bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of the crystallinity of polyethylene/α‐olefin copolymers by thermal analysis: Relationship of the heat of fusion of 100% polyethylene crystal and the density
Authors: Mirabella Francis M. , Bafna Ayush
Published: October 2002

The heat of fusion measured with differential scanning calorimetry (DSC) is typically divided by a constant value of the heat of fusion of 100% polyethylene (PE) crystal (ΔH) for the estimation of the fraction crystallinity of PE copolymers, regardless of the density [i.e., the short‐chain branching (SCB) concentration]. In this work, values of ΔH of about 288 J/g were determined with a combined DSC and X‐ray diffraction (XRD) method for a series of PE copolymers containing SCB from 0 to 50 Br/1000 C (density = 0.965–0.865 g/cc). There was no systematic change in ΔH observed across this density range. This result supports the suitability of determining the fraction crystallinity of PE of any density by the simple division of the observed heat of fusion determined by DSC by a constant value of ΔH. This DSC method yielded values of PE crystallinity in good agreement with corresponding values determined by XRD for a series of PE copolymers. The determination of ΔH involved a small precision error for higher density (lower SCB) PEs, but the precision error increased for lower density (i.e., higher SCB) PEs. This was due to the difficulty in measuring the heat of fusion for lower density PEs, which exhibited low values of the heat of fusion and melted only slightly above room temperature, and due to the difficulty of measuring lower values of crystallinity by XRD. The crystal thickness measured by small‐angle X‐ray scattering for this series of PE copolymers decreased exponentially from about 280 to 6 Å. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1637–1643, 2002
Mechanism of the diffusion of sulfur mustard, a chemical warfare agent, in butyl and nitrile rubbers
Authors: Dubey Vinita , Gupta A. K. , Maiti S. N.
Published: October 2002

The diffusion of sulfur mustard (SM), a chemical warfare agent, through butyl (IIR) and nitrile (NBR) rubber membranes was studied with a standard spot disc breakthrough time test at temperatures ranging from 298 to 333 K. The mechanism of diffusion was interpreted on the basis of an Arrhenius relation and dynamic adsorption theory. The permeant SM was pictured to reversibly dwell at each adsorption site for about 1.5 × 10−13 s and hop randomly through the polymer matrices in small steps, with jump lengths of the order of a picometer. A comparatively lower activation energy, a solubility parameter closer to that of SM, and a lower thermodynamic interaction parameter also contributed toward faster uptake of SM by NBR in comparison with IIR. The diffusion data were also used to derive the collision diameter of SM in these polymer matrices. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1821–1827, 2002
Implications of a Middle Pleistocene ice‐wedge cast at Trimingham, Norfolk, eastern England
Authors: Whiteman Colin
Published: October 2002

A wedge exposed at Trimingham, northeast Norfolk, UK, in 1998 is interpreted as an ice‐wedge pseudomorph indicating that permafrost was present in the surrounding Cromer Forest‐bed Formation sediments. The wedge is overlain by North Sea Drift Formation (NSDF) glacial sediments, demonstrating that the associated ice sheet deposited till in either a terrestrial or an extremely shallow glaciolacustrine/marine environment. This conclusion supports those who believe that this ice sheet was, at least initially, terrestrial at this location. If the wedge is stratigraphically equivalent to the early Anglian soil stratigraphic unit, the Barham Soil, then none of the NSDF tills can be older than the Anglian/Elsterian Stage (MIS 12). Copyright © 2002 John Wiley & Sons, Ltd.
Physical and chemical characteristics of the active layer and permafrost, Herschel Island, western Arctic Coast, Canada
Authors: Kokelj S. V. , Smith C. A. S. , Burn C. R.
Published: October 2002

Physical and geochemical characteristics of near‐surface permafrost and the impact of permafrost degradation on soil and water chemistry were investigated at five sites on Herschel Island, Yukon Territory. The distribution of soluble cations, moisture and organic matter content in turbic cryosols from undisturbed terrain indicated a thaw unconformity 50 to 80 cm below the base of the present active layer. Palaeoactive‐layer depth, estimated at between 90 and 100 cm, is less than at comparable sites in the Mackenzie Delta area. The difference may be due to the comparative proximity of Herschel Island to the Beaufort Sea coastline in the early Holocene. Soluble cations in permafrost and the active layer of static cryosols at recently disturbed sites were two orders of magnitude higher than in the active layer at undisturbed sites. Na+ was the dominant cation in undisturbed permafrost, recently disturbed ground, and surface runoff derived from disturbed areas. Although degradation of permafrost following terrain disturbance has resulted in surface salinization, a condition detrimental to vegetation growth, leaching of soluble salts from disturbed areas has occurred over time. These processes have produced a range of soil conditions that contribute to the floristic diversity of Herschel Island. Copyright © 2002 John Wiley & Sons, Ltd.
Multiple cavitating pulmonary nodules and clubbing in a 12‐year‐old girl
Authors: Horak Elisabeth , Olinsky A. , Chow C.W. , Waters K. , Sawyer S.M.
Published: October 2002

We report on a 12‐year‐old girl with a prolonged history of cough and hemoptysis on three occasions. X‐ray and computed tomography of the chest showed several cavitating lesions and mediastinal lymphadenopathy. Lung biopsy revealed nodular sclerosing Hodgkin's disease. Hodgkin's disease should be considered in the differential diagnosis of cavitating pulmonary lesions. Pediatr Pulmonol. 2002; 34:147–149. © 2002 Wiley‐Liss, Inc.
Impact of respiratory illness on expiratory flow rates in normal, asthmatic, and allergic children
Authors: Rappaport Edward B. , Gilliland Frank D. , Linn William S. , Gauderman W. James
Published: October 2002

We examined the effects of current respiratory illness (RI) on pulmonary function (PF) in 1,103 subjects who underwent spirometry at schools twice within a 4‐month period. Before spirometry, subjects were asked if they had a “cold or other chest illness” during the previous month, and if so, whether they had fully recovered. Those who had not recovered were considered to have an RI.

We found that children without RI at their first PF test who reported RI on retest had significantly lower forced expiratory volume in 1 sec (FEV1) (−0.8%), peak expiratory flow rate (PEFR) (−2.2%), forced expiratory flow between 25–75% of vital capacity (FEF25–75) (−3.5%), and forced expiratory flow at 75% of vital capacity (FEF75) (−5.1%) than those without RI on both test and retest. Restriction of subjects to those without a history of doctor‐diagnosed asthma did not appreciably change these findings. Children with hay fever had significantly larger RI‐associated decreases for FEV1, FEF25–75, and FEF75, but not PEFR, than those without hay fever. Among asthmatic subjects, those with active asthma had larger RI‐associated decreases in FEF25–75 and FEF75, but not PEFR, than those without asthma. There was limited evidence that small airway losses were greater in children less than 12.5 years old.

We conclude that RI in children who are well enough to attend school may reduce expiratory flow rates. These effects are greater for children with active asthma or hay fever than in those without, and may be inversely related to age. Pediatr Pulmonol. 2002; 34:112–121. © 2002 Wiley‐Liss, Inc.
Prediagnostic toenail cadmium and zinc and subsequent prostate cancer risk
Authors: Platz Elizabeth A. , Helzlsouer Kathy J. , Hoffman Sandra C. , Morris J. Steven , Baskett Connie K. , Comstock George W.
Published: October 2002

BACKGROUND

Cadmium is a recognized human lung carcinogen that has also been positively associated with prostate cancer mainly in occupationally exposed men. The association between dietary and supplemental zinc intake and prostate cancer has not been consistent in epidemiologic studies. We evaluated the association between prediagnostic toenail cadmium and zinc concentrations and risk of prostate cancer in a cohort in which the primary route of exposure to cadmium and zinc is the diet.

METHODS

Included in the analysis were 115 prostate cancer cases and 227 age‐matched controls nested in the prospective CLUE II study located in Washington County, MD. Participants provided toenail samples at baseline in 1989. Furnace atomic absorption and flame atomic absorption were used to determine toenail cadmium and zinc concentrations, respectively. Odds ratios (OR) and 95% confidence intervals (CI) were estimated from conditional logistic regression models.

RESULTS

Median toenail cadmium and zinc concentrations did not statistically significantly differ between prostate cancer cases (cadmium, 45.9 ppb; zinc, 155.3 ppm) and controls (cadmium, 54.5 ppb; zinc, 164.0 ppm). Prostate cancer risk did not increase with increasing concentrations of cadmium (P trend = 0.9) and did not decrease with increasing concentrations of zinc (P trend = 0.2). For both metals, the ORs for the top four fifths were each below 1.0 when compared with the bottom fifth.

CONCLUSION

Men who have high toenail cadmium concentrations in the range observed in this general population sample were not at an increased risk for prostate cancer. Although there was no evidence of a linear dose‐response, these findings suggest that risk of prostate cancer may be slightly lower among men with moderate and higher zinc intake. Prostate 52: 288–296, 2002. © 2002 Wiley‐Liss, Inc.
Free‐energy simulations of the oxidation of c‐terminal methionines in calmodulin
Authors: Jas Gouri S. , Kuczera Krzysztof
Published: October 2002

In the course of aging or under conditions of oxidative stress, methionine residues of calmodulin undergo oxidation, leading to loss of biological activity of the protein. We have performed free‐energy simulations of the effects of C‐terminal methionine side‐chain oxidation on the properties of calmodulin. The simulation results indicate that oxidation should have a destabilizing effect on all three protein functional states: calcium free, calcium loaded, and with both calcium and target peptide bound. Because the different states are destabilized by different amounts, this leads to a more complex pattern in the observable effects on protein thermal stability, calcium affinity, and binding of a target peptide. The influence of oxidation on the free energy of CaM unfolding is estimated by comparing the free‐energy cost of oxidizing a Met residue in a Gly‐Met‐Gly peptide and in the protein. The protein thermal stability of the oxidized forms is lowered by a moderate amount 1–3 kcal/mol, in qualitative agreement with experimental results of 0.3 kcal/mol. The calculated changes in affinity for calcium and for the target peptide show opposing trends. Oxidation at position 144 is predicted to enhance peptide binding and weaken calcium binding, whereas oxidation at 145 weakens peptide binding and enhances affinity for calcium. The lower affinity of Met 145‐oxidized calmodulin toward the target peptide correlates with experimentally observed lowering of calmodulin‐activated Ca‐ATPase activity when oxidized calmodulin from aged rat brains is used. Thus, our simulations suggest that Met 145 is the oxidation site in the C‐terminal fragment of calmodulin. The microscopic mechanism behind the calculated free energy changes appears to be a greater affinity for water of the oxidized Met side‐chain relative to normal Met. Structures with Met exposed to solvent had consistently lower free energies than those with buried Met sidechains. Proteins 2002;48:257–268. © 2002 Wiley‐Liss, Inc.
The role of hydrophobic microenvironments in modulating pKa shifts in proteins
Authors: Mehler E.L. , Fuxreiter M. , Simon I. , Garcia‐Moreno E B.
Published: October 2002

The screened Coulomb potential (SCP) method, combined with a quantitative description of the microenvironments around titratable groups, based on the Hydrophobic Fragmental Constants developed by Rekker, has been applied to calculate the pKa values of groups embedded in extremely hydrophobic microenvironments in proteins. This type of microenvironment is not common; but constitutes a small class, where the protein's architecture has evolved to lend special properties to the embedded residue. They are of significant interest because they are frequently important in catalysis and in proton and electron transfer reactions. In the SCP treatment these special cases are treated locally and therefore do not affect the accuracy of the pKa values calculated for other residues in less hydrophobic environments. Here the calibration of the algorithm is extended with the help of earlier results from lysozyme and of three mutants of staphylococcal nuclease (SNase) that were specially designed to measure the energetics of ionization of titratable groups buried in extremely hydrophobic microenvironments. The calibrated algorithm was subsequently applied to a fourth mutant of SNase and then to a very large dimeric amine oxidase of 1284 residues, where 334 are titratable. The observed pKa shifts of the buried residues are large (up to 4.7 pK units), and all cases are well reproduced by the calculations with a root mean square error of 0.22. These results support the hypothesis that protein electrostatics can only be described correctly and self‐consistently if the inherent heterogeneity of these systems is properly accounted for. Proteins 2002;48:283–292. © 2002 Wiley‐Liss, Inc.
Atoms‐in‐molecules study of the genetically encoded amino acids. II. Computational study of molecular geometries
Authors: Matta Chérif F. , Bader Richard F. W.
Published: October 2002

The geometries of the 20 genetically encoded amino acids were optimized at the restricted Hartree–Fock level of theory using the 6‐31+G* basis set. A detailed comparison showed the calculated geometries to be in excellent agreement with those determined by X‐ray crystallography. The study demonstrated that the geometric parameters for the main‐chain group and for the bonds and common functional groups of the side‐chains exhibit a high degree of transferability among the members of this set of molecules. This geometric transferability is a necessary prerequisite for the corresponding transferability of their electron density distributions and hence of their bond and atomic properties. The transferability of the electron distributions will be demonstrated and exploited in the following paper of this series, which uses the topology of the electron density to define an atom within the quantum theory of atoms in molecules. Particular features of the geometries of the amino acids are discussed. It has been shown, for example, how the apparent anomaly of the CαN bond length in a peptide being shorter than in the charged species CαNHis resolved when the charge separation is gauged by the differences in the charges of the Cα and N atoms as opposed to the use of formal charges. A compilation of literature sources on experimental geometries covering each member of the 20 amino acids is presented. A set of rules for labeling the atoms and bonds, complementing the generally accepted IUPAC‐IUB rules, is proposed to uniquely identify every atom and bond in the amino acids. Proteins 2002;48:519–538. © 2002 Wiley‐Liss, Inc.
Aromatic side‐chain interactions in proteins. I. Main structural features
Authors: Thomas Annick , Meurisse Rita , Charloteaux Benoit , Brasseur Robert
Published: October 2002

In a data set of 593 nonhomologous proteins from the PDB, we have analyzed the pairing of phenylalanine, tyrosine, tryptophan, and histidine residues with their closest aromatic partner. The frequency distribution of the shortest interatomic distance of partners is bimodal with a sharp peak at ∼3.8 Å and a wider one at a longer distance. Only the 3.8 Å peak corresponds to direct ring–ring interactions thus aromatic pairs. The aromatic pairs were separated into two classes, near‐sequence pairs and far‐sequence pairs. Near sequence pairs stabilize local structure, and far‐sequence pairs stabilize tertiary structure. Far‐sequence pairs (74% of all pairs) mainly bridge two β‐strands, followed by pairs that bridge a β‐strand and a helix, and pairs that bridge a β‐strand and a random coil structure. Pairs that bridge helices are rare. The secondary structure of the near‐sequence pairs depends on the partner distance in the sequence. When the partners are 1, 3, or 4 residues apart in the sequence, pairs are mostly found in helical structures. When the partners are two apart, pairs are mostly found in the same β‐strand. Analysis of the frequency of near sequence pairs supports the hypothesis that aromatic pairing occurs after, rather than before, the formation of secondary structures. Proteins 2002;48:628–634. © 2002 Wiley‐Liss, Inc.
Information‐theoretic dissection of pairwise contact potentials
Authors: Cline Melissa S. , Karplus Kevin , Lathrop Richard H. , Smith Temple F. , Rogers Robert G. , Haussler David
Published: October 2002

Pairwise contact potentials have a long, successful history in protein structure prediction. They provide an easily‐estimated representation of many attributes of protein structures, such as the hydrophobic effect. In order to improve on existing potentials, one should develop a clear understanding of precisely what information they convey. Here, using mutual information, we quantified the information in amino acid potentials, and the importance of hydropathy, charge, disulfide bonding, and burial. Sampling error in mutual information was controlled for by estimating how much information cannot be attributed to sampling bias. We found the information in amino acid contacts to be modest: 0.04 bits per contact. Of that, only 0.01 bits of information could not be attributed to hydropathy, charge, disulfide bonding, or burial. Proteins 2002;49:7–14. © 2002 Wiley‐Liss, Inc.
CysxHisyZn2+ interactions: Thiol vs. thiolate coordination
Authors: Simonson Thomas , Calimet Nicolas
Published: October 2002

In zinc proteins, the Zn2+ cation frequently binds with a tetrahedral coordination to cysteine and histidine side chains, for example, in many DNA‐binding proteins, where it plays primarily a structural role. We examine the possibility of thiolate protonation in CysxHisyZn2+ groups, both in proteins and in solution, through a combination of theoretical calculations and database analysis. Seventy‐five percent of the thiolate‐coordinated zincs in the Cambridge Structural Database are tetrahedral, while di‐alkanethiol coordination always involves five or more ligands. Ab initio quantum calculations are performed on (ethanethiol/thiolate)3imidazole‐Zn2+ complexes in vacuum, yielding geometries and gas phase basicities. Protonating one (respectively two) thiolates increases the Zn‐S(thiol) distance by 0.4 Å (respectively 0.3 Å), providing a structural marker for protonation. The stabilities of the complexes in solution are compared by combining the gas phase basicities with continuum dielectric solvation calculations. In a continuum solvent with permittivity ε = 4, 20, or 80, one of three thiolates is predicted to be protonated at neutral pH. By extension, Cys4Zn2+ groups are expected to be protonated in the same conditions. In contrast, most Cys3His and Cys4 geometries in the Protein Data Bank (PDB) appear consistent with all‐thiolate Zn2+ coordination. This apparent discrepancy is resolved by two recent surveys of zinc protein structures, which suggest that these all‐thiolate sites are stabilized by charged and polar groups nearby in the protein, thus overcoming their intrinsic instability. However, the experimental resolution is not sufficient in all the PDB structures to rule out a thiol/thiolate mixture, and protonated thiolates may occur in some proteins not solved at high resolution or not represented in the PDB, as suggested by recent mass spectrometry experiments; this possibility should be allowed for in X‐ray structure refinement. Proteins 2002;49:37–48. © 2002 Wiley‐Liss, Inc.
Iron(III) photo‐induced degradation of isoproturon: correlation between degradation and toxicity
Authors: Galichet Frédéric , Mailhot Gilles , Bonnemoy Frédérique , Bohatier Jacques , Bolte Michèle
Published: October 2002

The degradation of isoproturon photoinduced by Fe(III) was investigated under both artificial and solar light. The monomeric species Fe(OH)2+ present under the experimental conditions ([Fe(III)] = 3 × 10−4 M) is the main Fe(III) species responsible for the degradation of isoproturon. The process involves the attack on the pollutant by ·OH radicals generated by irradiation of Fe(OH)2+. The major primary photoproducts were identified; they accumulate in the solution medium before being degraded. The toxicity of the solution to marine bacterium Vibrio fisheri (Beijerinck) Lehmann & Neumann was monitored during the degradation process. It increased in the early stages of the reaction and, among the photoproducts, the N‐formyl derivative appeared to be the major product responsible for the increase in toxicity.

© 2002 Society of Chemical Industry
Preventative effects of the flowers of Inula britannica on autoimmune diabetes in C57BL/KsJ mice induced by multiple low doses of streptozotocin
Authors: Kobayashi Takao , Song Qing‐Hua , Hong Tie , Kitamura Hajime , Cyong Jong‐Chol
Published: October 2002

We have reported that an aqueous extract from the flowers of Inula britannica L. subsp. japonica Kitam. (IB) prevented immunologically induced experimental hepatitis in mice and suggested that the antihepatitic effect of IB is due to inhibition of IFN‐γ production. We then investigated the effects of IB on diabetes in mice induced by multiple low doses of streptozotocin (MLDSTZ), which is a mouse model for IFN‐γ‐dependent autoimmune diabetes. C57BL/KsJ mice (male, 7 weeks) were provided with IB extract (500 mg/ kg/ day) in drinking water ad libitum, starting 7 days before the first STZ injection. Autoimmune diabetes was induced by MLDSTZ (40 mg/kg/day for 5 daily doses, i.p.). The IB treatment significantly suppressed the increase of blood glucose levels. Histological analysis of the pancreas showed that the degree of insulitis and destruction of β‐cells were reduced by IB treatment. The IFN‐γ production from stimulated splenic T lymphocytes was inhibited by the IB treatment. Moreover, the proportion of IFN‐γ‐producing cells in the CD4+ population, which was increased by MLDSTZ, was significantly decreased by the IB treatment. These results suggest that IB has a preventative effect on autoimmune diabetes by regulating cytokine production. Copyright © 2002 John Wiley & Sons, Ltd.
Evaluation of antilipid peroxidative action of propolis ethanol extract
Authors: Shinohara Rikio , Ohta Yoshiji , Hayashi Takahiro , Ikeno Takeyuki
Published: October 2002

The antilipid peroxidative action of the ethanol extract of Brazilian propolis at a concentration of 47% (w/v) was evaluated by examining the inhibitory effect of the extract on the formation of hydroperoxide‐ and endoperoxide‐type lipid peroxides during heating of authentic polyunsaturated fatty acids and on Fe3+‐ADP/ascorbic acid‐ and Fe3+‐ADP/NADPH‐dependent lipid peroxidation reactions in rat liver microsomes. Hydroperoxide‐type lipid peroxides were measured by the haemoglobin–methylene blue method and endoperoxide‐type lipid peroxides by the thiobarbituric aicd (TBA), Fe3+‐TBA and LPO‐586 methods. Propolis ethanol extract inhibited dose‐dependently the formation of hydroperoxide‐ and endoperoxide‐type lipid peroxides during heating of linoleic acid, linolenic acid or arachidonic acid and the amount of the extract causing a half inhibition of these lipid peroxide formations ranged between 20 and 75 μg. Propolis ethanol extract inhibited dose‐dependently both Fe3+‐ADP/ascorbic acid‐ and Fe3+‐ADP/NADPH‐dependent lipid peroxidation reactions in rat liver microsomes when lipid peroxides produced in both reactions were measured by the TBA method. The amount of propolis extract causing a half inhibition of the Fe3+‐ADP/ascorbic acid‐dependent lipid peroxidation was about 5 μg, while that of the extract causing a half inhibition of the Fe3+‐ADP/NADPH‐dependent lipid peroxidation was about 0.15 μg. These results indicate that the propolis ethanol extract exerts an antilipid peroxidative action at very low doses. Copyright © 2002 John Wiley & Sons, Ltd.
Peroxynitrite scavenging activity of herb extracts
Authors: Choi Hye Rhi , Choi Jae Sue , Han Yong Nam , Bae Song Ja , Chung Hae Young
Published: October 2002

Peroxynitrite (ONOO−) is a cytotoxicant with strong oxidizing properties toward various cellular constituents, including sulphydryls, lipids, amino acids and nucleotides and can cause cell death, lipid peroxidation, carcinogenesis and aging. The aim of this study was to characterize ONOO− scavenging constituents from herbs. Twenty‐eight herbs were screened for their ONOO− scavenging activities with the use of a fluorometric method. The potency of scavenging activity following the addition of authentic ONOO− was in the following order: witch hazel bark > rosemary > jasmine tea > sage > slippery elm > black walnut leaf > Queen Anne's lace > Linden flower. The extracts exhibited dose‐dependent ONOO− scavenging activities. We found that witch hazel (Hamamelis virginiana L.) bark showed the strongest effect for scavenging ONOO− of the 28 herbs. Hamamelitannin, the major active component of witch hazel bark, was shown to have a strong ability to scavenge ONOO−. It is suggested that hamamelitannin might be developed as an effective peroxynitrite scavenger for the prevention of ONOO− involved diseases. Copyright © 2002 John Wiley & Sons, Ltd.
Detection of microbial contamination of packaging for foodstuffs by gas chromatography–mass spectrometry method
Authors: Mielniczuk Zbigniew , Pogorzelska Zofia
Published: October 2002

Detection of microbial contamination of packaging for foodstuffs and of the environment, using a gas chromatography–mass spectrometry (GC–MS) method, is described. Quantitative determination of muramic acid, a chemical marker of bacterial peptidoglycan, has been used for this purpose. Samples of dust collected from packaging material (plastic film in the store‐room), intended to come into contact with foodstuffs, and dust from a laboratory environment were hydrolysed in aqueous hydrochloric acid and next extracted with hexane to remove hydrophobic compounds. The aqueous phase was evaporated, heated in silylation reagent to trimethylsilyl derivatives and analysed by GC–MS. Internal standard (3‐hydroxytridecanoic methyl ester) was added before silylation procedure for quantification purposes. The method described is quick and simple, can be applied to study chemical markers directly without prior culturing, in complex
environmental samples (not only of packaging), and should therefore become widely used for measuring bacterial peptidoglycan. The method can be used for the detection of microbial infection in humans, hospitals, infusing fluids,
contamination of biochemical and fermentation processes, and for
monitoring of air, water, air‐conditioning systems, etc. Copyright © 2002 John Wiley & Sons, Ltd.
Detection of norbolethone, an anabolic steroid never marketed, in athletes' urine
Authors: Catlin Don H. , Ahrens Brian D. , Kucherova Yulia
Published: October 2002

Norbolethone (13‐ethyl‐17‐hydroxy‐18,19‐dinor‐17α‐pregn‐4‐en‐3‐one) is a 19‐nor anabolic steroid first synthesized in 1966. During the 1960s it was administered to humans in efficacy studies concerned with short stature and underweight conditions. It has never been reported by doping control laboratories. Norbolethone was identified in two urine samples from one athlete by matching the mass spectra and chromatographic retention times with those of a reference standard. The samples also contained at least one likely metabolite. The samples were also unusual because the concentrations of endogenous steroids were exceptionally low. Since norbolethone is not known to be marketed by any pharmaceutical company, a clandestine source of norbolethone may exist. Copyright © 2002 John Wiley & Sons, Ltd.
9‐Aminoacridine as a matrix for negative mode matrix‐assisted laser desorption/ionization
Authors: Vermillion‐Salsbury Rachal L. , Hercules David M.
Published: October 2002

9‐Aminoacridine (9AA) is introduced as a matrix for negative mode matrix‐assisted laser desorption/ionization (MALDI). While most traditional MALDI matrices have been acidic in character, 9AA is a moderately strong base. The mechanism by which 9AA brings about ionization in the negative mode appears to involve abstraction of a labile proton in an acid/base reaction. Most MALDI matrices readily donate protons; 9AA readily accepts them leading to the formation of [M − H]− species. 9AA was first examined as a matrix for low molecular weight compounds having acidic protons, such as phenols, carboxylic acids, sulfonates, amines and alcohols. Also studied were larger molecules frequently analyzed by MALDI including oligonucleotides, oligoamides and proteins. Spectra obtained from 9AA were compared with those recorded using more traditional matrices such as 2,5‐dihydroxybenzoic acid (DHB) and α‐cyano‐4‐hydroxycinnamic acid (α‐CHCA). Copyright © 2002 John Wiley & Sons, Ltd.
On the design of fault detection filters with game‐theoretic‐optimal sensitivity
Authors: De Persis C. , Isidori A.
Published: October 2002

The problem of residual generation for fault detection and isolation in the presence of measurement noise for a class of nonlinear systems is considered. Exploiting the tools and the results of the geometric approach to the problem of residual generation, a method is proposed for the design of a filter which attenuates the effect of the measurement noise on the residual in the case in which the effect of the fault on the residual is minimal. Copyright © 2002 John Wiley & Sons, Ltd.
The influence of seasonality and duration of flooding on zooplankton in experimental billabongs
Authors: Nielsen D. L. , Hillman T. J. , Smith F. J. , Shiel R. J.
Published: October 2002

The regulation of Australian lowland rivers such as the River Murray has resulted in changes to the flooding characteristics of many associated wetlands. It has been suggested that these changes in flooding have changed the pattern of response of many wetland biota. The substantial variability in the size and shape of these wetlands makes limited field observations difficult to interpret. To overcome this variability 16 experimental billabongs were constructed in which factors that may cause changes to populations within billabongs could be manipulated. In this paper we report on experiments that test the hypothesis that changing the pattern of flooding alters the density and diversity of rotifers and microcrustaceans in billabongs. The experimental billabongs were sampled fortnightly for two years. During this time four flood events were imposed. Flooding of the experimental billabongs resulted in increased microcrustacean abundance. Rotifer abundance rarely increased following flooding. Changing the time of flooding did not modify this response. Observed changes in community structure following flooding result from changes in the relative densities of taxa already present rather than changes in the community composition. Copyright © 2002 John Wiley & Sons, Ltd.
Efficiency of fish ladders for neotropical ichthyofauna
Authors: Agostinho Angelo Antonio , Gomes Luiz Carlos , Fernandez Domingo Rodriguez , Suzuki Harumi Irene
Published: October 2002

The reproductive strategies of potamodromous fish of the Plata basin involve upstream migration and passive downstream movements of eggs and larvae for dozens of kilometres. At the end of the downstream movements, the fry need marginal lagoons or bays in order for their development to be successful. The construction of reservoirs, often in series, has interrupted the movements, and is perhaps the main factor in the decrease in the abundance of migratory fish in the basin. In an attempt to lessen the impact on the upstream migrations, fish passages (floodgates, elevators and mainly ladders) have been constructed and, despite limitations, they have functioned with relative success. Some studies show the continuity of the migration of individuals captured downstream and released into the reservoir. However, downstream migration of adult migratory species is made difficult by the fact that they are, in this phase, generally reophylic (live in running water) and occupy only the upper stretches of reservoirs (fluvial and transitional zones). It would be feasible only in short reservoirs and with a very short residence time. The fact that reservoirs present calm waters, more transparency and contain a large number of small fish could delay the passive drift of eggs and larvae, exposing them to intense predation and/or promoting their settling toward deeper water, where the conditions of oxygenation are generally critical. In the remote event that the larvae reach the dam, most of them cannot be attracted to ladders (elevators are conceived only for upstream movements) or driven away from the reservoir vicinities, in as much as they have passive movements and would therefore suffer great mortality if they passed through turbines or a spillway. In reservoirs with large free stretches upstream and endowed with ample natural floodplain areas, transposition can be an useful instrument in the maintenance of genetic heterogeneity since the number of transposed specimens does not compromise the stocks of the lower stretch. These limitations, connected to the strategy of neotropical fishes, make fish passages in most situations an inadequate instrument for preservational management. Copyright © 2002 John Wiley & Sons, Ltd.
Bond percolation critical probability bounds for three Archimedean lattices
Authors: Wierman John C.
Published: October 2002

Rigorous bounds for the bond percolation critical probability are determined for three Archimedean lattices: .7385 < pc((3, 122) bond) < .7449, .6430 < pc((4, 6, 12) bond) < .7376, .6281 < pc((4, 82) bond) < .7201. Consequently, the bond percolation critical probability of the (3, 122) lattice is strictly larger than those of the other ten Archimedean lattices. Thus, the (3, 122) bond percolation critical probability is possibly the largest of any vertex‐transitive graph with bond percolation critical probability that is strictly less than one. © 2002 Wiley Periodicals, Inc. Random Struct. Alg., 20: 507–518, 2002
On mixing times for stratified walks on the d‐cube
Authors: Garcia Nancy , Palacios José Luis
Published: October 2002

Using the electric and coupling approaches, we derive a series of results concerning the mixing times for the stratified random walk on the d‐cube, inspired in the results of Chung and Graham (1997) [Random Struct. Alg., 11, 199–122]. © 2002 Wiley Periodicals, Inc. Random Struct. Alg., 20: 540–552, 2002
The decomposition threshold for bipartite graphs with minimum degree one
Authors: Yuster Raphael
Published: October 2002

Let H be a fixed bipartite graph with δ(H) = 1. It is shown that if G is any graph with n vertices and minimum degree at least \documentclass{article}\pagestyle{empty}\begin{document}${n\over 2}\bigl(1 + o_n(1)\bigr)$\end{document} and e(H) divides e(G), then G can be decomposed into e(G)/e(H) edge‐disjoint copies of H. This is best possible and significantly extends the result of an earlier paper by the author [8] which deals with the case where H is a tree. © 2002 Wiley Periodicals, Inc. Random Struct. Alg., 21: 121–134, 2002
Revising and assessing explanatory models in a high school genetics class: A comparison of unsuccessful and successful performance
Authors: Johnson Susan K. , Stewart Jim
Published: October 2002

In this paper we describe the model‐revising problem‐solving strategies of two groups of students (one “successful,” one “unsuccessful”) as they worked (in a genetics course we developed) to revise Mendel's simple dominance model to explain the inheritance of a trait expressed in any of four variations. The two groups described in this paper were chosen with the intent that the strategies that they employed be used to inform the design of model‐based instruction. Differences were found in the groups' abilities to recognize anomalous data, use existing models as templates for revisions, and assess revised models. © 2002 Wiley Periodicals, Inc. Sci Ed 86:463–480, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/sce.10015
Topology‐adaptive modeling of objects using surface evolutions based on 3D mathematical morphology
Authors: Hara Kenji , Zha Hongbin , Hasegawa Tsutomu
Published: October 2002

Level set methods were proposed mainly by mathematicians for constructing a model of a 3D object of arbitrary topology. However, those methods are computationally inefficient due to repeated distance transformations and increased dimensions. In the paper, we propose a new method of modeling fast objects of arbitrary topology by using a surface evolution approach based on mathematical morphology. Given sensor data covering the whole object surface, the method begins with an initial approximation of the object by evolving a closed surface into a model topologically equivalent to the real object. The refined approximation is then performed using energy minimization. The method has been applied in several experiments using range data, and the results are reported in the paper. © 2002 Wiley Periodicals, Inc. Syst Comp Jpn, 33(9): 58–67, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.1152
Implementation and performance evaluation of a FIFO queue class library for time warp
Authors: Hidaka Soichiro , Aoki Terumasa , Aida Hitoshi , Saito Tadao
Published: October 2002

The authors describe the implementation, use, and performance evaluation of a FIFO queue class library by means of high‐performance, easy‐to‐use interface employed for queuing simulations in parallel discrete simulations based on the time warp method. Various general‐purpose simulation libraries and languages have been proposed, and among these some have the advantage of not requiring users to define anything other than the state vector, and not needing awareness of rollback under a platform which performs state control based on copies. However, because the state vectors must be defined as simple data structures without pointers, dynamic data structures such as a FIFO queue cannot be handled directly. Under the proposed class library, both the platform and the user can handle such structures in the same fashion that embedded data structures are handled. In addition, instead of all stored data, just the operational history can be stored and recovered efficiently at an effectively minimal cost by taking advantage of the first‐in–first‐out characteristics of the above data structures. When the kernel deletes past state histories during a simulation, garbage collection is also performed transparently using the corresponding method. © 2002 Wiley Periodicals, Inc. Syst Comp Jpn, 33(9): 90–98, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.1155
Optimal low‐energy SIMS conditions for characterizing ZrO2/Si interfaces
Authors: Jiang Z. X. , Chen S. , Sieloff D.
Published: October 2002

Development of high‐K gate dielectric materials has placed a stringent demand for inspection tools with ultrahigh depth resolving power and detection sensitivity. Low‐energy SIMS is potentially the technique of choice provided that the analytical related artifacts are well understood and efficiently suppressed. In this work we profiled superficial and buried metal–organic chemical vapour deposited ZrO2 films and investigated the artifacts involved in SIMS profiling at various beam conditions. It was demonstrated that O2+ beams at near‐normal incidence yielded extremely broad Zr down‐slopes in Si, an artifact likely due to a pronounced preferential sputtering of Si when the instantaneous surface reached the ZrO2/Si interfaces. Suppression of this artifact can be realized by probing O2+ beams at oblique incidence, favorably at 60° for a 1 keV O2+. Nevertheless, the normal‐incidence O2+ beam remained optimal for characterizing the up‐slope of Zr at the polycrystalline Si (polySi)/ZrO2 interface, owing to the minimized matrix effects and suppressed surface roughness. For profiling a gate stack (polySi/ZrO2/Si) at oblique incidences, the high depth resolution of low‐energy SIMS was hindered by the pronounced roughness in poly‐Si. This can be remedied by ion beam smoothing of the poly‐Si prior to SIMS profiling. Using the optimal SIMS conditions, we profiled poly‐Si/ZrO2/Si wafers with and without dopant activation anneal. The SIMS data revealed significant reactions between ZrO2 and Si upon thermal anneal at 1025°C for 10 s. Copyright © 2002 John Wiley & Sons, Ltd.
Static SIMS analysis of random poly (lactic‐co‐glycolic acid)
Authors: Shard A. G. , Clarke S. , Davies M. C.
Published: October 2002

Random poly(lactic‐co‐glycolic acid) (PLGA) has been studied by XPS and SIMS. It is demonstrated that the mole fraction of lactide units in the copolymer can be determined by analysis of selected ion intensities in the SIMS spectra. The results are in good agreement with XPS data and the SIMS ion yields of the four ions in the (3M–O)·+ series from PLGA are shown to be almost identical. The relative ion intensities in this series closely match the binomial distribution expected from a random copolymer. Copyright © 2002 John Wiley & Sons, Ltd.
Maximum likelihood estimation in the joint analysis of time‐to‐event and multiple longitudinal variables
Authors: Lin Haiqun , McCulloch Charles E. , Mayne Susan T.
Published: October 2002

Joint modelling of longitudinal and survival data has received much attention in recent years. Most have concentrated on a single longitudinal variable. This paper considers joint modelling in the presence of multiple longitudinal variables. We explore direct association of time‐to‐event and multiple longitudinal processes through a frailty model and use a mixed effects model for each of the longitudinal variables. Correlations among the longitudinal variables are induced through correlated random effects. We allow effects of categorical and continuous covariates on both longitudinal and time‐to‐event responses and explore interactions between the longtudinal variables and other covariates on time‐to‐event. Estimates of the parameters are obtained by maximizing the joint likelihood for the longitudinal variable processes and the event process. We use a one‐step‐late EM algorithm to handle the direct dependence of the event process on the modelled longitudinal variables along with the presence of other fixed covariates in both processes. We argue that such a joint analysis with multiple longitudinal variables is advantageous to one with only a single longitudinal variable in revealing interplay among multiple longitudinal variables and the time‐to‐event. Copyright © 2002 John Wiley & Sons, Ltd.
Knowledge inventories and managerial myopia
Authors: Miller Kent D.
Published: October 2002

Managing knowledge inventories is the central issue posed by the knowledge‐based view of the firm. Knowledge inventory management involves acquiring, retaining, deploying, idling, and abandoning technologies. Because of future opportunities to switch technologies over time, managing knowledge inventories requires valuing flexibility. Real option theory presents normative conceptual frameworks and pricing formulas for valuing flexibility. These formulas assume managers consider the full time horizon of technologies as well as all available substituting and complementary technologies. This study considers the implications of violations of these assumptions (i.e., temporal and spatial myopia) for managers' technology investment decisions. Specifying decision criteria under alternative forms of myopia reveals possible sources and patterns of technology management decision errors. This study highlights the cognitive sources of path dependencies and organizational rigidities. Copyright © 2002 John Wiley & Sons, Ltd.
The philosophy of strategy
Authors: Powell Thomas C.
Published: October 2002

The recent increase in philosophy of science articles in strategic management reflects researchers' rising concerns with understanding and securing the field's intellectual foundations. This article argues for a proactive approach to the philosophy of strategy, and for the rejection of conventional, ‘off‐the‐shelf’ philosophies that neither contemplated, nor can assimilate, the epistemological messiness and action‐connectedness of strategic management. The article responds to Rodolphe Durand's critique, revisits the logic of competitive advantage, and makes the case for a pragmatist philosophy of strategy. Copyright © 2002 John Wiley & Sons, Ltd.
Product development strategies for established market pioneers, early followers, and late entrants
Authors: Robinson William T. , Chiang Jeongwen
Published: October 2002

At the time of entry, market pioneers are known for emphasizing major product development projects. After being in the market for many years, however, do market pioneers, early followers, and late entrants maintain different product development strategies? Data from 2273 established manufacturing businesses reveal that market pioneers have the highest probability of engaging in product development, which covers product R&D spending as well as new product sales. Even so, market pioneers and early followers tend to emphasize minor projects, such as product improvements and line extensions. Late entrants are less likely to engage in product development, but those that do tend to emphasize major development efforts. Copyright © 2002 John Wiley & Sons, Ltd.
When do acquirers earn abnormal returns?
Authors: Capron Laurence , Pistre Nathalie
Published: October 2002

In this study, we explore the conditions under which acquirers earn abnormal returns. We provide an empirical test of Barney and Chatterjee's arguments by examining the role of the respective resource contribution of the target and the acquirer. Combining an event study with a survey of postacquisition resource transfer on a sample of 101 horizontal acquisitions, we find that acquirers do not earn abnormal returns when they only receive resources from the target. In this case, it is likely that multiple bidders, which could have equally captured these resources, competed away all the abnormal returns from the successful bidder. In contrast, we find that acquirers can expect to earn abnormal returns when they transfer their own resources to the target. Overall, we find that value creation does not ensure value capture for the acquirer. Copyright © 2002 John Wiley & Sons, Ltd.
Reflections on career development among student affairs leaders
Authors: Blimling Gregory S.
Published: October 2002

This chapter examines the career paths of student affairs leaders and their reflections on the factors that matter most in making important career choices.
Uncommon truths: A diary of practical wisdom
Authors: Blimling Gregory S.
Published: October 2002

The author reflects on unconventional truths that he has learned from over twenty‐five years of student affairs administration.