthogonal‐acceleration time‐of‐flight (Q/oaTOF) and ion trap equipment was used to study the fragmentation behavior of the linear side‐chain cyclized peptides of the polymyxin B and E antibiotics. This study exemplifies both the benefits and the drawbacks of mass spectrometric techniques for the determination of the sequence of such complex linear side‐chain cyclized peptides. Q/oaTOF accurate mass measurements did not help sufficiently to assign the product ions observed in the product ion spectra. An ion trap mass spectrometer providing MSn capability was used to eliminate ambiguities encountered with a single MS/MS approach. The complex fragmentation behavior of these compounds of well‐established structure is described which could be useful for structural characterization of unknown substances related to polymyxin B and E in the future. Copyright © 2002 John Wiley & Sons, Ltd.
Liquid chromatography and electron‐capture dissociation in Fourier transform ion cyclotron resonance mass spectrometry
Authors: Palmblad Magnus , Tsybin Youri O. , Ramström Margareta , Bergquist Jonas , Håkansson Per
Published: August 2002

Liquid separation methods in combination with electrospray mass spectrometry as well as the recently introduced fragmentation method electron capture dissociation (ECD) have become powerful tools in proteomics research. This paper presents the results of the first successful attempts to combine liquid chromatography (LC) and Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) with ECD in the analysis of a mixture of standard peptides and of a bovine serum albumin tryptic digest. A novel electron injection system provided conditions for ECD sufficient to yield extensive sequence information for the most abundant peptides in the mixtures on the time‐scale of the chromatographic separation. The results suggest that LC/ECD‐FTICRMS can be employed in the characterization of peptides in enzymatic digests of proteins or protein mixtures and identify and localize posttranslational modifications. Copyright © 2002 John Wiley & Sons, Ltd.
Headspace solid‐phase microextraction gas chromatography/mass spectrometry in the analysis of the aroma constituents of ‘Cannonau of Jerzu’ wine
Authors: Begala Michela , Corda Luciana , Podda Gianni , Fedrigo Maria Anna , Traldi Pietro
Published: August 2002

“Cannonau of Jerzu” wine is a typical Sardinian product, obtained from only one particular grape variety. Its aroma profile is highly characteristic from the organoleptic point of view but, until now, no analytical investigation of the aroma components has been reported. This aspect has been studied by headspace solid‐phase microextraction coupled with gas chromatography/mass spectrometry (GC/MS). Using this approach, 76 abundant aroma components were identified. The results thus obtained show on one hand that the terpene profile is, as expected, dependent on the quality of the grapes (in terms of selection before vintage), and, on the other, that some components are strongly dependent on the production and ageing method. Copyright © 2002 John Wiley & Sons, Ltd.
Evaluation of low‐pressure gas chromatography linked to ion‐trap tandem mass spectrometry for the fast trace analysis of multiclass pesticide residues
Authors: González‐Rodríguez M. J. , Garrido‐Frenich A. , Arrebola F. J. , Martínez‐Vidal J. L.
Published: August 2002

A rapid multiresidue method for the analysis of 72 pesticides has been developed using a single injection with low‐pressure gas chromatography/tandem mass spectrometry (LP‐GC/MS/MS). The LP‐GC/MS/MS method used a short capillary column of 10 m × 0.53 mm i.d. × 0.25 µm film thickness coupled with a 0.6 m × 0.10 mm i.d. restriction at the inlet end. Optimal LP‐GC conditions were determined which achieved the fastest separation in MS/MS detection mode. Also MS/MS conditions were optimized in order to increase sensitivity and selectivity. The analytical parameters of the LP‐GC/MS/MS method were compared with those obtained by GC/MS/MS using a conventional capillary column (30 m × 0.25 mm i.d. × 0.25 µm film thickness). Better precision and sensitivity values were obtained with the LP‐GC/MS/MS approach. The limits of detection (LOD) of the compounds ranged from 0.1 to 14.1 µg L−1 for LP‐GC/MS/MS, lower than those obtained for conventional GC/MS/MS that ranged from 0.1 to 17.5 µg L−1. The peak widths obtained with the short column in LP‐GC are similar to those obtained using conventional capillary GC columns, and the peaks can be successfully identified by MS/MS detection with the conventional scan speed of ion‐trap instruments. In addition, the analysis time was significantly reduced with LP‐GC/MS/MS (32 min) versus GC/MS/MS (72 min), allowing the number of samples analyzed per day in a routine laboratory to be doubled. Copyright © 2002 John Wiley & Sons, Ltd.
Towards a human Lassa fever vaccine
Authors: Fisher‐Hoch S. P. , McCormick J. B.
Published: August 2002

Arenaviruses, such as Lassa fever, establish chronic infections in rodents, leading to incidental transmission to humans. Lassa fever is a clinically severe disease, yet the absence of second attacks implies life‐long immunity. The aim of this review is to consider whether such immunity could be provided by vaccines. The South American arenaviruses are controlled by neutralising antibody and a clinical trial of live, attenuated vaccine for Argentinian haemorrhagic fever provided 84% protection. In contrast, there is no evidence for protective humoral immunity against Old World arenaviruses which are controlled by cell‐mediated immune responses. Nevertheless, vaccination with Lassa glycoproteins can protect monkeys from disease, implying that protection may be achievable, even though the immunological mechanisms are distinct. Recombinant vaccinia viruses expressing various forms of Lassa glycoproteins can protect both guinea‐pigs and primates, while additional protective responses can be mounted against nucleocapsid genes. However, vaccines based upon vaccinia constructs are no longer tenable for African populations with a high seroprevalence of HIV infection. The scientific challenge now remains to find alternative methods of delivering T‐cell immunity against glycoproteins from Lassa virus in ways which can overcome the local economic and political hurdles to vaccine development. Copyright © 2001 John Wiley & Sons, Ltd.
Kinematics of a new spherical parallel manipulator with three equal legs: The 3‐URC wrist
Authors: Di Gregorio Raffaele
Published: August 2002

Parallel manipulators are constituted of two rigid bodies, one movable (platform) and the other fixed (base), connected by a number of kinematic chains (legs). Manipulators with all equal legs that have the actuators adjacent to the base allow the use of simplified design procedures and manufacturing processes. Moreover, they are able to reach high performances. Further manufacturing simplifications can be obtained if only revolute pairs and passive cylindrical pairs are used. This article presents a new spherical parallel manipulator, named the 3‐URC wrist. The 3‐URC wrist is not overconstrained. It has three equal legs having only passive cylindrical pairs and revolute pairs with the actuators adjacent to the base. The 3‐URC wrist mounting and manufacturing conditions making spherical motions of the platform possible are defined. Then the position analysis and the mobility analysis of the 3‐URC wrist are solved. Finally, the singularity conditions are written in explicit form and geometrically interpreted. © 2001 John Wiley & Sons, Inc.
Phase transition and finite‐size scaling for the integer partitioning problem
Authors: Borgs Christian , Chayes Jennifer , Pittel Boris
Published: August 2002

We consider the problem of partitioning n randomly chosen integers between 1 and 2m into two subsets such that the discrepancy, the absolute value of the difference of their sums, is minimized. A partition is called perfect if the optimum discrepancy is 0 when the sum of all n integers in the original set is even, or 1 when the sum is odd. Parameterizing the random problem in terms of κ=m/n, we prove that the problem has a phase transition at κ=1, in the sense that for κ<1, there are many perfect partitions with probability tending to 1 as n→∞, whereas for κ>1, there are no perfect partitions with probability tending to 1. Moreover, we show that this transition is first‐order in the sense the derivative of the so‐called entropy is discontinuous at κ=1.

We also determine the finite‐size scaling window about the transition point: κn=1−(2n)−1 log2 n+λn/n, by showing that the probability of a perfect partition tends to 1, 0, or some explicitly computable p(λ)∈(0, 1), depending on whether λn tends to −∞, ∞, or λ∈(−∞, ∞), respectively. For λn→−∞ fast enough, we show that the number of perfect partitions is Gaussian in the limit. For λn→∞, we prove that with high probability the optimum partition is unique, and that the optimum discrepancy is Θ(2). Within the window, i.e., if |λn| is bounded, we prove that the optimum discrepancy is bounded. Both for λn→∞ and within the window, we find the limiting distribution of the (scaled) discrepancy. Finally, both for the integer partitioning problem and for the continuous partitioning problem, we find the joint distribution of the k smallest discrepancies above the scaling window. © 2001 John Wiley & Sons, Inc. Random Struct. Alg., 19: 247–288, 2001
The Random‐Facet simplex algorithm on combinatorial cubes
Authors: Gärtner Bernd
Published: August 2002

The RANDOM‐FACET algorithm is a randomized variant of the simplex method which is known to solve any linear program with n variables and m constraints using an expected number of pivot steps which is subexponential in both n and m. This is the theoretically fastest simplex algorithm known to date if m ≈ n; it provably beats most of the classical deterministic variants which require exp(Ω(n)) pivot steps in the worst case. RANDOM‐FACET has independently been discovered and analyzed ten years ago by Kalai as a variant of the primal simplex method, and by Matous̆ek, Sharir, and Welzl in a dual form. The essential ideas and results connected to RANDOM‐FACET can be presented in a particularly simple and instructive way for the case of linear programs over combinatorial n‐cubes. I derive an explicit upper bound of

on the expected number of pivot steps in this case, using a new technique of “fingerprinting” pivot steps. This bound also holds for generalized linear programs, similar flavors of which have been introduced and studied by several researchers. I then review an interesting class of generalized linear programs, due to Matous̆ek, showing that RANDOM‐FACET may indeed require an expected number of $\exp \bigl(\Omega\bigl(\sqrt n\bigr)\bigr)$ pivot steps in the worst case. The main new result of the paper is a proof that all actual linear programs in Matous̆ek's class are solved by RANDOM‐FACET with an expected polynomial number of $O \bigl(n^2 \bigr)$ pivot steps. This proof exploits a combinatorial property of linear programming which has only recently been discovered by Holt and Klee. The result establishes the first scenario in which an algorithm that works for generalized linear programs “recognizes” proper linear programs. Thus, despite Matous̆ek's worst‐case result, the question remains open whether RANDOM‐FACET (or any other simplex variant) is a polynomial‐time algorithm for linear programming. Finally, I briefly discuss extensions of the combinatorial cube results to the general case. © 2002 Wiley Periodicals, Inc. Random Struct. Alg., 20:353–381, 2002
The degree sequence of a scale‐free random graph process
Authors: Bollobás B´ela , Riordan Oliver , Spencer Joel , Tusnády Gábor
Published: August 2002

Recently, Barabási and Albert [2] suggested modeling complex real‐world networks such as the worldwide web as follows: consider a random graph process in which vertices are added to the graph one at a time and joined to a fixed number of earlier vertices, selected with probabilities proportional to their degrees. In [2] and, with Jeong, in [3], Barabási and Albert suggested that after many steps the proportion P(d) of vertices with degree d should obey a power law P(d)αd−γ. They obtained γ=2.9±0.1 by experiment and gave a simple heuristic argument suggesting that γ=3. Here we obtain P(d) asymptotically for all d≤n1/15, where n is the number of vertices, proving as a consequence that γ=3. © 2001 John Wiley & Sons, Inc. Random Struct. Alg., 18, 279–290, 2001
On the chromatic number of set systems
Authors: Kostochka Alexandr , Mubayi Dhruv , Rödl Vojtěch , Tetali Prasad
Published: August 2002

An (r, l)‐system is an r‐uniform hypergraph in which every set of l vertices lies in at most one edge. Let mk(r, l) be the minimum number of edges in an (r, l)‐system that is not k‐colorable. Using probabilistic techniques, we prove that

where br, l is explicitly defined and ar, l is sufficiently small. We also give a different argument proving (for even k)

where a′r, l=(r−l+1)/r(2r−1re)−l/(l−1).

Our results complement earlier results of Erdős and Lovász [10] who mainly focused on the case l=2, k fixed, and r large. © 2001 John Wiley & Sons, Inc. Random Struct. Alg., 19: 87–98, 2001
Bathtub dynamics: initial results of a systems thinking inventory
Authors: Sweeney Linda Booth , Sterman John D.
Published: August 2002

In a world of accelerating change, educators, business leaders, environmentalists and scholars are calling for the development of systems thinking to improve our ability to take effective actions. Through courses in the K‐12 grades, universities, business schools, and corporations, advocates seek to teach people to think systemically. These courses range from one‐day workshops with no mathematics to graduate level courses stressing formal modeling. But how do people learn to think systemically? What skills are required? Does a particular type of academic background improve one's ability to think systemically? What systems concepts are most readily understood? Which tend to be most difficult to grasp? We describe initial results from an assessment tool or systems thinking inventory. The inventory consists of brief tasks designed to assess particular systems thinking concepts such as feedback, delays, and stocks and flows. Initial findings indicate that subjects from an elite business school with essentially no prior exposure to system dynamics concepts have a poor level of understanding of stock and flow relationships and time delays. Performance did not vary systematically with prior education, age, national origin, or other demographic variables. We hope the inventory will eventually provide a means for testing the effectiveness of training and decision aids used to improve systems thinking skills. We discuss the implications of these initial results and explore steps for future research. Copyright © 2000 John Wiley & Sons, Ltd.
Adsorption and desorption of benzene on Si(111)‐7 × 7 studied by scanning tunnelling microscopy
Authors: Kawasaki Toyosei , Sakai Daisuke , Kishimoto Hiroshi , Akbar Ade Asneil , Ogawa Takashi , Oshima Chuhei
Published: August 2002

The atomic‐scale processes of benzene adsorption and desorption on an Si(111)‐7 × 7 surface have been investigated with scanning tunnelling microscopy. Analysis of the atomic‐scale images obtained during the adsorption and desorption processes yielded the following results: benzene molecules adsorbed on Si(111)‐7 × 7 with the di‐σ bonds between molecules and two Si atoms, an adatom and a rest atom; and benzene molecules chemisorb and desorb through physisorption states. Copyright © 2001 John Wiley & Sons, Ltd.
Heterogeneity in phase I clinical trials: prior elicitation and computation using the continual reassessment method
Authors: Legedza Anna T. R. , Ibrahim Joseph G.
Published: August 2002

Heterogeneity in a phase I clinical trial patient population may lead to distinctly different dose–response relationships along covariate values. For a given target probability of toxicity, this implies different maximum tolerated doses (MTDs) for each distinct subpopulation. Within the framework of O'Quigley, Pepe and Fisher's (1990) continual reassessment method, we propose the notion of average and patient‐specific MTDs by augmenting the dose–response model with other covariates to account for such differences. A method to elicit prior distributions on the dose and other covariate parameters are proposed, based on the predictive approach of Ibrahim and Laud (1994), Laud and Ibrahim (1995), and Ibrahim, Ryan and Chen (1998). This approach relies on prior predictions for the response vector y0 and a quantity a0 specifying uncertainty in y0. Then, y0 and a0 are used to specify a prior for the regression coefficients in a semi‐automatic fashion. The elicitation scheme for y0 uses results from previous phase I cancer clinical trials. The average and patient‐specific MTDs and an elicitation method are demonstrated in logistic regression examples. Copyright © 2001 John Wiley & Sons, Ltd.
Statistical cost‐effectiveness analysis of two treatments based on net health benefits
Authors: Laska Eugene M. , Meisner Morris , Siegel Carole , Wanderling Joseph
Published: August 2002

Statistical methods for cost‐effectiveness analysis (CEA) for two treatments that mimic the deterministic optimal rules of CEA are presented. In these rules the objective is to determine the treatment with the maximal effectiveness whose unit cost is less than an amount, λ, that a decision‐maker is willing to pay (WTP). This is accomplished by identifying the treatment with the largest positive net health benefit (NHB), which is a function of λ, while controlling the familywise error rate both when the WTP value is given and when it is unspecified. Fieller's theorem is used to determine a region of WTP values where the NHBs of the treatments are not distinguishable. For each λ outside of the confidence region, the larger treatment is identified. A newly developed one‐tailed analogue of Fieller's theorem is used to determine the WTP values where a treatment's NHB is positive. The situation in which both treatments are experimental is distinguished from the case where one of the treatments is usual care. The one‐tailed confidence region is used in the latter case to obtain the λ values where the NHBs are not different, and determining the region of positivity of the NHBs may be unnecessary. An example is presented in which the cost‐effectiveness of two antipsychotic treatments is evaluated. Copyright © 2001 John Wiley & Sons, Ltd.