bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fabrication and characterization of GaN‐based LEDs grown on nanopatterned sapphire substrates
Authors: Gao Haiyong , Yan Fawang , Zhang Yang , Li Jinmin , Zeng Yiping , Wang Guohong 
Published: June 2008

AbstractSapphire substrates were nanopatterned by dry (inductively coupled plasma, ICP) etching to improve the performance of GaN‐based light‐emitting diodes (LEDs). GaN‐based LEDs on nanopatterned sapphire substrates (NPSS) were fabricated by metal organic chemical vapor deposition (MOCVD). The characteristics of LEDs fabricated on NPSS prepared by dry etching were studied. The light output power and wall‐plug efficiency of the LEDs fabricated on NPSS were greater than those of the conventional LEDs fabricated on common planar sapphire substrates when the injection currents were the same. The LEDs on NPSS and common planar sapphire substrates have similar I –V characteristics. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Micromagnetic structures of nanocrystalline ferromagnetic materials – comparison of simulation and experiment
Authors: Saranu S. , Grob A. , Weissmüller J. , Herr U. 
Published: June 2008

AbstractThe micromagnetic structure of nanocrystalline ferromagnetic materials is characterized by local fluctuations induced by the randomly varying magnetocrystalline anisotropy of the individual grains. Micromagnetic simulations may improve the understanding of the relevant features and the interpretation of the experimental observations of the magnetic structure. In this study we investigate the magnetic structure of nanocrystalline FeSi and Co model systems with average grain sizes of 20 nm to 60 nm. Small angle neutron scattering (SANS) is a suitable technique to study the micromagnetic structures of nanocrystalline materials at the nanometer scale. The simulated SANS curves for the FeSi model systems are compared with the experimental SANS curves of Vitroperm samples. It is found that the scattering at high fields is dominated by the local anisotropy fluctuations which can be well reproduced by the simulations. The simulations of the nanocrystalline hcp Co show that the stray fields resulting from the local magnetic fluctuations should lead to an observable contrast in magnetic force microscopy (MFM) images. We show that the contrast observed in the real MFM images of thin nanocrystalline hcp Co films compares well with the simulated image contrast with respect to magnitude and length scale of the observed fluctuations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the magnetism of the σ‐phase Fe–Cr alloys
Authors: Cies’︁lak J. , Reissner M. , Steiner W. , Dubiel S. M. 
Published: June 2008

AbstractMagnetic properties of microcrystalline σ‐Fe100–x Crx (45 ≤ x ≤ 50) alloys were investigated with Mössbauer‐effect and magnetization measurements performed as a function of temperature and external magnetic field up to 15 T. The Curie temperature, TC, and the average magnetic moment per Fe atom, 〈μ 〉, which were determined, decrease linearly with x; the former at the rate of ∼7 K/at% and the latter at the rate of 0.033 μB/at%. The 〈μ 〉‐values determined are significantly larger than those in the literature. The characteristic features of the magnetization curves are that they (a) do not saturate even at 15 T, and (b) show bending approximately up to 3 times the derived TC values. The relationship between the average hyperfine field and 〈μ 〉 was revealed to be non‐linear. The latter, non‐saturating character of isothermal magnetization curves and Rhodes‐Wohlfarth plot are in favour of the itinerant model of magnetism in the investigated samples. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of oxygen partial pressure on optical and electrical properties of co‐sputtered amorphous zinc indium tin oxide thin films
Authors: Saji K. J. , Jayaraj M. K. 
Published: June 2008

AbstractTransparent thin films of amorphous zinc indium tin oxide were prepared at room temperature by co‐sputtering of zinc oxide and indium tin oxide. Effect of oxygen partial pressure on the optical and electrical properties of amorphous zinc indium tin oxide thin films were investigated. Conductivity, carrier concentration and Hall mobility showed strong dependence on the oxygen partial pressure and these parameters decreased with the increase of oxygen pressure. The effect of subgap states caused a sharp difference in measured optical band gap values between the films deposited with and without oxygen partial pressure. Carrier transport studies were carried out by temperature dependent conductivity measurements. At low electron density, the conductivity showed thermally activated behaviour and at higher carrier concentrations it changed to almost degenerate band conduction. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Compensation effect of Sn in PbI2 polycrystalline layers
Authors: Ponpon J. P. , Mousa A. M. , Amann M. 
Published: June 2008

AbstractTin has been introduced into polycrystalline lead iodide during solution growth of thin films. Electrical characterization (current vs. voltage measurements as a function of the temperature and thermally stimulated current experiments) demonstrates that tin introduces a deep donor level in the PbI2 bandgap and compensates the native acceptor defects of lead iodide. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of excess Sb on crystallization of δ‐phase SbTe binary thin films
Authors: Youm Min Soo , Kim Yong Tae , Kim Young Hwan , Sung Man Young 
Published: June 2008

AbstractThe phase‐change temperature and crystal structures of the δ‐phase SbTe alloy for Sb contents of 64 at%, 72 at%, and 76 at% have been investigated. The δ‐phase SbTe alloy has a rhombohedral crystal structure, and crystallization occurs in an extremely narrow temperature range of 140–145 °C compared with Sb40Te60. We have determined the relationship between the Sb content and the crystalline structure using X‐ray diffraction and selected area electron diffraction. When the Sb content increases, the number of Sb layers stacked with Sb2Te3 in the unit cell increases, which results in the lowering of the activation energy for crystallization and a lower ovonic threshold voltage. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of the milling conditions on the formation of nanostructured Fe–Co powders
Authors: Alleg Safia , Bentayeb Fatima Zohra , Bensalem Rachid , Djebbari Chafia , Bessais Lotfi , Greneche Jean Marc 
Published: June 2008

AbstractNanostructured Fe–12Co (wt%) powders were prepared by mechanical alloying in a planetary ball mill. The milling process was carried out at different milling conditions. The obtained powders were characterized by X‐ray diffraction, 57Fe Mössbauer spectrometry and magnetic measurements. The low and high speed ball‐milling conditions lead to the formation of a single and two‐bcc Fe(Co) structure, respectively, having different crystallite sizes, microstrains hyperfine parameters and magnetic properties. The average hyperfine magnetic field values: 〈B〉1 = 34.8 T and 〈B〉2 = 28.2 T of the two‐bcc Fe(Co) structure could be attributed to the nanocrystalline grains and to the grain boundaries, respectively. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determination of carrier effective mass, impurity energy levels, and compensation ratio in Ga4Se3S layered crystals by Hall effect measurements
Authors: Qasrawi A. F. , Gasanly N. M. 
Published: June 2008

AbstractIn this work, the dark electrical resistivity, charge carriers density and Hall mobility of Ga4Se3S single crystals have been measured and analyzed in the temperature region of 200–350 K. The data analyses have shown that this crystal exhibits an extrinsic n‐type of conduction. The temperature‐dependent dark electrical resistivity analysis reflected the existence of energy level as 0.31 eV. The temperature dependence of carrier density was analyzed by using the single donor‐single acceptor model. The latter analysis allowed the determination of electron effective mass as 0.38m0, hole effective mass as 0.42m0, donor impurity energy level as 0.45 eV, acceptor–donor concentration ratio (Na/Nd) as 0.97 and a donor–acceptor concentration difference as Nd – Na = 1.5 × 1011 cm–3. The Hall mobility of Ga4Se3S is found to increase with decreasing temperature following a power law of slope of ∼(–6.3). The abnormal behavior of mobility was attributed to the domination of phonon scattering and/or crystals anisotropy. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A simplified water temperature model for the Colorado River below Glen Canyon Dam
Authors: Wright Scott A. , Anderson Craig R. , Voichick Nicholas 
Published: June 2008

AbstractGlen Canyon Dam, located on the Colorado River in northern Arizona, has affected the physical, biological and cultural resources of the river downstream in Grand Canyon. One of the impacts to the downstream physical environment that has important implications for the aquatic ecosystem is the transformation of the thermal regime from highly variable seasonally to relatively constant year‐round, owing to hypolimnetic releases from the upstream reservoir, Lake Powell. Because of the perceived impacts on the downstream aquatic ecosystem and native fish communities, the Glen Canyon Dam Adaptive Management Program has considered modifications to flow releases and release temperatures designed to increase downstream temperatures. Here, we present a new model of monthly average water temperatures below Glen Canyon Dam designed for first‐order, relatively simple evaluation of various alternative dam operations. The model is based on a simplified heat‐exchange equation, and model parameters are estimated empirically. The model predicts monthly average temperatures at locations up to 421 km downstream from the dam with average absolute errors less than 0.5°C for the dataset considered. The modelling approach used here may also prove useful for other systems, particularly below large dams where release temperatures are substantially out of equilibrium with meteorological conditions. We also present some examples of how the model can be used to evaluate scenarios for the operation of Glen Canyon Dam. Published in 2008 by John Wiley & Sons, Ltd.
Optimum treatment allocation rules under a variance heterogeneity model
Authors: Wong Weng Kee , Zhu Wei 
Published: June 2008

AbstractWe provide optimal treatment allocation schemes when the outcome variance varies across the treatment groups and our objectives are to estimate treatment effects with equal or unequal interest. Unlike other optimal designs, such asA‐optimal designs, the proposed designs can be found without an iterative scheme. We evaluate robustness properties of the optimal designs to mis‐specification in the expected variance from each group and identify situations when popular allocation schemes have poor efficiencies. An application to design a randomized rheumatoid arthritis trial is discussed, along with a potential application to design a cancer screening trial when the main outcome is a continuous variable. Copyright © 2008 John Wiley & Sons, Ltd.
Dose–schedule finding in phase I/II clinical trials using a Bayesian isotonic transformation
Authors: Li Yisheng , Bekele B. Nebiyou , Ji Yuan , Cook John D. 
Published: June 2008

AbstractA dose–schedule‐finding trial is a new type of oncology trial in which investigators aim to find a combination of dose and treatment schedule that has a large probability of efficacy yet a relatively small probability of toxicity. We demonstrate that a major difference between traditional dose‐finding and dose–schedule‐finding trials is that while the toxicity probabilities follow a simple nondecreasing order in dose‐finding trials, those of dose–schedule‐finding trials may adhere to a matrix order. We show that the success of a dose–schedule‐finding method requires careful statistical modeling and a sensible dose–schedule allocation scheme. We propose a Bayesian hierarchical model that jointly models the unordered probabilities of toxicity and efficacy and apply a Bayesian isotonic transformation to the posterior samples of the toxicity probabilities, so that the transformed posterior samples adhere to the matrix‐order constraints. On the basis of the joint posterior distribution of the order‐constrained toxicity probabilities and the unordered efficacy probabilities, we develop a dose–schedule‐finding algorithm that sequentially allocates patients to the best dose–schedule combination under certain criteria. We illustrate our methodology through its application to a clinical trial in leukemia and compare it with two alternative approaches. Copyright © 2008 John Wiley & Sons, Ltd.
Atomic Force Microscopy‐Derived Nanoscale Chip for the Detection of Human Pathogenic Viruses
Authors: Artelsmair Helga , Kienberger Ferry , Tinazli Ali , Schlapak Robert , Zhu Rong , Preiner Johannes , Wruss Juergen , Kastner Markus , Saucedo‐Zeni Nadia , Hoelzl Martin , Rankl Christian , Baumgartner Werner , Howorka Stefan , Blaas Dieter , Gruber Hermann J. , Tampé Robert , Hinterdorfer Peter 
Published: June 2008

AbstractNative‐protein nanolithography (NPNL) was used to fabricate stable bioactive arrays of viral receptor spots. The arrays were specific for the cognate virus and devoid of nonspecific protein and virus adsorption under physiologic conditions. The spot size ranged from 200 nm × 200 nm to 2 µm × 2 µm and up to 3 × 3 spots were arranged per array. With proper force adjustment in the patterning experiments, His6‐tagged bovine serum albumin (BSA) molecules were selectively removed from the underlying self‐assembled monolayer (SAM) while leaving the latter intact. Injection of His6‐tagged very low density lipoprotein receptor (VLDLR‐His6) constructs resulted in specific, oriented binding to the Ni2+‐loaded bis‐(nitrolotriacetic acid) (bis‐NTA) groups to the re‐exposed SAM areas. The arrays of viral receptors were used for the detection of human rhinovirus particles (serotype 2; HRV2) under native conditions by topographical imaging at high signal‐to‐noise ratio. The kinetic on‐rate of the HRV2‐VLDLR interaction was derived from the time‐dependent binding of the virions to the VLDL receptor spots. No significant binding was observed for the major group virus HRV14 that uses the unrelated receptor ICAM‐1.
Bioavailability of chemical pollutants in contaminated soils and pitfalls of chemical analyses in hazard assessment
Authors: Vasseur P. , Bonnard M. , Palais F. , Eom I. C. , Morel J. L. 
Published: June 2008

AbstractDecision‐making for remediation of industrial wastelands are still based on the concentrations of pollutants of concern measured in soils. In this work, two soils polluted by polycyclic aromatic hydrocarbons (PAHs) and metals were investigated for their toxicity on earthworms (Eisenia fetida), collembolae (Folsomia candida), and higher plants (Brassica chinensis, Lactucca sativa and Avena sativa) in order to study the relationships between chemical contamination and biological effects. Although the level of contamination by PAHs was elevated and commensurate in the two soils, their toxicity profile was quite different. Soil A affected survival and reproduction of invertebrates and growth of higher plants. Surprisingly, soil B, heavily contaminated by metals in addition to PAHs, was devoid of toxicity. Our results indicate that toxicity cannot simply be extrapolated from pollutant concentrations in a complex matrix in which bioavailability of pollutants may be reduced by ageing. Moreover, the use of toxicity data obtained from spiked soils characterized by readily bioavailable pollutants can also be called into question for such extrapolations. Predicting biological effects therefore requires biological tools to avoid any erroneous conclusions that can be drawn from sole extrapolation of analytical results. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2008.
Distribution of oil‐degrading bacteria in coastal seawater, Toyama Bay, Japan
Authors: Tanaka Daisuke , Tanaka Shunsuke , Yamashiro Yoko , Nakamura Shogo 
Published: June 2008

AbstractOil‐degrading bacteria are considered to play an important role in the biodegradation of spilled or released oil in the sea. The distribution of indigenous oil‐degrading bacteria in the coastal seawater of Toyama Bay, Japan, was examined. Surface seawater samples with or without oil film in fishing port were analyzed by denaturing gradient gel electrophoresis (DGGE) of the PCR‐amplified V3 region of bacterial 16S rDNA. Sequence analysis revealed that several DGGE bands clearly detected only in samples with oil film corresponded to Cyanobacteria. Moreover, we cultured surface seawater samples with oil film in two different liquid culture media, a marine broth and an NSW medium; each culture contained 0.5% (w/v) C‐heavy oil. Emulsification of the oil was observed at day 6 in the marine broth and day 9 in the NSW medium. Time‐dependent changes of bacterial communities in those culture media were analyzed by DGGE. Interestingly, we found that Alcanivorax sp. became one of the dominant bacteria in each culture medium when emulsification of the oil began. Alcanivorax sp. is one of the well‐known oil‐degrading bacteria in seawater and is associated with the production of biosurfactants. These results suggest that Cyanobacteria and Alcanivorax play important roles in the bioremediation of oil‐contaminated areas in Toyama Bay. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2008.
Assessment of mixture toxicity of copper, cadmium, and phenanthrenequinone to the marine bacterium Vibrio fischeri
Authors: Wang Wenxi , Lampi Mark A. , Huang Xiao‐Dong , Gerhardt Karen , Dixon D. George , Greenberg Bruce M. 
Published: June 2008

AbstractTransition metals and polycyclic aromatic hydrocarbons (PAHs) are cocontaminants at many sites. Contaminants in mixtures are known to interact with biological systems in ways that can greatly alter the toxicity of individual compounds. The toxicities (individually and as mixtures) of copper (Cu), a redox‐active metal; cadmium (Cd), a nonredox active metal; and phenanthrenequinone (PHQ), a redox‐active oxygenated PAH, were examined using the bioluminescent bacterium Vibrio
fischeri. We found that the cotoxicity of Cu/PHQ was dependent on the ratio of concentrations of each chemical in the mixture. Different interaction types (synergism, antagonism, and additivity) were observed with different combinations of these toxicants. The interaction types changed from antagonism at a low Cu to PHQ ratio (1:4), to additive at an intermediate Cu to PHQ ratio (2:3), to synergistic at higher Cu to PHQ ratios (3:2 and 4:1). In contrast to Cu/PHQ mixtures, the cotoxicity of Cd/PHQ did not change at different mixture ratios and was found for the most part to be additive. For the individual chemicals and their mixtures, reactive oxygen species (ROS) production was observed in V. fischeri, suggesting that individual and mixture toxicity of Cu, Cd, and PHQ to V. fischeri involves ROS‐related mechanisms. This study shows that mixture ratios can alter individual chemical toxicity, and should be taken into account in risk assessment. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2009.
Effects of methyl parathion exposure on development and reproduction in the viviparous fish Girardinichthys multiradiatus
Authors: Arellano‐Aguilar Omar , Macías Garcia Constantino 
Published: June 2008

AbstractMethyl parathion (MeP), an insecticide commonly used in Mexico, has been detected in water bodies adjacent to agricultural crops and is accumulated in the tissue of the amarillo (Girardinichthys multiradiatus), a viviparous fish unique to Central Mexico. Evidence of MeP accumulation in a G. multiradiatus population prompted assessment of the consequences of exposure to MeP during the gestation period and adult life. We exposed adult fish to MeP in the diet at concentrations ranging from 0.001 to 0.165 μg/g dry weight of food. Fish accumulated MeP at concentrations from 0.21 to 5.87 μg/g of fish and exhibited a significant reduction in weight and growth rate. We also evaluated the effects on broods of pregnant females exposed to 0.005, 0.01, and 0.1 μg/g dry weight of food. Although these pregnant females were not affected, their offspring showed an increase in spinal cord malformation and a reduction in survival to adulthood. Finally, we sampled seven localities inhabited by G. multiradiatus; this revealed the presence of MeP in two water bodies at concentrations of 0.0036 and 0.037 μg/mL respectively. Our results suggest that low MeP concentrations affect immature fish with possible consequences later in life. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2009.
In situ evaluation of sediment toxicity in Guadalete Estuary (SW Spain) after exposure of caged Arenicola marina
Authors: Ramos‐Gómez Julia , Martín‐Díaz M. Laura , Rodríguez Araceli , Riba Inmaculada , DelValls T. Ángel 
Published: June 2008

AbstractA 7 day in situ assay to assess sediment toxicity was carried out per replicate in two sites from Guadalete Estuary (Guad1 and Guad2) (South‐West, Spain) using the polychaete Arenicola marina (n = 20) in benthic cages. After the exposure period, a battery of biomarkers were determined to asses the sediment toxicity. Five of them were exposure biomarkers [ethoxyresorufin O‐deethylase (EROD), dibenzylfluorescein (DBF) dependant CytP450, gluthation reductase (GR), and gluthation‐S‐transferase (GST) activities] and one of them was an effect biomarker [lipid peroxidation (LPO)]. Toxicity due to metals bound to the sediment was found in Guad2. Metals provoke the inhibition of EROD, DBF, and GR and the induction of GST, which is showed to carry out antioxidative stress defense. Toxicity caused by metals and also PAH was detected in Guad1. The presence of these chemicals leads to GST induction in and presumably in consequence, to LPO inhibition. GST activity resulted to be the main protection mechanism against oxidative stress in Arenicola marina. We suggest further research in Guadalete Estuary focusing on the detection and toxicity assessment of pharmaceutical and personal care products. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2008.
In vivo genotoxic potential of microcystin‐LR: A cyanobacterial toxin, investigated both by the unscheduled DNA synthesis (UDS) and the comet assays after intravenous administration
Authors: Gaudin Julien , Le Hegarat Ludovic , Nesslany Fabrice , Marzin Daniel , Fessard Valérie 
Published: June 2008

AbstractMicrocystin‐LR (MC‐LR) is a toxin produced by freshwater cyanobacteria and is a potential threat to human health. MC‐LR has been shown to be both a specific inhibitor of serine/threonine protein phosphatases PP1 and PP2A and a potent tumor promoter in rat liver. However, the genotoxic potential of MCs remains unclear. In this article, we investigated the ability of MC‐LR to induce DNA damage on rat hepatocytes following intravenous (iv) administration by using two in vivo genotoxicity assays: the unscheduled DNA synthesis (UDS) and the comet assays. The UDS assay measures DNA synthesis induced from the excision repair of DNA damaged regions and the comet assay is a very sensitive technique for detecting various forms of DNA damage. After an exposure time of 2–4 h or 12–16 h and a dose ranging from 12.5 to 50 μg/kg bw, no DNA damage could be observed in both assays on rat hepatocytes following iv administration. These findings have been discussed and compared with recently published genotoxic results obtained in other organs from mice after oral and intraperitoneal treatments to better understand the mechanism of action of this toxin in relation with its cancerogenicity potential. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2009.