bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of solvent quality on successive solution fractionation (SSF) efficiency of high‐density polyethylene
Authors: Stéphenne Vincent , Bailly Christian , Berghmans Hugo , Daoust Daniel , Godard Pierre 
Published: January 2009

AbstractBACKGROUND: Preparative successive solution fractionation (SSF) is a powerful technique for obtaining narrow‐dispersity fractions on a multi‐gram scale of high‐density polyethylene (HDPE). In a previous paper, the operative separation mechanisms during SSF of a broad HDPE in cyclohexanone were studied. Two mechanisms, and not only one as expected from the literature, contribute to the separation of HDPE molecules according to their molar mass (MM). The very low MM chains are separated by a solid–liquid (S–L) mechanism, while the longer chains are isolated by a liquid–liquid (L–L) phase separation. In the present paper, the influence of a poorer solvent, diphenyl ether, is reported.RESULTS: It is shown that the relative importance of the S–L mechanism with respect to the L–L one is altered by the use of this solvent. The L–L temperature range is increased in diphenyl ether while the S–L transition temperature remains unchanged. Consequently, the SSF efficiency is improved. Large amounts (on a gram scale) of narrow‐dispersity fractions are isolated, mainly by the L–L mechanism. Polydispersities are about 1.5 (compared to 2.0 for cyclohexanone) and a broader MM range of closer molar mass distribution fractions is available.CONCLUSION: This work demonstrates that the use of diphenyl ether, a poorer solvent than cyclohexanone (always used as SSF solvent for polyethylene in the literature), leads to an improvement of SSF efficiency for an essentially linear HDPE. The differences of behaviour during the separation with cyclohexanone or diphenyl ether are explained by the establishment of a phase diagram. Copyright © 2009 Society of Chemical Industry
Fluorine‐ and siloxane‐containing polymers for supercritical carbon dioxide lithography
Authors: Sha Jing , Ober Christopher K 
Published: January 2009

AbstractSupercritical carbon dioxide has emerged as an environmentally friendly solvent for processing selected polymer and molecular glass photoresists at very high resolution. This article describes recent successes in the lithographic patterning of fluorine‐ and siloxane‐containing polymers using supercritical carbon dioxide as a developer solvent. Copyright © 2009 Society of Chemical Industry
The synthesis of organometallic rod–coil block copolymers from polysilanes
Authors: Hiorns Roger C , Holder Simon J 
Published: January 2009

AbstractThis mini‐review gives a short summery of the chain‐end chemistry of polysilanes, notably that leading to block copolymers. The anionic polymerisations of cyclotetrasilanes or ‘masked’ disilenes naturally lend themselves to the formation of polysilane‐containing copolymers. A more robust, if less controlled, method results from the Wurtz‐type reductive coupling reaction that yields polysilanes with silyl chloride chain‐ends which are extremely sensitive to nucleophilic substitution. These may be used with appropriately functionalised polymers (such as polyisoprene or poly(ethylene oxide)) to prepare multiblock copolymers, or with functionalised groups designed as initiating centres for subsequent controlled reversible deactivation radical polymerisations (such as atom transfer radical polymerisation). Copyright © 2009 Society of Chemical Industry
Genetic and biochemical analysis of a laboratory‐selected spirodiclofen‐resistant strain of Tetranychus urticae Koch (Acari: Tetranychidae)
Authors: Van Pottelberge Steven , Van Leeuwen Thomas , Khajehali Jahangir , Tirry Luc 
Published: January 2009

AbstractBACKGROUND: Spirodiclofen is a selective, non‐systemic acaricide from the new chemical class of tetronic acid derivatives. In order to develop strategies to minimise resistance in the field, a laboratory‐selected spirodiclofen‐resistant strain of the two‐spotted spider mite, Tetranychus urticae Koch, was used to determine genetic, toxicological, biochemical and cross‐resistance data.RESULTS: Selecting for spirodiclofen resistance in the laboratory yielded a strain (SR‐VP) with a resistance ratio of 274, determined on the larval stage. The egg stage remained far more susceptible. No cross‐resistance was found against other established acaricides, except for spiromesifen. Based on synergist experiments and enzyme assays, it appeared that especially P450 monooxygenases, but also esterases and glutathione‐S‐transferases, could be involved in the metabolic detoxification of spirodiclofen. Genetic analysis showed that the resistance is inherited as an intermediate trait under control of more than one gene.CONCLUSIONS: Resistance to spirodiclofen exceeded by far the recommended field rate. A good acaricide resistance management programme is necessary to prevent fast resistance build‐up in the field. Spirodiclofen can be used in alternation with most established acaricides, except for other tetronic acid derivatives. Without selection pressure, resistance tends to be unstable and can decrease in the presence of susceptible individuals owing to the intermediate, polygenic inheritance mode. Copyright © 2009 Society of Chemical Industry
Detection of ppm‐order hydrogen gas by Pd/AlGaN/GaN high electron mobility transistor‐based sensors
Authors: Nakamura Seiji , Takahashi Noriyuki , Okumura Tsugunori 
Published: January 2009

AbstractThe hydrogen sensing properties of AlGaN/GaN high electron mobility transistors with Pd gate electrodes are demonstrated under various hydrogen concentrations. Remarkable current variation, as high as 1.7 mA at the drain‐source voltage of 4 V and gate‐source voltage of 0 V, was observed at 140 °C even at 1 part per million (ppm) hydrogen concentration. The logarithmic relation between the detection current variation and the hydrogen concentration was observed. By using the least‐square fit to the experimental data, the reliable lower detection value of hydrogen concentration for the present device can be estimated to be about 0.45 ppm, i.e., 450 parts per billion (ppb) as a current variation of 1 mA. In addition, the turn‐on and turn‐off transient times have been estimated to be approximately 23 and 33 seconds at 160 °C, respectively, in the case of the 100 ppm hydrogen gas. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Status of high efficiency and high power ThinGaN®‐LED development
Authors: Baur Johannes , Baumann Frank , Peter Matthias , Engl Karl , Zehnder Ulrich , Off Juergen , Kuemmler Volker , Kirsch Markus , Strauss Joerg , Wirth Ralph , Streubel Klaus , Hahn Berthold 
Published: January 2009

AbstractIn this paper we report on the improvement of ThinGaN®‐PowerLED structures in epitaxy, chip design, phosphor efficiency and package design. The brightness of these devices increased by a factor of 4 over the last 4 years. We demonstrate 604 mW blue (440 nm; 3,24 V; 53% WPE), 129 lm cool‐white light (5000 K; 3,25 V, 113 lm/W) and 88.2 lm warm‐white (3200 K; 74.4 lm/W; CRI 80) emission for 1mm2‐chip Dragon power LEDs at 350 mA operation. In an advanced device we realized values of 643 mW blue (440 nm; 3,24 V; 350 mA; WPE: 57%) and 155 lm white (5000 K, 350 mA, 3,24 V, 136 lm/W) emission. To our knowledge these are the highest brightness and efficacy values reported in literature. Also at 1.4 A operation current the performance of these multi quantum well epitaxy based structures is superior to the values reported for double heterostructure epitaxy based structures. By combination of phosphor converted white and red 1 mm2 chip LEDs we realized a 3000 K warm white emitting device with 100 lm/W, CRI 90 and 850 lm emission. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electrical properties of Mg‐doped GaN and AlxGa1–xN
Authors: Komissarova Tatiana A. , Jmerik Valentin N. , Mizerov Andrey M. , Shmidt Nataliya M. , Ber Boris Ya. , Kasantsev Dmitry Yu. , Ivanov Sergey V. 
Published: January 2009

AbstractWe report on plasma‐assisted molecular beam epitaxy (PA MBE) growth of Mg‐doped GaN and AlxGa1–xN (x = 0.15 and 0.42) layers on c‐sapphire (N‐polarity) and studies of their electrical properties as functions of growth temperature, Mg flux and alloy composition. P‐type conductivity was examined to follow the general trends defined for MOVPE and Ga‐polar GaN layers grown by metal‐organic vapor phase epitaxy and MBE. The achieved hole concentration in the GaN:Mg layers measured by Hall effect and C‐V is in the range of (0.3 – 2)×1018 cm–3 at Mg BEP changing within (2 – 7)×10–9 Torr. Hall hole concentration p = 4×1017 cm–3 and mobility μ = 1.4 cm2/Vs at 250 K have been measured for the first time in AlxGa1–xN with x > 0.4 grown by PA MBE. Acceptor activation energies for GaN:Mg and Al0.15Ga0.85N:Mg epilayers were determined from temperature dependences of resistivity at T ≥ 300 K to be EA ∼ 100 meV and 220 meV, respectively. Hopping mechanism of conductivity was confirmed for AlxGa1–xN:Mg layers studied at T ≤ 300 K. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effective heat dissipation and higher light extraction efficiency of GaN vertical light emitting diodes for solid state lighting applications
Authors: Chu Chen‐Fu , Fan Feng‐Hsu , Cheng Chao‐Chen , Liu Wen‐Huan , Chu Jiunn‐Yi , Cheng Hao‐Chun , Lin Chia‐Feng , Chen Kuei‐Ting , Tran Chuong Anh , Doan Trung 
Published: January 2009

AbstractVertical sapphire‐free GaN based LEDs (VLEDs) on metal have shown much better performance and prove to deliver an efficiency much higher than most conventional light source. In this paper we show that in addition to many advantages of VLEDs over conventional LEDs in terms of better current spreading, low operation voltage, higher drive current density, faster heat dissipation, VLEDs also enables top surface engineering for efficient light extraction to further light output. High power white LED having efficiency of 110 lumen/watt was achieved through a combination of surface engineering and optimization of the n‐GaN layer thickness underneath the corrugated pyramids surface. The low operation junction temperature of VLEDs demonstrates excellent heat dissipation capabilities. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Studies towards freestanding GaN in hydride vapor phase epitaxy by in‐situ etching of a sacrificial ZnO buffer layer
Authors: Lipskil Frank , Thapa Sarad B. , Hertkorn Joachim , Wunderer Thomas , Schwaiger Stephan , Scholz Ferdinand , Feneberg Martin , Wiedenmann Michael , Thonke Klaus , Hochmuth Holger , Lorenz Michael , Grundmann Marius 
Published: January 2009

AbstractBy in‐situ etching of a ZnO buffer layer freestanding GaN layers were prepared by hydride vapor phase epitaxy (HVPE). For the template growth, single crystalline ZnO buffer layers, grown by pulsed laser deposition on sapphire, were used. They were overgrown with a thin GaN layer by a multilayer growth using metal organic vapor phase epitaxy (MOVPE).The removal of the ZnO buffer during the HVPE growth allowed the fabrication of strain‐free freestanding GaNlayers with a full width‐half‐maximum of the donor bound exciton (D0X) of 2.3 meV at a position of 3.47 eV in low temperature (15 K) photoluminescence (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Vacancy defects probed with positron annihilation spectroscopy in In‐polar InN grown by plasma‐assisted molecular beam epitaxy: Effects of growth conditions
Authors: Reurings Floris , Tuomisto Filip , Gallinat Chad S. , Koblmüller Gregor , Speck James S. 
Published: January 2009

AbstractIn this work we have applied positron annihilation spectroscopy to study the effect of different growth conditions, on vacancy formation in In‐polar InN grown by plasma‐assisted molecular beam epitaxy (PA‐MBE). We find that the stoichiometric conditions have little effect on the In vacancy concentration in the thin films. On the other hand, the optimization of the GaN buffer used for initiating InN growth leads to a lower In vacancy concentration. This indicates that the structural quality of the material dictates the In vacancy formation in InN, while the thermodynamic and kinetic effects have a less important role, contrary to what is observed in, e.g., GaN. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Extremely high efficiency 280 nm‐band emission from quaternary InAlGaN quantum wells realized by controlling Si‐doped layers
Authors: Fujikawa Sachie , Hirayama Hideki , Takano Takayoshi , Tsubaki Kenji 
Published: January 2009

AbstractQuaternary InAlGaN alloys are attracting much attention as candidate materials for realizing deep ultraviolet (DUV) light‐emitting diodes (LEDs). In this study, we investigated the effect of Si‐doping in the quaternary InAlGaN quantum well (QW) emitting region for obtaining a high efficiency DUV emission. Quaternary InAlGaN multi (M)‐QWs with Si‐doped InAlGaN buffer and barrier layers were grown on sapphire (0001) / AlN / AlGaN template by low‐pressure metal‐organic chemical‐vapor deposition (LP‐MOCVD). We found that the surface roughness of InAlGaN layer was significantly improved by introducing the light‐doping of Si. The oxygen impurity concentration in the quaternary InAlGaN layer was significantly reduced by the small amount of Si‐doping. We also revealed that the emission efficiency of the InAlGaN QW was markedly improved by inserting thin (3‐nm‐thick) undoped InAlGaN interlayer between n‐AlGaN buffer and n‐InAlGaN layers. At last, we demonstrated extremely high intensity PL emission from 280 nm‐band InAlGaN QWs at room temperature (RT). The ratio of the integrated intensity of the RT‐PL against the 77 K‐PL was 86%. This result suggests that the internal quantum efficiency (IQE) of the InAlGaN‐QW is considerably high. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
1‐2 ML thick InN‐based quantum wells with InGaN barriers for blue‐green light emitters
Authors: Yuki Akihiko , Watanabe Hiroshi , Che Song‐Bek , Ishitani Yoshihiro , Yoshikawa Akihiko 
Published: January 2009

AbstractAn LED structure with a 1‐2 monolayer (ML) thick InN quantum well (QW) with InGaN barrier grown by radio‐frequency plasma assisted molecular beam epitaxy (rf‐MBE) is proposed for a new active layer of blue‐green light emitters. Compared with previously reported 1‐2 ML thick InN/GaN QWs, extended emission wavelength up to pure green region (∼530 nm) is expected for these QWs with InGaN barriers. It is found that for the InN/InGaN QW structure, in which the InGaN layer is used as a barrier instead of GaN, very thin InN well layers are basically formed in the same manner as the InN/GaN QWs. In photoluminescence spectra at 15 K, emission peak wavelengths are observed from 412 nm to 480 nm when In contents in InGaN barriers are changed from 0.005 to 0.14. The emission wavelength is longer than that of 1‐2ML thick InN/GaN QWs (380nm‐430nm), and green emission can be obtained by further increase of In content in InGaN barrier to more than 0.2. The 1‐2 ML thick InN/In0.08Ga0.92N(10nm) 5‐QW LED structure was successfully fabricated and bright EL emission was observed at 419 nm, which is longer than that of a 1‐2 ML InN/GaN 5‐QW LED. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Astragalus membranaceus prevents daunorubicin‐induced apoptosis of cultured neonatal cardiomyocytes: role of free radical effect of Astragalus membranaceus on daunorubicin cardiotoxicity
Authors: Luo ZhongGuang , Zhong Lu , Han XiaoFeng , Wang HaiRong , Zhong JiHua , Xuan ZhengHua 
Published: January 2009

AbstractAnthracyclines are antitumor antibiotics with significant activity against solid and hematologic malignancies. One problem preventing more widespread use has been the development of cardiotoxicity. To determine whether antioxidant agents can reduce the cardiotoxicity of anthracyclines, a herb Astragalus membranaceus was introduced, which has been widely used for the treatment of cardiovascular diseases in China and was confirmed to be an effective antioxidant agent recently. Pre‐treatment with Astragalus membranaceus significantly attenuated the daunorubicin‐induced increases of reactive oxygen species (p < 0.001), apoptosis (p < 0.05) and the secretions of LDH (p < 0.01) in cultured neonatal cardiomyocytes. Astragalus membranaceus also raised the EC50 of daunorubicin 1.24‐fold. Compared with Astragalus membranaceus, N‐acetyl‐l‐cysteine had similar effects on daunorubicin‐induced cell injury, however, superoxide dismutase reduced reactive oxygen species without attenuating apoptosis. The subcellular distribution of DNR was similar to the distribution of MitoTracker Red 580 in mitochondria, which was mainly in the cytoplasm around the nuclear membrane in cultured neonatal cardiomyocytes. In conclusion, the results suggested that Astragalus membranaceus is potentially protective against daunorubicin cardiotoxicity by decreasing free radical release and apoptosis in cultured neonatal cardiomyocytes. The main subcellular distribution of daunorubicin may be in the mitochondria. Copyright © 2009 John Wiley & Sons, Ltd.
Richardson–Lucy deconvolution of reflection electron energy loss spectra
Authors: Hummel Stefan , Gross Alexander , Werner Wolfgang S. M. 
Published: January 2009

AbstractA procedure for deconvolving the energy spread introduced by the primary beam and the analyzer in a reflection electron energy loss spectrum (REELS) has been developed. The procedure is based on the Richardson–Lucy (RL) algorithm. The approach has been successfully tested on experimental spectra by comparison with spectra with an inherent high‐energy resolution. As a typical result, it was found that the effective energy resolution of spectra with a full width half maximum (FWHM) of the elastic peak of ∼1.5 eV in the raw experimental data can be reduced to ∼0.7 eV in the deconvoluted spectra. Copyright © 2009 John Wiley & Sons, Ltd.
A new estimate of family disease history providing improved prediction of disease risks
Authors: Feng Rui , McClure Leslie A. , Tiwari Hemant K. , Howard George 
Published: January 2009

AbstractComplex diseases often aggregate within families and using the history of family members' disease can potentially increase the accuracy of the risk assessment and allow clinicians to better target on high risk individuals. However, available family risk scores do not reflect the age of disease onset, gender and family structures simultaneously. In this paper, we propose an alternative approach for a family risk score, the stratified log‐rank family score (SLFS), which incorporates the age of disease onset of family members, gender differences and the relationship among family members. Via simulation, we demonstrate that the new SLFS is more closely associated with the true family risk for the disease and more robust to family sizes than two existing methods. We apply our proposed method and the two existing methods to a study of stroke and heart disease. The results show that assessing family history can improve the prediction of disease risks and the SLFS has strongest positive associations with both myocardial infarction and stroke. Copyright © 2009 John Wiley & Sons, Ltd.
Diversification strategy, capital structure, and the Asian financial crisis (1997–1998): evidence from Singapore firms
Authors: Ngah‐Kiing Lim Elizabeth , Das Shobha S. , Das Amit 
Published: January 2009

AbstractWe use agency theory to predict the influence of related and unrelated product diversification on a firm's level of debt financing. Further, we argue that the link between diversification and capital structure is moderated by the environment in which firms operate. Using SAS PROC MIXED, we fit a mixed‐effects model to our unique six‐year longitudinal dataset (1995–2000) of 245 publicly listed Singapore firms. Our data spans the period of the Asian Financial Crisis (1997–1998). We find that firms pursuing unrelated product diversification take on less debt financing in stable environments, but more debt financing in dynamic environments. Using longitudinal structural equation modeling, we find a reciprocal relationship between a firm's product diversification strategy and its debt financing level. Copyright © 2009 John Wiley & Sons, Ltd.
Validation of GCC optimizers through trace generation
Authors: Kanade Aditya , Sanyal Amitabha , Khedker Uday P. 
Published: January 2009

AbstractThe translation validation approach involves establishing semantics preservation of individual compilations. In this paper, we present a novel framework for translation validation of optimizers. We identify a comprehensive set of primitive program transformations that are commonly used in many optimizations. For each primitive, we define soundness conditions that guarantee that the transformation is semantics preserving. This framework of transformations and soundness conditions is independent of any particular compiler implementation and is formalized in PVS. An optimizer is instrumented to generate the trace of an optimization run in terms of the predefined transformation primitives. The validation succeeds if (1) the trace conforms to the optimization and (2) the soundness conditions of the individual transformations in the trace are satisfied. The first step eliminates the need to trust the instrumentation. The soundness conditions are defined in a temporal logic and therefore the second step involves model checking. Thus the scheme is completely automatable. We have applied this approach to several intraprocedural optimizations of RTL intermediate code in GNU Compiler Collection (GCC) v4.1.0, namely, loop invariant code motion, partial redundancy elimination, lazy code motion, code hoisting, and copy and constant propagation for sample programs written in a subset of the C language. The validation does not require information about program analyses performed by GCC. Therefore even though the GCC code base is quite large and complex, instrumentation could be achieved easily. The framework requires an estimated 21 lines of instrumentation code and 140 lines of PVS specifications for every 1000 lines of the GCC code considered for validation. Copyright © 2009 John Wiley & Sons, Ltd.
XRF analysis of two terracotta polychrome sculptures by Pietro Torrigiano
Authors: Križnar A. , Muñoz M. V. , de la Paz F. , Respaldiza M. A. , Vega M. 
Published: January 2009

AbstractPietro Torrigiano was a very well known Italian sculptor working in the first half of the 16th century. He got his artistic education in the heart of the Renaissance Italy, in the Academia of Florence. Travelling around Europe, he was entrusted by important artistic orders for noble families, courts and the Church. In 1522, he came to Spain where he carried out his latest artworks. Two of them are exposed today in the Fine Arts Museum of Seville: Saint Jerome and Our Lady of Bethlehem. Both sculptures were analyzed by the nondestructive technique of x‐ray fluorescence (XRF) directly in situ in the exposition room. The support and the pigments were analyzed. The raw material in both sculptures is terracotta (characterized by Mn, Al, Si, K, Ca and Fe). The results of the first one, Saint Jerome, show a great part of modern materials applied, such as Ti and Zn white, revealing some retouches or even a repolychromy of the sculpture. The original parts show the use of lead white (Pb), yellow and red ochre (Ca, Fe), cinnabar (Hg) and umbra (Mn, Fe). The spectra of the Our Lady of Bethlehem sculpture show that the bench under the Virgin is not original and it was added later. The original pigments applied were white lead, red ochre, cinnabar, blue azurite, some copper‐based green pigment, umbra and an organic black pigment. Small presence of tin–lead yellow was detected. Decorative parts of the blue Virgin's coat and red pillow were gilded. Also in this sculpture modern pigments were found that confirm later restoration interventions. Copyright © 2009 John Wiley & Sons, Ltd.