bluuebunny/crossref_metadata_2025 huggingface dataset:
Relationship between the dynamic softening transition and wet sliding friction of elastomer compounds
Authors: Pan Xiao‐Dong
Published: May 2004

For properly chosen elastomer compounds, thermorheological characterization is combined with an examination of the variation of the wet sliding friction with temperature. A conceptual argument leads to the assumption that the wet sliding friction should maximize at the energy dissipation peak associated with the dynamic softening transition at a characteristic frequency determined by the sliding speed and the effective smallest surface asperity scale. The dynamic softening transition is characterized with the peak in tan δ/G′n, where tan δ is the loss tangent,G′ is the elastic modulus, andnis a constant between 0 and 1. The William–Landel–Ferry transform is uncritically applied for extrapolating the position of the peak in tan δ/G′nat high frequencies. Even based on the criterion of tan δ, the results obtained on a concrete surface indicate that the effective smallest asperity scale is of order of 100 μm. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2467–2478, 2004
Magnetic properties of Ga‐substituted FeGa0.1Cr1.9S4 with inverse spinel structure
Authors: Son Bae Soon , Kim Sam Jin , Kim Chul Sung
Published: May 2004

FeGa0.1Cr1.9S4 has been studied with Mössbauer spectroscopy, X‐ray diffraction, magnetization, and magnetoresistance (MR). The crystal structure is found to be a cubic spinel by Rietveld refinement of X‐ray diffraction. The Mössbauer spectrum of FeGa0.1Cr1.9S4 consists of two doublets at room temperature. The cation distribution is determined by Mössbauer spectroscopy, which reveals that the small amounts of Ga ions occupy tetrahedral sites and FeGa0.1Cr1.9S4 has an inverse spinel type of structure. MR measurement of the sample shows that the metal–semiconductor transition occurs in the temperature range 77–300 K. The gap energies for regions I (T < 150 K) and II (T > 200 K) are 24.1 and 103.8 meV, respectively. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Evaluation of thermal degradation of 2.25Cr–1Mo steel by magnetic Barkhausen noise
Authors: Byeon Jai Won , Kim C. S. , Kwun S. I.
Published: May 2004

An attempt was made to evaluate nondestructively thermally degraded 2.25Cr–1Mo steel by magnetic Barkhausen noise (MBN) technique. Microstructural analysis (mean size of carbides), measurement of mechanical property (hardness) and magnetic Barkhausen noise parameters (rms voltage, count) for a wide range of specimens isothermally degraded at 630 °C were carried out to obtain the correlations between them. Both the rms voltage (MBNrms) and the count (MBNcount) of MBN signal were observed to increase rapidly in the initial 1000 hours of aging time and then slowly thereafter, which was attributed to decreased number of carbides as a result of carbides coarsening during thermal aging. Linear correlations of MBNcount with both the mean size of carbides and the hardness were found. MBNcount was suggested as a promising nondestructive evaluation parameter for assessing the thermally degraded microstructure and mechanical property of the 2.25Cr–1Mo steel. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of Heusler alloy thin film, Cu2MnAl and Co2MnSi, deposited by co‐sputtering method
Authors: Kim Keewon , Kwon Soon‐Ju , Kim Tae‐Wan
Published: May 2004

Thin films of Heusler alloy, Cu2MnAl and Co2MnSi were fabricated successfully, by the co‐sputtering method. Magnetic and structural properties are strongly dependent on substrate temperature. The films fabricated at room temperature show paramagnetic behaviour and amorphous or very fine crystalline feature in XRD and TEM analysis. On increasing substrate temperature, there appear polycrystalline features of L21 structure, accompanied by ferromagnetic properties. Also, the electrical resistivity implies that the electronic structures are heavily disturbed in the films fabricated at room temperature. These results suggest that structural ordering strongly affects the magnetic and electrical properties of Cu2MnAl and Co2MnSi. The Curie temperature and saturation magnetization of Co2MnSi, Cu2MnAl are 950 K (with extrapolation), 1100 emu/cc and 600 K, 440 emu/cc, respectively. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fractal analysis of time‐resolved magnetic domain patterns in Co/Pd multilayer with varying number of repeats
Authors: Kim Dong‐Hyun , Cho Yoon‐Chul , Choe Sug‐Bong , Shin Sung‐Chul
Published: May 2004

We investigate the fractal behavior of magnetic domain together with analysis of dynamic reversal behavior in Co/Pd multilayer films prepared with different number of repeats n. We utilize a novel magneto‐optical microscope magnetometer technique to visualize the time‐resolved domain evolution patterns in these films. Quantitative analysis of the time‐resolved domain evolution patterns allows us to determine the fractal dimension Df and the reversal ratio V/R depending on n, where V/R represents the counterbalance between the wall‐motion speed V and the nucleation rate R. As n increases, domain shape becomes more ragged and complex and thus, Df increases. Interestingly enough, the change in Df clearly seems to be coupled to the change in V/R with varying n, which implies that the correlation between Df and V/R is mediated via the distributed defects. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Oscillations of magnetic parameters and giant magnetization of Fe/Be superlattices
Authors: Stetsenko P. N. , Goryunov G. E. , Kim Chong Oh , Kim Cheol‐Gi , Antipov S. D. , Smirnitskaya G. V. , Krasheninnikov A. P. , Skabitskaya O. V.
Published: May 2004

This research consists of the comprehensive study of structure and thickness dependences of basic magnetic parameters and of hyperfine fields on 57Fe nuclei from room‐temperature Mössbauer absorption spectroscopy of magnetic superlattices (MSL) of Fe with Be spacers synthesized using cathode sputtering in HV‐discharge with oscillating electrons. We report two series of MSL: [Fe(10 Å)/Be(tBe)] and [Fe(tFe)/Be(8 Å)]; in the former, deep oscillations of spontaneous magnetization (Js0) value vs. spacer thickness have been observed with period of 6–8 Å, while in the [Fe(tFe)/Be(8 Å)] series the oscillations do not show up. The observed giant values of Js0 normalized to Fe content (up to 5200 Gs) and the low values of hyperfine fields suggest the necessity of taking into account the orbital contributions to local magnetic moments of Fe atoms in Fe/Be superlattices. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spectroscopic ellipsometric studies of the dielectric function of Cd1−x−yMnxFeyTe single crystals
Authors: Hwang Younghun , Kim Hyekyeong , Um Youngho , Park Hyoyeol
Published: May 2004

Cd1−x−yMnxFeyTe single crystals grown by the vertical Bridgman method have been studied by measuring the complex dielectric function using spectroscopic ellipsometry in the 1.5 ∼ 5.5 eV photon energy range at room temperature. The CP energy parameters of the E0, E1, E1 + Δ1, and E2 structures were determined by fitting the second‐derivative spectra (d2ε/dω2) with a theoretical model, i.e., the standard critical point (SCP) line shapes. The E1, E1 + Δ1, and E2 energies decreased with increasing Fe composition y, which is due to the hybridization effect of the valence and conduction bands in Cd1−xMnxTe with Fe 3d levels. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Improvement of adhesion strength of W–B–N glue layer on Si for magnetic devices
Authors: Lee Chang Woo , Kim Ji Gon
Published: May 2004

The structural and the mechanical properties of tungsten boron nitride (W–B–N) thin films were studied to investigate the effects of boron and nitrogen in W–B–N glue layer. The scratch test show that the adhesion strengths of magnetic films on the WBN glue layers are greatly improved from 9–11 N of W–N glue layer to 26–30 N of W–B–N glue layer. The more adhesive contact can be attributed to the boron and nitrogen interstitials because these boron and nitrogen interstitials are expected to modify the structural and physical properties in the W–B–N films. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetization process and domains in MTJ
Authors: Czapkiewicz M. , Zoladz M. , Wrona J. , Wisniowski P. , Rak R. , Stobiecki T. , Kim C. G. , Kim C. O. , Takahashi M. , Tsunoda M.
Published: May 2004

The magnetization process and domain structure of free layers in as deposited and annealed magnetic tunnel junctions (MTJ) of Si/Ta/Cu/Ta/NiFe/Cu/IrMn(10)/CoFe(2.5)/Al–O(1.5)/CoFe(2.5)/NiFe(t)/Ta, where t = 10, 30 and 100 nm, were investigated by Kerr microscopy, R‐VSM and MOKE magnetometers. Different types of domain patterns observed in free layers (CoFe(2.5)/NiFe(t)) depending on the mutual relation between interlayer coupling energy and free layer magnetostatic energy. For as deposited samples fuzzy domains with fine irregular “patches” pattern, typical for weak interlayer coupling, are observed. Annealed MTJs, however, are characterized by large domains superimposed by crossed stripes, which led to the blocking of coherent rotation of magnetization. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spin‐glass‐like transition in interacting MnFe2O4 nanoparticles
Authors: Balaji G. , Wilde G. , Weissmüller J. , Gajbhiye N. S. , Sankaranarayanan V. K.
Published: May 2004

The temperature dependent of ac susceptibility studies are carried out on interacting 9.0 nm size MnFe2O4 particles in a wide frequency range (10–103 Hz) and in various external applied magnetic fields. At low external fields, the real part of ac susceptibility exhibit a maximum near room temperature. Interestingly, the imaginary part exhibits two maximum, one near 40 K and the other near room temperature. The former is interpreted as due to a spin‐glass‐like transition and the latter to the superparamagnetic blocking of the particles. The frequency dependence analysis of the spin‐glass‐like transition by Arrhenius and Volger–Fulcher laws is found to be unsatisfactory. The dynamic scaling analysis on frequency dependence of spin‐glass‐like transition temperature fits the model of a transition at finite temperature and yields critical exponents and parameters as: zν = 6.0, Tc = 34.4 K, τ0 = 10−7 s and that confirms the occurrence of spin‐glass‐like transition in 9.0 nm MnFe2O4 particles. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fabrication and swimming properties of micro‐machine coated with magnetite prepared by ferrite plating
Authors: Nishimura K. , Sendoh M. , Ishiyama K. , Arai K. I. , Uchida Hironaga , Inoue Mitsuteru
Published: May 2004

By the sterolithography technique and the ferrite plating, we have fabricated a magnetic micro‐machine which coated Fe3O4. The sterolithography technique enables to form the spiral‐shape resinous templates and the ferrite plating enables to coat Fe3O4 uniformly onto these templates from an aqueous solution. The total machine weight is light because a resin of the template body is almost the same density as water. We have verified that the machines swim freely and wirelessly in water by applying a rotational magnetic field. As the machine coated with Fe3O4 has a biocompatibility, there is a possibility of medical micro‐robots which swim in human body for medical operations. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Change in element distributions in FePt films with Ag or Cu additives associated with their crystallographic phase transformation through thermal annealing
Authors: Aimuta K. , Nishimura K. , Uchida H. , Inoue M.
Published: May 2004

In order to decrease the ordering temperature to the L10 structure of FePt alloy thin films, we have investigated the effect of additional third elements of Au and Cu into FePt films. The ordering temperature for the films has been reduced to 400 °C from 500 °C by adding Ag of 3 at% of or Cu of 7 at%. Analyzing by Auger electron spectroscopy, it was found that Ag moves to the surface in the film with the annealing process. It was considered that the movement could cause the decrement of the ordering temperature. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hopping Al atom on Si(111) 7 × 7 surface studied by scanning tunneling microscopy
Authors: Uchida H. , Kuroda T. , Mohamad Fariza B. , Kim J. , Kashiwagi K. , Nishimura K. , Inoue M.
Published: May 2004

Adsorption of Al atoms on the Si(111) 7 × 7 surface was investigated by STM at room temperature. The adsorbed Al atom displaced a Si center adatom on the surface, and the expelled Si atom diffused inside a half unit cell. The adsorbed Al atom hopped among center adatom sites with a frequency of about 0.01s−1. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bioactive brominated diterpenes from the marine red alga Jania Rubens (L.) Lamx.
Authors: Awad Nagwa E.
Published: May 2004

Seven brominated diterpenes of the parguerene and isoparguerene series were isolated for the ﬁrst time from the red alga Jania rubens (L.) Lamx., collected from the Red Sea coast at Hurghada, Egypt. The diterpenes were identiﬁed as isoparguerol (1), isoparguerol‐16‐acetate (2), isoparguerol‐7,16‐diacetate (3), parguerol‐16‐acetate (4), parguerol‐7,16‐diacetate (5), deoxyparguerol (6) and deoxyparguerol‐7‐acetate (7).

The isolated diterpenes had a marked antitumour activity. Isoparguerol derivatives were slightly more effective than parguerol derivatives. Moreover, the data implied that the cytotoxicity of these compounds were dependent on the number of acetoxy groups. Also, anthelmintic activities of the isolated compounds on earthworms (Allolobophora caliginosa) were studied. Copyright © 2004 John Wiley & Sons, Ltd.
Hepatoprotective effect of Sabina przewalskii against menadione‐induced toxicity
Authors: Ip Siu‐Po , Woo Ka‐Yan , Lau Oi‐Wah , Che Chun‐Tao
Published: May 2004

Sabina przewalskii is a Tibetan medicinal plant. Pretreatment with an ethyl acetate‐soluble fraction of the plant suppressed the plasma alanine aminotransferase activity in menadione‐intoxicated mice. In vitro studies showed that the Sabina extract could inhibit NADH‐induced superoxide production in isolated hepatocytes as indicated by a decrease of lucigenin‐ampliﬁed chemiluminescence. In addition, the extract inhibited tert‐butyl hydroperoxide‐induced lipid peroxidation in isolated hepatocytes dose‐dependently. These results suggested that the protective action of the Sabina extract against menadione‐induced hepatotoxicity is associated with its antioxidant activities including the scavenging of superoxide anion radicals and inhibition of lipid peroxidation. Copyright © 2004 John Wiley & Sons, Ltd.
Protective effects of selected medicinal plants against protein degradation, lipid peroxidation and deformability loss of oxidatively stressed human erythrocytes
Authors: Suboh S. M. , Bilto Y. Y. , Aburjai T. A.
Published: May 2004

The effects of seven medicinal plants including Artemisia herba‐alba, Ferula hermonis, Hibiscus sabdariffa, Nigella sativa, Teucrium polium, Trigonella foenum‐graecum, and Allium sativum on protein degradation, lipid peroxidation, erythrocyte deformability and osmotic fragility of erythrocytes exposed in vitro to 10 mM H2O2 for 60 min at 37 °C have been examined. Preincubation of erythrocytes with Nigella sativa and Allium sativum protected erythrocytes against protein degradation, loss of deformability and increased osmotic fragility caused by H2O2, while the other plants failed to protect erythrocytes against these damages. Artemisia herba‐alba did not protect erythrocytes against lipid peroxidation, while Trigonella foenum‐graecum unexpectedly increased lipid peroxidation of erythrocytes exposed to H2O2. Ferula hermonis, Hibiscus sabdariffa, Nigella sativa, Teucrium polium and Allium sativum protected erythrocytes against lipid peroxidation. The results indicate the importance of oxidatively damaged cellular proteins in compromising the rheologic behaviour of the erythrocytes, and that the medicinal plants which have anti‐protein‐oxidant activity (e.g. Nigella sativa and Allium sativum) could be rheologically useful, particularly in pathological conditions related to free radicals. Copyright © 2004 John Wiley & Sons, Ltd.
Ultrastructural changes in the testis and epididymis of rats following treatment with the benzene chromatographic fraction of the chloroform extract of the seeds of Carica papaya
Authors: Manivannan B. , Mishra P. K. , Pathak N. , Sriram S. , Bhande S. S. , Panneerdoss S. , Lohiya N. K.
Published: May 2004

The benzene chromatographic fraction of the chloroform extract of the seeds of Carica papaya at a dose of 10 mg/rat/day for 150 days, which has shown a total inhibition of motility, reduced sperm count and infertility, was tested to deﬁne the mode of action at the subcellular level in the testis and epididymis. The ultrastructure of the testis of the treated animals revealed no appreciable changes in the subcellular characteristics. The mechanism of protein synthesis as well as steroidogenesis were evident in the Sertoli cells while the spermatogonia, spermatocytes and spermatids, both round and elongated, depicted a prominent nucleus, distinct nuclear membrane and cytoplasmic characteristics indicating normal germ cell differentiation. The principal cells of the cauda epididymis were characterized by the presence of well‐deﬁned rough endoplasmic reticulum, mitochondria, Golgi bodies and secretary granules, suggesting active secretory functions. The absorptive function of the cauda epididymis was evidenced by the presence of numerous vesicles and multivesicular bodies adjacent to stereocilia. It is concluded that the inhibition of sperm motility by the drug could be due to other epididymal factors rather than the subcellular characteristics of testis and epididymis. Copyright © 2004 John Wiley & Sons, Ltd.
Neuropharmacological proﬁle of hydroalcohol extract of Valeriana edulis ssp. procera roots in mice
Authors: Oliva Iván , González‐Trujano Ma. Eva , Arrieta Jesús , Enciso‐Rodríguez Roberto , Navarrete Andrés
Published: May 2004

Valerian is the common name given to the crude drug consisting of the underground organs of the species Valeriana. Valeriana edulis ssp. procera Meyer is the Mexican valerian. The aim of the present work was to elucidate the neuropharmacological proﬁle of a hydroalcohol extract of Valeriana edulis roots at doses of 100, 300 and 1000 mg/kg in several experimental models. A dose‐dependent anticonvulsant and anxiolytic‐like effect of V. edulis was demonstrated. In addition, the extract decreased rotarod performance and traction force and prolonged the pentobarbital‐induced sleeping time at high doses. Concomitant administration of valerian extract and pentobarbital showed a synergistic effect on motor coordination and traction force in mice. The anxiolytic‐like effect of V. edulis was compared with diazepam and with diphenhydramine and doxylamine, the latter in order to consider the H1‐antihistamine effect as another possibility to explain, at least in part, the central nervous system depressant effect of valerian. These results also underlie the medical and industrial use of this species and allowed the conclusion that the extract of V. edulis has central nervous depressant properties similar to, but with some differences to V. ofﬁcinalis, a very well known species. Copyright © 2004 John Wiley & Sons, Ltd.
Kava treatment in patients with anxiety
Authors: Geier F. P. , Konstantinowicz T.
Published: May 2004

In several clinical trials, mainly conducted with a dose of 300 mg kava extract per day, kava has been employed successfully for the treatment of anxiety disorders.

The goal of the placebo‐controlled double‐blind outpatient trial was to obtain more information on the dosage range and efﬁcacy of a kava special extract WS 1490 in patients with non‐psychotic anxiety. 50 patients were treated with a daily dose of 3 × 50 mg WS 1490 during a 4‐week treatment period followed by a 2‐week safety observation phase.

In the active treatment group, the total score of the Hamilton anxiety scale (primary efﬁcacy variable), showed a therapeutically relevant reduction in anxiety versus placebo (more than 4 points). In the secondary variables studied, HAMA ‘somatic and psychic anxiety’ subscales, the Erlangen anxiety, tension and aggression scale (EAAS), the brief personality structure scale (KEPS), the adjective checklist (EWL 60‐S) and clinical global impressions scale (CGI), a trend in favour of the active treatment was detectable. WS 1490 was well tolerated and showed a safety proﬁle with no drug‐related adverse events or post‐study withdrawal symptoms.

It can be concluded that the applied 150 mg WS 1490 per day is an effective and safe treatment of non‐psychotic anxiety syndromes in the described population. Copyright © 2004 John Wiley & Sons, Ltd.
Ferulic acid alleviates lipid peroxidation in diabetic rats
Authors: Balasubashini M. Sri , Rukkumani R. , Viswanathan P. , Menon Venugopal P.
Published: May 2004

Diabetes mellitus is a metabolic disorder associated with increased formation of free radicals. The objective of our study was to determine whether ferulic acid (FA), a phenolic acid, has any role to play in diabetes induced free radical formation. Diabetes was induced with streptozotocin. The levels of blood glucose, thiobarbituric acid reactive substances (TBARS), hydroperoxides and free fatty acids (FFA) increased in the liver of diabetic animals. The activities of glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase (CAT) decreased in the liver. Histopathology of pancreas also shows shrunken islets. Supplementation of FA to the diabetic rats resulted in a decrease in the levels of glucose, TBARS, hydroperoxides, FFA and an increase in reduced glutathione (GSH). FA also resulted in increased activities of SOD, CAT, GPx and expansion of pancreatic islets. The effect was much pronounced with lower dose treatment. Thus our study shows that administration of ferulic acid helps in enhancing the antioxidant capacity of these diabetic animals by neutralizing the free radicals formed thereby reducing the intensity of diabetes. Copyright © 2004 John Wiley & Sons, Ltd.
Butyryl‐ and acetyl‐cholinesterase inhibitory activities in essential oils of Salvia species and their constituents
Authors: Savelev Sergey U. , Okello Edward J. , Perry Elaine K.
Published: May 2004

Extracts of Salvia (sage) species have been reported to have cholinergic activities relevant to the treatment of Alzheimer's disease. A lack of information on the inhibition of the enzyme butyrylcholinesterase, also considered to be a target in the treatment of the disease, prompted this in vitro investigation of the essential oils of S. fruticosa, S. lavandulaefolia, S. ofﬁcinalis and S. ofﬁcinalis var. purpurea for anti‐butyrylcholinesterase activity.

Dose‐dependent inhibition of human cholinesterases by the extracts and constituents was determined using the method of Ellman. A time dependent increase in the inhibition of butyrylcholinesterase by the oils of S. fruticosa and S. ofﬁcinalis var. purpurea was evident. IC50 values decreased from 0.15 ± 0.007 and 0.14 ± 0.007 mg/mL after 5 min to 0.035 ± 0.016 and 0.06 ± 0.018 mg/mL after 90 min incubation time respectively. The slow onset of inhibition of butyrylcholinesterase was also shown by individual constituents, such as 3‐carene and β‐pinene. Analyses of the chemical composition of the oils and anti‐butyrylcholinesterase activity of their constituents revealed that none of the compounds tested would account for the total activity of the oils and that synergy is likely. Copyright © 2004 John Wiley & Sons, Ltd.
Protective effect of water yam (Dioscorea alata L.) extract on the copper‐driven fenton reaction and X‐ray induced DNA damage in vitro
Authors: Wang Tsu‐Shing , Liang Shih‐Jyue , Lii Chong‐Kuei , Liu Sin‐Yie
Published: May 2004

The rhizome extract of Dioscorea has been shown to possess radical scavenging activity. In this study, the protective effect of water yam (Dioscorea alata L.) rhizome extract on calf thymus DNA and plasmid DNA strand breakage by the copper‐driven Fenton reaction and X‐irradiation was examined. The protective activity in vitro of four lyophilized extracts obtained from yam rhizomes: (1) aqueous extract (YAE); (2) 30% ethanolic extract (YEE); (3) aqueous extract boiled for 30 min (BYAE); and (4) 30% ethanolic extract boiled for 30 min (BYEE) were evaluated by ethidium bromide binding assay and DNA nicking assay. The YAE, YEE, and BYEE effectively inhibited the copper‐driven Fenton reaction‐induced damage of calf thymus DNA, while inhibition was less pronounced in the case of X‐ray induced strand breakage of plasmid DNA. While BYAE potently inhibited X‐ray induced strand breaks in plasmid pGL3 DNA, it failed to inhibit, and even greatly enhanced copper‐H2O2 induced damage of calf thymus DNA. The present results demonstrate strong copper chelating and weak hydroxyl radical scavenging activities in yam rhizome extracts, and these activities may vary depending on the procedures used in preparing the extract. Copyright © 2004 John Wiley & Sons, Ltd.
Magnetic interactions in nonalternant mixed molecular radical crystals and mixed ion radical crystals
Authors: Minkov I. , Tadjer A.
Published: May 2004

The character and the magnitude of magnetic interaction in 1‐D stacks of mixed molecular radical crystals (MMRCs) and mixed molecular ion radical crystals (MMIRCs) of alternant aromatic hydrocarbons have already been studied theoretically. In this work nonalternant 1‐D stacks built of π‐electronic subunits are considered. Some of the elementary units are singly or doubly charged (MMIRCs), others are neutral (MMRCs); alternant and nonalternant subunits are used as building blocks. Qualitative investigations based on the band theory of exchange effects in solid organic open‐shell systems are carried out. The contributions to the effective exchange integral Jeff: direct (Hund's), kinetic and indirect, are calculated. Structures of 1:1 MMRCs and MMIRCs with positive value of the integral Jeff, accounting for the spin exchange of the electrons in the half‐filled band, i.e., with ferromagnetic ground state, are suggested. The influence of different parameters (molecular size, presence of heteroatoms, localization versus delocalization, alternant versus nonalternant, charge, etc.) on the magnitude of the net exchange is discussed. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Confidence intervals for the effect of a prognostic factor after selection of an ‘optimal’ cutpoint
Authors: Holländer Norbert , Sauerbrei Willi , Schumacher Martin
Published: May 2004

When investigating the effects of potential prognostic or risk factors that have been measured on a quantitative scale, values of these factors are often categorized into two groups. Sometimes an ‘optimal’ cutpoint is chosen that gives the best separation in terms of a two‐sample test statistic. It is well known that this approach leads to a serious inflation of the type I error and to an overestimation of the effect of the prognostic or risk factor in absolute terms. In this paper, we illustrate that the resulting confidence intervals are similarly affected. We show that the application of a shrinkage procedure to correct for bias, together with bootstrap resampling for estimating the variance, yields confidence intervals for the effect of a potential prognostic or risk factor with the desired coverage. Copyright © 2004 John Wiley & Sons, Ltd.
Controlling the risk of spurious findings from meta‐regression
Authors: Higgins Julian P. T. , Thompson Simon G.
Published: May 2004

Meta‐regression has become a commonly used tool for investigating whether study characteristics may explain heterogeneity of results among studies in a systematic review. However, such explorations of heterogeneity are prone to misleading false‐positive results. It is unclear how many covariates can reliably be investigated, and how this might depend on the number of studies, the extent of the heterogeneity and the relative weights awarded to the different studies. Our objectives in this paper are two‐fold. First, we use simulation to investigate the type I error rate of meta‐regression in various situations. Second, we propose a permutation test approach for assessing the true statistical significance of an observed meta‐regression finding. Standard meta‐regression methods suffer from substantially inflated false‐positive rates when heterogeneity is present, when there are few studies and when there are many covariates. These are typical of situations in which meta‐regressions are routinely employed. We demonstrate in particular that fixed effect meta‐regression is likely to produce seriously misleading results in the presence of heterogeneity. The permutation test appropriately tempers the statistical significance of meta‐regression findings. We recommend its use before a statistically significant relationship is claimed from a standard meta‐regression analysis. Copyright © 2004 John Wiley & Sons, Ltd.
A simple approach to power and sample size calculations in logistic regression and Cox regression models
Authors: Væth Michael , Skovlund Eva
Published: May 2004

For a given regression problem it is possible to identify a suitably defined equivalent two‐sample problem such that the power or sample size obtained for the two‐sample problem also applies to the regression problem. For a standard linear regression model the equivalent two‐sample problem is easily identified, but for generalized linear models and for Cox regression models the situation is more complicated. An approximately equivalent two‐sample problem may, however, also be identified here. In particular, we show that for logistic regression and Cox regression models the equivalent two‐sample problem is obtained by selecting two equally sized samples for which the parameters differ by a value equal to the slope times twice the standard deviation of the independent variable and further requiring that the overall expected number of events is unchanged. In a simulation study we examine the validity of this approach to power calculations in logistic regression and Cox regression models. Several different covariate distributions are considered for selected values of the overall response probability and a range of alternatives. For the Cox regression model we consider both constant and non‐constant hazard rates. The results show that in general the approach is remarkably accurate even in relatively small samples. Some discrepancies are, however, found in small samples with few events and a highly skewed covariate distribution. Comparison with results based on alternative methods for logistic regression models with a single continuous covariate indicates that the proposed method is at least as good as its competitors. The method is easy to implement and therefore provides a simple way to extend the range of problems that can be covered by the usual formulas for power and sample size determination. Copyright © 2004 John Wiley & Sons, Ltd.
Controlling test case explosion in test generation from B formal models
Authors: Legeard Bruno , Peureux Fabien , Utting Mark
Published: May 2004

BZ‐TESTING‐TOOLS (BZ‐TT) is a tool set for automated test case generation from B and Z specifications. BZ‐TT uses boundary and cause–effect testing on the basis of the formal model. It has been used and validated on several industrial applications in the domain of critical software, particularly smart card and transport systems. This paper presents the test coverage criteria supported by BZ‐TT. On the one hand, these correspond to various classical structural coverage criteria, but specialized to the case of B abstract machines. The paper gives algorithms for these in Prolog. On the other hand, BZ‐TT introduces new coverage criteria for complex data structures, based on boundary analysis: this paper defines weak and strong state‐boundary coverage, input‐boundary coverage and output‐boundary coverage. Finally, the paper describes how BZ‐TT presents a unified view of these criteria to the validation engineer, and allows him or her to control the test case explosion on a coarse basis (choosing from a range of coverage criteria) as well as a fine basis (selecting options for each state or input variable). Copyright © 2004 John Wiley & Sons, Ltd.
Decision Making with Uncertain Information: Learning from Women in a High Risk Breast Cancer Clinic
Authors: Frost Caren J. , Venne Vickie , Cunningham Dianne , Gerritsen‐McKane Ruth
Published: May 2004

Patients and practitioners may believe that clinically validated laboratory tests provide definitive information. Genetic counselors know this is not always so, and the possibility of inconclusive genetic test results is often discussed in the pretest counseling session. This added discussion topic prolongs the process of genetic counseling, but if there is inadequate patient understanding, patient frustration may be high when receiving a result of uncertain significance, and patients may make decisions about subsequent medical management based on incorrect assumptions. For patients/participants in a research setting, where the clinical validity of testing may be unclear, some patients/participants may still want to use test results to influence their medical management. This paper presents findings from a qualitative study wherein 15 women from the High Risk Breast Cancer Clinic at Utah's Huntsman Cancer Institute discussed how uncertainty regarding results affected their decision making. The women were randomly selected from 3 categories—women with test results of uncertain significance; women without cancer who have a mutation; and women who are members of high‐risk families, but for whom no mutation was found. Study findings will be used in future studies to better understand how to improve communication regarding uncertain results, especially in a research environment.
Detailed kinematics, structure and recurrence of micro‐seismicity in the SAFOD target region
Authors: Nadeau Robert M. , Michelini Alberto , Uhrhammer Robert A. , Dolenc David , McEvilly Thomas V.
Published: May 2004

Large numbers of small earthquakes recorded over 2 decades and analyzed with advanced techniques are used to characterize the detailed kinematics, structure and recurrence interval scaling properties of micro‐seismicity in a 4 × 4 km lateral and 6 km deep crustal volume encompassing the region of the SAFOD deep drilling experiment. The characterization reveals that the seismically active San Andreas fault in the vicinity of SAFOD's repeating magnitude 2 target earthquakes is composed of two sub‐parallel fault strands that are creeping at comparable rates and that one of the strands lies between the SAFOD drilling platform and SAFOD's target events. In the region, ∼55% of the earthquakes are members of 52 characteristically repeating earthquake sequences. The recurrence intervals of the repeating target events are consistent with the interval scaling of the other sequences. However this scaling is contrary to that expected from standard constant stress‐drop theory.
Diurnal cycle of convection, clouds, and water vapor in the tropical upper troposphere: Satellites versus a general circulation model
Authors: Tian Baijun , Soden Brian J. , Wu Xiangqian
Published: May 2004

Global high‐resolution (3‐hourly, 0.1° × 0.1° longitude‐latitude) water vapor (6.7 μm) and window (11 μm) radiances from multiple geostationary satellites are used to document the diurnal cycle of upper tropospheric relative humidity (UTH) and its relationship to deep convection and high clouds in the whole tropics and to evaluate the ability of the new Geophysical Fluid Dynamics Laboratory (GFDL) global atmosphere and land model (AM2/LM2) to simulate these diurnal variations. Similar to the diurnal cycle of deep convection and high clouds, coherent diurnal variations in UTH are also observed over the deep convective regions, where the daily mean UTH is high. In addition, the diurnal cycle in UTH also features a land‐sea contrast: stronger over land but weaker over ocean. UTH tends to peak around midnight over ocean in contrast to 0300 LST over land. Furthermore, UTH is observed to lag high cloud cover by ∼6 hours, and the latter further lags deep convection, implying that deep convection serves to moisten the upper troposphere through the evaporation of the cirrus anvil clouds generated by deep convection. Compared to the satellite observations, AM2/LM2 can roughly capture the diurnal phases of deep convection, high cloud cover, and UTH over land; however, the magnitudes are noticeably weaker in the model. Over the oceans the AM2/LM2 has difficulty in simulating both the diurnal phase and amplitude of these quantities. These results reveal some important deficiencies in the model's convection and cloud parameterization schemes and suggest the lack of a diurnal cycle in SST may be a shortcoming in the boundary forcing for atmospheric models.
Acid‐sulfate weathering of synthetic Martian basalt: The acid fog model revisited
Authors: Tosca Nicholas J. , McLennan Scott M. , Lindsley Donald H. , Schoonen Martin A. A.
Published: May 2004

The acid fog model has received considerable attention as a model of soil formation on Mars. Previous evaluations of this model have focused on experimental weathering of terrestrial basalt samples. However, these samples differ significantly from what now is thought to be typical of Martian basalt. The acid fog model is tested here using synthetic basaltic analogs derived from Mars Pathfinder soil and rock compositions. Reaction of synthetic basalt with various acidic solutions and subsequent evaporation has led to the formation of several putative secondary mineral phases. Many of these phases were not produced in prior experimental studies aimed at aqueous interactions on Mars. Of these alteration phases, Mg, Fe, Ca, and Al sulfates were identified. In addition, secondary ferric oxide phases formed via rapid Fe oxidation under relatively high pH levels buffered by basalt dissolution. Amorphous silica is a ubiquitous product in these experiments and has formed by precipitation from solution and by the dissolution of minerals and glasses leaving behind leached surface layers composed of residual silica. The secondary products formed in these experiments demonstrate the importance of primary mineralogy when testing models of aqueous interactions on Mars. New constraints are placed on both the reactivity of primary basalt and the secondary mineralogy present at the Martian surface.
Interpretation of concentration‐discharge patterns in acid‐neutralizing capacity during storm flow in three small, forested catchments in Shenandoah National Park, Virginia
Authors: Rice Karen C. , Chanat Jeffrey G. , Hornberger George M. , Webb James R.
Published: May 2004

Episodic concentration‐discharge (c‐Q) plots are a popular tool for interpreting the hydrochemical response of small, forested catchments. Application of the method involves assuming an underlying conceptual model of runoff processes and comparing observed c‐Q looping patterns with those predicted by the model. We analyzed and interpreted c‐Q plots of acid‐neutralizing capacity (ANC) for 133 storms collected over a 7‐year period from three catchments in Shenandoah National Park, Virginia. Because of their underlying lithologies the catchments represent a gradient in both hydrologic and geochemical behavior, ranging from a flashy, acidic, poorly buffered catchment to a moderate, neutral, well‐buffered catchment. The relative frequency of observed anticlockwise c‐Q loops in each catchment decreased along this gradient. Discriminant function analysis indicated that prestorm base flow ANC was an important predictor of loop rotation direction; however, the strength of the predictive relationship decreased along the same gradient. The trends were consistent with several equally plausible three‐component mixing models. Uncertainty regarding end‐member timing and relative volume and possible time variation in end‐member concentrations were key factors precluding identification of a unique model. The inconclusive results obtained on this large data set suggest that identification of underlying runoff mechanisms on the basis of a small number of c‐Q plots without additional supporting evidence is likely to be misleading.
Interpreting the temperature of water at cold springs and the importance of gravitational potential energy
Authors: Manga Michael , Kirchner James W.
Published: May 2004

Circulating groundwater transports heat. If groundwater flow velocities are sufficiently high, most of the subsurface heat transport can occur by advection. This is the case, for example, in the Cascades volcanic arc where much of the background geothermal heat is transported advectively and then discharged when the groundwater emerges at springs. The temperature of spring water can thus be used to infer the geothermal heat flux. If spring water temperature is many degrees warmer than the ambient temperature, as it is at hot springs, determining the heat discharged at springs is straightforward. At large‐volume cold springs, however, the geothermal warming of water is small because the added heat is diluted in a large volume of water. We show that in order to interpret the temperature of cold springs we must account for three processes: (1) conversion of gravitational potential energy to heat through viscous dissipation, (2) conduction of heat to or from the Earth's surface, and (3) geothermal warming. Using spring temperature data from the central Oregon Cascades and Mount Shasta, California, we show that the warming due to surface heat exchange and dissipation of gravitational potential energy can be comparable to that due to geothermal heating. Unless these confounding sources of heating are taken into account, estimates of geothermal heat flux derived from temperatures of cold springs can be incorrect by large factors.
Conditions necessary for capillary hysteresis in porous media: Tests of grain size and surface tension influences
Authors: Tokunaga Tetsu K. , Olson Keith R. , Wan Jiamin
Published: May 2004

Hysteresis in the relation between water saturation and matric potential is generally regarded as a basic aspect of unsaturated porous media. However, the nature of an upper length scale limit for saturation hysteresis has not been previously addressed. Since hysteresis depends on whether or not capillary rise occurs at the grain scale, this criterion was used to predict required combinations of grain size, surface tension, fluid‐fluid density differences, and acceleration in monodisperse systems. The Haines number (Ha), composed of the aforementioned variables, is proposed as a dimensionless number useful for separating hysteretic (Ha < 15) versus nonhysteretic (Ha > 15) behavior. Vanishing of hysteresis was predicted to occur for grain sizes greater than 10.4 ± 0.5 mm, for water‐air systems under the acceleration of ordinary gravity, based on Miller‐Miller scaling and Haines' original model for hysteresis. Disappearance of hysteresis was tested through measurements of drainage and wetting curves of sands and gravels and occurs between grain sizes of 10 and 14 mm (standard conditions). The influence of surface tension was tested through measurements of moisture retention in 7 mm gravel, without and with a surfactant (sodium dodecylbenzenesulfonate (SDBS)). The ordinary water system (Ha = 7) exhibited hysteresis, while the SDBS system (Ha = 18) did not. The experiments completed in this study indicate that hysteresis in moisture retention relations has an upper limit at Ha = 16 ± 2 and show that hysteresis is not a fundamental feature of unsaturated porous media.
Forest biomass estimation over regional scales using multisource data
Authors: Baccini A. , Friedl M. A. , Woodcock C. E. , Warbington R.
Published: May 2004

A combination of statistical models and multisource data were used to map above‐ground forest biomass for National Forest lands in California. To do this, data from the Moderate Resolution Imaging Spectoradiometer were used in combination with precipitation, temperature, and elevation data. The results show that coarse resolution remotely sensed data in combination with relevant topographic and climate data can be used to map above‐ground biomass with good accuracy over large areas. For the data sets considered, empirical models based on a 2 percent sample explained 73 percent of the variance in biomass in the remaining 98 percent of the data with a root mean square error of 44.4 tons/ha. These results suggest that it should be feasible to improve estimates of above‐ground carbon stocks at regional to continental scales in the near future.
Gossip as Cultural Learning
Authors: Baumeister Roy F. , Zhang Liqing , Vohs Kathleen D.
Published: May 2004

To complement views of gossip as essentially a means of gaining information about individuals, cementing social bonds, and engaging in indirect aggression, the authors propose that gossip serves to help people learn about how to live in their cultural society. Gossip anecdotes communicate rules in narrative form, such as by describing how someone else came to grief by violating social norms. Gossip is thus an extension of observational learning, allowing one to learn from the triumphs and misadventures of people beyond one's immediate perceptual sphere. This perspective helps to explain some empirical findings about gossip, such as that gossip is not always derogatory and that people sometimes gossip about strangers.
A Social Comparison Account of Gossip
Authors: Wert Sarah R. , Salovey Peter
Published: May 2004

The central thesis of this article is that all gossip involves social comparison. Research on social comparison is applied toward understanding motivations for gossip. In addition, the authors address why gossip tends to be negative and make predictions about factors that trigger especially negative talk about others. Factors such as need for moral information, powerlessness, formation and maintenance of in-groups and out-groups, and situations that bring on perceptions of injustice or feelings of jealousy, envy, and resentment all contribute to malicious gossip. Finally, the morality of gossip is considered, especially as it relates to the misuse or overuse of social comparison. Gossip is purposeful and, perhaps, necessary for healthy social functioning.
Introduction to the Special Issue on Gossip
Authors: Wert Sarah R. , Salovey Peter
Published: May 2004

This article represents the introduction to a special issue of the Review of General Psychology on gossip. All of the articles in this special issue argue that gossip is purposeful and important to social functioning.
Research on Gossip: Taxonomy, Methods, and Future Directions
Authors: Foster Eric K.
Published: May 2004

A half century of gossip research from multiple disciplines is reviewed. Discussed are definitions of the construct; social, evolutionary, and personal functions of the practice; and data collection methods. Though people engage in the practice frequently, there has been relatively little psychological research on gossip. The layperson's understanding of the term is included in, but insufficient to encompass, definitions used by researchers. Most data are ethnographic and discursive, and few parametric data exist. The area could benefit from better experimental methods and instruments. Neurobiological and social network analysis methods are promising foundations for further study. There are real-world implications for understanding gossip. Strengthening gossip theory and research methods will beneficially inform the way we view the practice in context.