bluuebunny/crossref_metadata_2025_split huggingface dataset:
Growth kinetics of AlxGa1–xN layers (0 < x < 1) in plasma‐assisted molecular beam epitaxy
Authors: Mizerov A. M. , Jmerik V. N. , Kop'ev P. S. , Ivanov S. V. 
Published: April 2010

AbstractComparative study of growth kinetics of the AlxGa1‐xN (x = 0‐1) layers of different polarity, grown by plasma assisted molecular beam epitaxy (PA MBE) under different growth conditions (substrate temperature, group III to activated nitrogen and Al to Ga flux ratios) and on different buffer layers, is presented. The 60 °C higher temperature stability of N‐face AlGaN layers is detected. The strong influence of elastic stress on growth kinetics of metal‐polar AlxGa1‐xN (x > 0.2) layers is observed and discussed. It was found that two‐dimensional growth of AlGaN films of the same composition on different buffer layers at TS = 700 °C can be achieved at different group III surface enrichment, the AlGaN(0001)/c‐Al2O3 films exhibiting the atomically smooth surface at group III to activated nitrogen flux ratio FIII/FN *gradually increased from 1.3 to 2 with the x variation from 0.1 to 0.8. In this case the alloy composition is controlled by the variation of Al flux only (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Improved MOCVD growth of GaN on Si‐on‐porous‐silicon substrates
Authors: Ishikawa H. , Shimanaka K. , Azfar bin M. Amir M. , Hara Y. , Nakanishi M. 
Published: April 2010

AbstractThe mechanism of the poor surface morphology of MOCVD‐grown GaN on porous Si (PSi) substrates was explored. Transmission electron microscopy suggests that a vacancy growth of pores starts, which is accompanied by the migration of the top surface of the PSi layer during the initial growth stage of GaN on the AlN inter layer. This causes a lot of pits on top GaN and wavy interface between GaN of the PSi layer, deteriorating the poor surface morphology. The epitaxial Si layer on PSi is effective in suppressing the migration of the top surface of the PSi layer. The GaN film on the epitaxial‐Si/PSi shows a mirror surface with pits‐free and very few cracks. No voids at the interface between the AlN IL and Si/PSi substrate are observed. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Crack formation in GaN on Si(111) substrates grown by MOCVD using HT Al‐preseeding and HT AlN buffer layers
Authors: Kim Jong Ock , Hong Song Ki , Lim Kee Young 
Published: April 2010

AbstractWe have investigated the crack formation in GaN layers grown on Si(111) substrates by MOCVD using an AlN buffer layers and Al‐preseeding process. With an appropriate AlN buffer thickness using optimal TMAl flow rate, we were able to counteract the crack formation usually observed in GaN layers deposited on Si(111) substrate. With a 120 nm thick AlN buffer layer, TMAl source flow rate 18 μmol/min and Al‐preseeding time 5 s, we were able to obtain nearly crack free 2.5 μm GaN surface and a (002) plane HR‐XRD rocking curve FWHM of385 arcsec is achieved. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic properties of group III‐A nitride sheets by molecular simulation
Authors: Anota Ernesto Chigo , Villanueva Martín Salazar , Cocoletzi Heriberto Hernández 
Published: April 2010

AbstractWe have performed first principles total energy calculations to investigate the structural and reactivity parameters of novel N12X12H12 (X=B, Al, Ga, In, Tl) nitrides, in their coronene‐like (C24H12) structure to simulate these sheets. The exchange and correlations potential energies are treated in the Generalized Gradient Approximation (GGA), and the Local Density Approximation (LDA) within the parameterization of Perdew‐Wang and Perdew‐Burke‐Ernzerhof (PWC, PBE) and the double Numeric plus polarization (DNP) atomic base. The chemical potential, hardness and electrophilicity index, as well as bond length are reported. The bond length of the structures is similar to the bulk. The gap between the HOMO and LUMO decreases from BN (5.18 eV) to TlN (1.76 eV). At the same time, the polarity increases except for TlN. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of period of the electron emitter MQW structure on the improvement of characteristics in nitride‐based LEDs
Authors: Su Y. K. , Chen J. J. , Lin C. L. , Kao C. C. , Lin C. T. 
Published: April 2010

AbstractThe effect of period of electron emitter multiple‐quantum well (EE‐MQW) structure on the structural, electrical, and optical characteristics of nitride‐based light‐emitting diodes (LEDs) were investigated. From the lattice constant results of InGaN/GaN multiple‐quantum well (MQW) by the high resolution X‐ray diffraction, the compressive strain of InGaN/GaN MQW could be released gradually when the period of EE‐MQW structure increases. Therefore, the leakage current reduces and the ESD endurance ability enhances with increasing period of EE‐MQW structure. On the other hand, the electron injection efficiency will also be improved by inserting EE‐MQW structure. When the period of EE‐MQW structure increases, the forward voltage and series resistance both decrease. Due to the improved electron injection efficiency and crystalline quality, the luminance intensity increases with increasing period of EE‐MQW structure. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of semipolar (11$ \bar 2 $2) GaN on c ‐plane sapphire sidewall of patterned r ‐plane sapphire substrate without SiO2 mask
Authors: Kurisu Akihiro , Murakami Kazuma , Abe Yuki , Okada Narihito , Tadatomo Kazuyuki 
Published: April 2010

AbstractWe succeeded in growing a semipolar (11$ \bar 2 $2) GaN layer on a patterned r ‐plane sapphire substrate (r ‐PSS) without a SiO2 mask by metal‐organic vapor phase epitaxy. Under various growth conditions, the semipolar (11$ \bar 2 $2) GaN layer was only grown on the c ‐plane‐like sapphire sidewall of the r ‐PSS without a SiO2 mask which shows r ‐PSS is useful to obtain (11$ \bar 2 $2) GaN. The specific characteristics of the (11$ \bar 2 $2) GaN on the r ‐PSS were investigated by X‐ray diffraction measurement, atomic force microscopy (AFM), transmission electron microscopy and photoluminescence. The full width at half maximum of X‐ray rocking curve of coalesced sample were 722 and 319 arcsec along the azimuths parallel and perpendicular to the c ‐direction, respectively. The macrosteps were observed by AFM observation. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Strain effect on optical polarization properties of a ‐plane GaN on r ‐plane sapphire
Authors: Wu Chao , Yu Tongjun , Tao Renchun , Jia Chuanyu , Yang Zhijian , Zhang Guoyi 
Published: April 2010

AbstractIn this study, the optical polarization properties under varying strains in a‐plane GaN were investigated. The valence band (VB) structure for a‐plane GaN is derived from the effective‐mass Hamiltonian based on k·p perturbation theory. The relative oscillator strength (ROS) calculations of the transitions related to the top three VBs near Γ point are applied to analyzing the optical polarized properties. For a‐plane GaN, the main components of the first, the second and the third VBs are |Y 〉‐like (y‐axis // [1$ \bar 1 $00]), |Z 〉‐like (z‐axis // [0001]) and |X 〉‐like (x‐axis // [11$ \bar 2 $0]) states, respectively. Under small compressive strain along c‐axis, the polarization degree increases with compressive strain increasing. According to X‐ray diffraction (XRD) scans and Raman backscattering spectra, both the in‐plane and out‐plane strains were evaluated. Polarized photoluminescence (PL) is employed to obtain the polarization degree. The experimental results of a‐plane GaN samples under different strains showed good accordance with our theoretical calculations (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Light‐emitting diodes fabricated on nanopatterned sapphire substrates by thermal lithography
Authors: Shinagawa Taku , Abe Yuki , Matsumoto Hiroyuki , Li BoCheng , Murakami Kazuma , Okada Narihito , Tadatomo Kazuyuki , Kannaka Masato , Fujii Hideo 
Published: April 2010

AbstractGaN‐based light‐emitting diodes (LEDs) were fabricated on nanopatterned sapphire substrates (nano‐PSSs) by thermal lithography with laser irradiation. The characteristics of the LEDs were measured by X‐ray diffraction analysis and scanning electron microscopy. The crystalline qualities of the LEDs deteriorated with the shortening of the nanopattern periods. The nucleation of GaN was initiated from the nanopatterns, which increased the number of grain boundaries. The output power of the LEDs on the nano‐PSSs with a diameter of 200 nm and 500 nm periods was 70% higher than that on flat sapphire substrate. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Light extraction enhancement from GaN‐based thin‐film LEDs grown on silicon after substrate removal using HNA solution
Authors: Zou Xin Bo , Liang Hu , Lau Kei May 
Published: April 2010

AbstractOne of the promising methods to obtain high optical output power from LEDs grown on Si is to eliminate the absorptive Si substrate. In this paper, we report how GaN‐based thin‐film LEDs grown on silicon (111) substrates by MOCVD were successfully transferred to a copper substrate by room‐temperature electroplating and how the original Si substrate was removed by HNA solution. After fabrication, the III‐nitride LED thin films showed no cracks or degradation. And the light output power of LEDs after Si removal increased by ∼ 30% compared with conventional ones before the Si removal. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An ultraviolet micro‐LED array and its application for microlens fabrication
Authors: Zhu L. , Lai P. T. , Choi H. W. 
Published: April 2010

AbstractWe report on a direct‐write lithographic technique for the fabrication of micro‐lens arrays with an ultraviolet (UV) micro‐light‐emitting diode (LED) array, serving as an exposure source. Owing to the Lambertian emission distribution of LEDs, the exposed UV sensitive coating (UV epoxy) adopts the same profile, resulting in spherical lenses being formed naturally, without further reflow. This technique is distinctive from conventional UV curing method and possesses many advantages, including simplicity of processing, allows control of the dimensions of micro‐lenses through process parameters, and is readily scalable. Micro‐lens arrays of high optical quality have been fabricated by this method. The properties of the lenses are evaluated by optical microscopy and atomic force microscope. The determined focal length is close to the predicted value. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Design of near lattice‐matched AlGaInN‐barriers for highly‐scalable GaN‐based transistor structures
Authors: Lim Taek , Aidam Rolf , Kirste Lutz , Waltereit Patrick , Müller Stefan , Ambacher Oliver 
Published: April 2010

AbstractAlGaInN layers at compositions near lattice‐matched to GaN have been grown by molecular beam epitaxy. X‐ray diffraction and atomic force microscopy show single‐phase quaternary layers with smooth morphology. Heterostructures with thin nearly strain‐free AlGaInN‐barriers exhibit high values for sheet electron density and mobility ranging up to 2.1×1013 cm‐2 and 1240 cm2/Vs, respectively. The epitaxial design of the structures comprises a multi‐layer spacer which enables a wider separation between channel and barrier compared to a single AlN interlayer and serves as a protection during growth. A series of wafers with varied composition in the barrier reveals that the electron mobility increases with Ga‐content in AlGaInN as expected considering the miscibility of quaternary nitrides. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Translation initiation of viral mRNAs
Authors: López‐Lastra Marcelo , Ramdohr Pablo , Letelier Alejandro , Vallejos Maricarmen , Vera‐Otarola Jorge , Valiente‐Echeverría Fernando 
Published: April 2010

AbstractViruses depend on cells for their replication but have evolved mechanisms to achieve this in an efficient and, in some instances, a cell‐type‐specific manner. The expression of viral proteins is frequently subject to translational control. The dominant target of such control is the initiation step of protein synthesis. Indeed, during the early stages of infection, viral mRNAs must compete with their host counterparts for the protein synthetic machinery, especially for the limited pool of eukaryotic translation initiation factors (eIFs) that mediate the recruitment of ribosomes to both viral and cellular mRNAs. To circumvent this competition viruses use diverse strategies so that ribosomes can be recruited selectively to viral mRNAs. In this review we focus on the initiation of protein synthesis and outline some of the strategies used by viruses to ensure efficient translation initiation of their mRNAs. Copyright © 2010 John Wiley & Sons, Ltd.
Ni and Ni alloy coatings electrodeposited from choline chloride‐based ionic liquids—electrochemical synthesis and characterization
Authors: Florea A. , Anicai L. , Costovici S. , Golgovici F. , Visan T. 
Published: April 2010

AbstractThis study deals with some preliminary experimental results regarding the electrodeposition and characterization of Ni and Ni alloy coatings, respectively, NiMo and NiSn, from some choline chloride‐based ionic liquids. The obtained Ni deposits are adherent, uniform onto Cu substrate. According to X‐ray diffraction investigations, average sizes of the crystallites have been in the range of 9.2–14.4 nm, higher for increased applied current densities, maybe as a result of the increase in temperature during electrodeposition. In addition, an amorphous phase was evidenced. NiMo alloy coatings have been obtained for the first time from ionic liquids containing 0.42 M NiCl2·6H20 and 0.016 M ammonium heptamolybdate in choline chloride‐urea‐citric acid or chloline chloride–ethylene glycol–citric acid mixtures. NiSn alloys were formed in choline chloride–urea and choline chloride–ethylene glycol solvents, with various additions of Ni and Sn salts. The obtained alloy deposits are adherent, uniform onto Cu substrate. To obtain information on the deposits' morphology and composition, atomic force microscopy, SEM and energy‐dispersive X‐ray techniques were used and the results are discussed taking into account the ionic liquid type, composition and conductivity in close correlation with electrochemical conditions. Copyright © 2010 John Wiley & Sons, Ltd.
Synthesis, physicochemical characterization, and preliminary molecular modeling studies of SnO2 nanoparticles
Authors: Ionita Mariana , Branzoi Ioan Viorel , Popa Laurentiu 
Published: April 2010

AbstractThe aim of this work is to provide reliable and accurate experimental and modeling studies for the design and investigation of tin dioxide nanoparticles. SnO2 particles were prepared by following a sol–gel preparative route using tin (IV) alkoxide as the starting compound. The xerogels were thermally treated at 300, 500 and 700 °C, in different gaseous environments (oxygen, air, He). The powders were characterized for phase composition‐crystallinity, specific surface area and surface composition. Computational models of SnO2 were implemented, total energy of the systems was minimized by using COMPASS force field and further lattice parameters were assessed. The conditions adopted in the preparative route played an important role on the physicochemical properties of SnO2 nanoparticles. The size of the crystallites was found to increase with the heating temperature and to depend on the gassing atmosphere adopted during the thermal treatment. Computational and experimental lattice parameters are not appreciably affected by the variables of the synthesis and are in good agreement with structural data for the cassiterite lattice. Overall, the agreement between experimental data and simulation results is satisfactory. Copyright © 2010 John Wiley & Sons, Ltd.
Electrochemical fabrication and capacitance of composite films of carbon nanotubes and polyaniline
Authors: Branzoi Viorel , Branzoi Florina , Pilan Luisa 
Published: April 2010

AbstractNanoporous composite films of single‐walled carbon nanotubes (CNTs) and polyaniline (PANI) were grown electrochemically on a platinum electrode with the aim to investigate the influence of the forming process, and thus the influence of the microstructure, on the capacitive performance of the composites. The constituents of the composite were deposited either simultaneously from acidic aqueous solutions containing both the CNTs and the monomer, or by PANI electrodeposition on an electrode already modified by adsorbed CNT coating. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were used to investigate the electrochemical properties of the composite films. The electrochemical response is significantly increased for the composite films in comparison with the pure polymer film. Scanning electron microscopy revealed that the composite films consisted of nanoporous networks of CNTs coated with PANI. Copyright © 2010 John Wiley & Sons, Ltd.
Analysis of interval‐censored disease progression data via multi‐state models under a nonignorable inspection process
Authors: Chen Baojiang , Yi Grace Y. , Cook Richard J. 
Published: April 2010

AbstractIrreversible multi‐state models provide a convenient framework for characterizing disease processes that arise when the states represent the degree of organ or tissue damage incurred by a progressive disease. In many settings, however, individuals are only observed at periodic clinic visits and so the precise times of the transitions are not observed. If the life history and observation processes are not independent, the observation process contains information about the life history process, and more importantly, likelihoods based on the disease process alone are invalid. With interval‐censored failure time data, joint models are nonidentifiable and data analysts must rely on sensitivity analyses to assess the effect of the dependent observation times. This paper is concerned, however, with the analysis of data from progressive multi‐state disease processes in which individuals are scheduled to be seen at periodic pre‐scheduled assessment times. We cast the problem in the framework used for incomplete longitudinal data problems. Maximum likelihood estimation via an EM algorithm is advocated for parameter estimation. Simulation studies demonstrate that the proposed method works well under a variety of situations. Data from a cohort of patients with psoriatic arthritis are analyzed for illustration. Copyright © 2010 John Wiley & Sons, Ltd.
Multi‐state Markov models for disease progression in the presence of informative examination times: An application to hepatitis C
Authors: Sweeting M. J. , Farewell V. T. , De Angelis D. 
Published: April 2010

AbstractIn many chronic diseases it is important to understand the rate at which patients progress from infection through a series of defined disease states to a clinical outcome, e.g. cirrhosis in hepatitis C virus (HCV)‐infected individuals or AIDS in HIV‐infected individuals. Typically data are obtained from longitudinal studies, which often are observational in nature, and where disease state is observed only at selected examinations throughout follow‐up. Transition times between disease states are therefore interval censored. Multi‐state Markov models are commonly used to analyze such data, but rely on the assumption that the examination times are non‐informative, and hence the examination process is ignorable in a likelihood‐based analysis. In this paper we develop a Markov model that relaxes this assumption through the premise that the examination process is ignorable only after conditioning on a more regularly observed auxiliary variable. This situation arises in a study of HCV disease progression, where liver biopsies (the examinations) are sparse, irregular, and potentially informative with respect to the transition times. We use additional information on liver function tests (LFTs), commonly collected throughout follow‐up, to inform current disease state and to assume an ignorable examination process. The model developed has a similar structure to a hidden Markov model and accommodates both the series of LFT measurements and the partially latent series of disease states. We show through simulation how this model compares with the commonly used ignorable Markov model, and a Markov model that assumes the examination process is non‐ignorable. Copyright © 2010 John Wiley & Sons, Ltd.
Causal loop diagrams between structure and behaviour: A critical analysis of the relationship between polarity, behaviour and events
Authors: Schaffernicht Martin 
Published: April 2010

AbstractCausal loop diagrams (CLDs) are a qualitative diagramming language for representing feedback‐driven systems. One of their conceptual cornerstones—polarity—has been critiqued for some shortcomings. However, their use has not diminished, and polarity, as well as the relationship between behaviour and events continues to be used in a pragmatic way. A definition of how events relate to behaviour is proposed for a world of continuous behaviour. Then, several previously unconsidered limitations of CLDs are discussed, which prove to be closer to the event‐related thinking and therefore provide little help in avoiding faulty thinking about the behavioural consequences of causal structure. Also, the reasons underlying previously discussed limitations of CLDs become clear. Polarity is shown to be an interface between behaviour and structure. Inexperienced users need external help to use polarity in going from behaviour to structure and back. Such help could come from incorporating behaviour‐over‐time (BOT) graphs into the diagrams. Several areas of further research are identified. Copyright © 2010 John Wiley & Sons, Ltd.
The deletion of YLR042c improves ethanolic xylose fermentation by recombinant Saccharomyces cerevisiae
Authors: Parachin Nádia S. , Bengtsson Oskar , Hahn‐Hägerdal Bärbel , Gorwa‐Grauslund Marie‐F. 
Published: April 2010

AbstractIn a recent study combining transcriptome analyses of a number of recombinant laboratory and industrial S. cerevisiae strains with improved xylose utilization and their respective control strains, the ORF YLR042c was identified as a downregulated gene and it was shown that the gene deletion improved aerobic growth on xylose in the tested strain background. In the present study, the influence of deleting YLR042c on xylose fermentation was investigated in two different xylose‐fermenting strains: TMB3001, which expresses genes from the initial xylose catabolizing pathway, including heterologous xylose reductase (XR) and xylitol dehydrogenase (XDH) and endogenous xylulokinase (XK); and TMB3057, which, in addition to the initial xylose catabolizing pathway, overexpresses the endogenous genes encoding the non‐oxidative pentose phosphate pathway enzymes. The deletion of YLR042c led to improved aerobic growth on xylose in both strain backgrounds. However, the effect was more significant in the strain with the poorer growth rate on xylose (TMB3001). Under anaerobic conditions, the deletion of YLR042c increased the specific xylose consumption rate and the ethanol and xylitol yields. In strain TMB3057, xylose consumption was also improved at low concentrations and during co‐fermentation of xylose and glucose. The effect of the gene deletion and overexpression was also tested for different carbon sources. Altogether, these results suggest that YLR042c influences xylose and the assimilation of carbon sources other than glucose, and that the effect could be at the level of sugar transport or sugar signalling. Copyright © 2010 John Wiley & Sons, Ltd.