bluuebunny/crossref_metadata_2025_split huggingface dataset:
Controlled formation of voids at the AlN/sapphire interface by sapphire decomposition for self‐separation of the AlN layer
Authors: Tajima J. , Kubota Y. , Ishizuki M. , Nagashima T. , Togashi R. , Murakami H. , Kumagai Y. , Takada K. , Koukitu A. 
Published: May 2009

AbstractSelf‐separation of hydride vapor phase epitaxy (HVPE)‐grown AlN layer from sapphire substrate was achieved by the formation of voids at the AlN/sapphire interface. Voids could be formed through the decomposition of sapphire beneath a thin (100 nm) protective AlN layer grown at 1065 °C by heating at 1450 °C in a carrier gas (H2 + N2) containing NH3. Additionally, the void size could be controlled by varying the heating time. As the results of controlled formation of voids, after growth of a thick (85 μm) AlN layer on the thin protective AlN layer heated at 1450 °C for 30 min, self‐separation of the AlN layer from a sapphire substrate occurred by the compressive stress from difference in thermal expansion coefficients between AlN and sapphire during post‐growth cooling. The self‐separated thick AlN layer had low concentration of impurities, and showed clear photoluminescence peak at 208.4 nm. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
I‐V and C‐V characteristics of rare‐earth‐metal/p‐GaN Schottky contacts
Authors: Fukushima Yoshihiro , Ogisu Keita , Kuzuhara Masaaki , Shiojima Kenji 
Published: May 2009

AbstractThe electrical properties of rare‐earth‐metal Schottky contacts to p‐GaN were characterized with current‐voltage (I‐V) and capacitance‐voltage (C‐V) measurements for the first time. Three kinds of rare‐earth‐metal films of Dy, Er, and Gd, which have low‐metal‐work‐function nature, were deposited on low‐Mg‐doped p‐GaN. Linear regions of more than one and a half orders were seen in a forward semi‐log I‐V plot, and reverse break down voltages were as high as around 60 V for all samples. In the C‐V characteristics, good linearity was obtained in a 1/C2 plot for all samples. The carrier concentration was estimated to be about 5.5×1016 cm–3, which is a reasonable value of activation efficiency of 4.2%. The Schottky barrier heights of Dy, Er, and Gd contacts were 1.91, 2.38, and 2.16 eV from I‐V, and 1.79, 1.78, and 1.70 eV from C‐V, respectively. These values are as high as those of the transition metal contacts. These results tell us that Fermi level pinning is significantly strong for p‐GaN surfaces with a conventional acid treatment. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High‐power GaN‐HEMT with high three‐terminal breakdown voltage for W‐band applications
Authors: Makiyama Kozo , Ohki Toshihiro , Kanamura Masahito , Joshin Kazukiyo , Imanishi Kenji , Hara Naoki , Kikkawa Toshihide 
Published: May 2009

AbstractIn this paper, we reported on a technology to improve the three‐terminal breakdown voltage of a GaN high electron mobility transistor (GaN‐HEMT) for a millimetre‐wave amplifier. To fabricate high‐power and high‐efficiency GaN‐HEMT millimetre‐wave amplifier, it is necessary to improve the three‐terminal breakdown voltage and the pinched‐off current. In this work, the thickness of the GaN channel layer and the quality of the channel layer has been improved by adding small quantities of Al to the GaN buffer. We demonstrated a high maximum frequency of oscillation (fmax) of over 200 GHz with a pinched‐off current of 10–6 A/mm at Vds of 50 V for a device with a gate length of 100 nm. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The effect of absorption layer of different quantum well arrangement on optoelectronic characteristics of nitride‐based photovoltaic cells grown by MOCVD
Authors: Fu Y. K. , Tun C. J. , Kuo C. W. , Kuo C. H. , Pan C. J. , Chi G. C. , Chen M. C. , Hong H. F. , Lan S. M. 
Published: May 2009

AbstractIn this study, III‐nitride solar cells with multi‐quantum well (MQW) absorption layer were grown on sapphire substrates by metal organic chemical vapor deposition (MOCVD). The effect of different quantum well (QW) arrangement on optoelectronic characteristics of III‐nitrides photovoltaic cells was investigated. It was found that the upper quantum well (QW) layer will dominate electroluminescence (EL) emission mechanism and the electrical characteristics of solar cell.The advantage of modulating the short‐circuit current density (JSC) and open‐circuit voltage (VOC) can be obtained by different arrangement of blue and green QW in MQW absorption layer. The optimum electrical characteristics of solar cell with a JSC of 0.30 mA/cm2, a VOC up to 1.51 V, fill factor (FF) as high as 0.601, and a series resistance (RS) of 9 Ω can be obtained by using MQW absorption layer. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Improvement of crystal quality of GaN grown on AlN template by MOCVD using HT‐AlN interlayer
Authors: Yuebin Tao , Zhizhong Chen , Zhijian Yang , Liwen Sang , Zhitao Chen , Ding Li , Hao Fang , Yaobo Pan , Jianfeng Yan , Guangmin Zhu , Cheng Chen , Shitao Li , Maosheng Hao , Guoyi Zhang 
Published: May 2009

AbstractTwo GaN samples, with and without high temperature (HT)‐AlN interlayer (labelled as sample A and B, respectively) grown by MOCVD on AlN template, were investigated by double‐crystal X‐ray diffraction (DC‐XRD), photoluminescence (PL), and atomic force microscope (AFM) measurements. It was found that the crystal quality of GaN could be greatly improved by the HT‐AlN interlayer. The full width at half maximum (FWHM) of (102) reflection in XRD rocking curve was narrower for sample A than that for sample B. However, the FWHMs of (002) reflections were almost the same for the two samples. In addition, the tilt degree which reflected screw dislocation density was almost the same, while the twist degree which reflected edge dislocation density changed from 0.214° to 0.152° when the HT‐AlN interlayer was used. Both the intensities of (102) reflection in XRD and band edge emission in PL for sample A were stronger too. In the AFM images, the atomic growth steps of sample A were clearer than those of sample B. According to the results of the in situ optical reflectivity spectra and the atomic force microscope (AFM) images, the above results were attributed to the three‐dimensional (3D) growth mode of the HT‐AlN interlayer. The HT‐AlN interlayer may work as a kind of “micro‐area” seed for epitaxial lateral overgrowth (ELOG) resulting in bending some dislocations. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determination of the thermo‐optic coefficients of GaN and AlN up to 515 °C
Authors: Watanabe Naoki , Kimoto Tsunenobu , Suda Jun 
Published: May 2009

AbstractThe refractive index dispersions of hexagonal GaN and AlN have been investigated to determine the thermo‐optic coefficients. Measurements were conducted at temperatures ranging from room temperature up to 515 °C in the wavelength range from the near band‐edge to 1000 nm. Optical interference measurements with vertical incident configuration were employed to precisely evaluate the ordinary refractive indices. Optical simulation of AlGaN/GaN distributed Bragg reflectors was also carried out by using the obtained thermo‐optic coefficients. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the origin of IQE‐‘droop’ in InGaN LEDs
Authors: Laubsch Ansgar , Sabathil Matthias , Bergbauer Werner , Strassburg Martin , Lugauer Hans , Peter Matthias , Lutgen Stephan , Linder Norbert , Streubel Klaus , Hader Jörg , Moloney Jerome V. , Pasenow Bernhard , Koch Stephan W. 
Published: May 2009

AbstractWe identify a quantum well internal high density Augerlike loss process as the origin of the so called ‘droop’ of internal quantum efficiency (IQE) in InGaN based light emitters. The IQE of such a device peaks at small current densities and then monotonously decreases towards higher currents. The origin of this ‘droop’ has been widely discussed recently and many possible mechanisms have been proposed for explaining the effect. We compare temperature and carrier density dependent electroluminescence and photoluminescence measurements of a green emitting single quantum‐well (SQW) LED over a wide parameter range. The carrier‐density as well as temperature dependence of efficiency is identical in both measurements, indicating that the decrease is due to a high density quantum‐well internal loss process. The data can be accurately modeled assuming an Auger‐like loss process with C = 3.5 × 10–31 cm6s–1. We suggest phonon‐ or defect‐assisted Auger recombination as the origin of this loss‐channel. The high current performance can be improved if a thick InGaN SQW or a multi quantum‐well (MQW) is used. This is in very good agreement with theoretical simulations (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mechanism of thermal degradation in GaInN/GaN quantum wells
Authors: Bremers H. , Jönen H. , Hoffmann L. , Rossow U. , Hangleiter A. 
Published: May 2009

AbstractIn this contribution we focus on degradation processes of GaInN multiple quantum wells (MQWs) used in laser structures grown by metallorganic vapor pressure epitaxy (MOVPE). The influence of ramp‐up time as well as the maximum temperature during growth of the barrier on the quantum well (QW) is investigated. Comparison of X‐ray and photoluminescence (PL) measurements implies that a sufficient thickness of a cover layer grown at low temperature is required to prevent degradation of the QW.In a next step samples were grown using an optimal thermal budget during growth of the active region to investigate the influence of capping layers. To improve crystalline quality of these layers high temperatures are required. Our measurements show that these high temperatures lead to a decrease in average indium concentration of the QWs. This decrease is temperature as well as time dependent (∝ √t) and can only explained by diffusion processes. The activation energies are in the range 0.7‐0.9 eV (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Non‐Gaussian conductance noise in disordered electronic systems [Phys. Status Solidi C 5, No. 3, 809–813 (2008)]
Authors: Orlyanchik V. , Kozub V. I. , Ovadyahu Z. 
Published: May 2009

AbstractThe abstract of the paper contained an error. The corrected abstract is given below. Note that the only change is in the last sentence which has to be read: “It is concluded that the non‐Gaussian features can be observed whether or not the system is glassy.” (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A new generalization of Weibull distribution with application to a breast cancer data set
Authors: Wahed Abdus S. , Luong The Minh , Jeong Jong‐Hyeon 
Published: May 2009

AbstractIn this article, we propose a new generalization of the Weibull distribution, which incorporates the exponentiated Weibull distribution introduced by Mudholkar and Srivastava (IEEE Trans. Reliab. 1993; 42:299–302) as a special case. We refer to the new family of distributions as the beta‐Weibull distribution. We investigate the potential usefulness of the beta‐Weibull distribution for modeling censored survival data from biomedical studies. Several other generalizations of the standard two‐parameter Weibull distribution are compared with regards to maximum likelihood inference of the cumulative incidence function, under the setting of competing risks. These Weibull‐based parametric models are fit to a breast cancer data set from the National Surgical Adjuvant Breast and Bowel Project. In terms of statistical significance of the treatment effect and model adequacy, all generalized models lead to similar conclusions, suggesting that the beta‐Weibull family is a reasonable candidate for modeling survival data. Copyright © 2009 John Wiley & Sons, Ltd.
A selection model for longitudinal binary responses subject to non‐ignorable attrition
Authors: Alfò Marco , Maruotti Antonello 
Published: May 2009

AbstractLongitudinal studies collect information on a sample of individuals which is followed over time to analyze the effects of individual and time‐dependent characteristics on the observed response. These studies often suffer fromattrition: individuals drop out of the study before its completion time and thus present incomplete data records. When the missing mechanism, once conditioned on other (observed) variables, does not depend on current (eventually unobserved) values of the response variable, the dropout mechanism is known to be ignorable. We propose a selection model extending semiparametric variance component models for longitudinal binary responses to allow for dependence between the missing data mechanism and the primary response process. The model is applied to a data set from a methadone maintenance treatment programme held in Sidney, 1986. Copyright © 2009 John Wiley & Sons, Ltd.
A customizable pattern‐based software process simulation model: design, calibration and application
Authors: Garousi Vahid , Khosrovian Keyvan , Pfahl Dietmar 
Published: May 2009

AbstractSoftware process analysis and improvement relies heavily on empirical research. Empirical research requires measurement, experimentation, and modeling. However, whatever evidence is gained via empirical research is strongly context dependent. Thus, it is hard to combine results and capitalize upon them for the purpose of improvement in evolving development environments. The process simulation model GENSIM 2.0 addresses these challenges. GENSIM 2.0 is a generic process simulation tool representing V‐model type software development processes. Compared to existing process simulation models in the literature, the novelty of GENSIM 2.0 is twofold. Firstly, its model structure is customizable to organization‐specific processes. This is achieved by using a limited set of generic structures (macro‐patterns). Secondly, its model parameters can be easily calibrated to available empirical data and expert knowledge. This is achieved by making the internal model structures explicit and by providing guidance on how to calibrate model parameters. This article outlines the structure of GENSIM 2.0, gives examples on how to calibrate the model to available empirical data, and demonstrates its usefulness through two application scenarios The first scenario illustrates how GENSIM 2.0 helps in finding effective combinations of verification and validation techniques under given time and effort constraints. The second scenario shows how the simulator supports in finding the best combination of alternative verification techniques. Copyright © 2009 John Wiley & Sons, Ltd.
Antimalarial natural products of marine and freshwater origin
Authors: Gademann Karl , Kobylinska Joanna 
Published: May 2009

AbstractThis review highlights recently discovered antimalarial natural products from marine and freshwater sources described in the literature from 2006 to 2008. The structures as well as bioactivities of compounds against the malaria parasites such asPlasmodium falciparumare discussed, including, for example, agelasine, xestoquinone, alisiaquinone, crambescidin, venturamide, dragomabin, gragonamide, viridamide, salinosporamide, chaetoxanthone, nodulisporacid, tumonoic acid, girolline, oroidin, nostocarboline, aerucyclamide, and microcylamide 7806 and its revised structure. Synthetic derivatives of natural products are presented including plakortin, isoaaptamine, curcuphenol, pseudopyronine, manzamine, and nostocarboline. Consequences of these discoveries for the development of novel natural product agents against malaria are discussed. © 2009 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 9: 187–198; 2009: Published online in Wiley InterScience (www.interscience.wiley.com)DOI 10.1002/tcr.200900001
Operative Debridement of Pressure Ulcers
Authors: Schiffman Jessica , Golinko Michael S. , Yan Alan , Flattau Anna , Tomic‐Canic Marjana , Brem Harold 
Published: May 2009

AbstractBackgroundInfection in severe pressure ulcers can lead to sepsis with a 6‐month mortality as high as 68%.MethodsOperative records of 142 consecutive operative debridements on 60 patients in a dedicated wound healing inpatient unit were reviewed, from the Wound Electronic Medical Record, for identification of key steps in debridement technique, mortality, unexpected returns, and time to discharge following debridement.ResultsThe mean age of the patients was 73.1 years, and 45% were men. Most wounds (53%) were located on the hip (ischial or trochanteric); others were on the sacrum (32%) and the heels (14%). The mean initial wound area prior to debridement was 14.0 cm2, and 83% of debridements were performed on stage IV pressure ulcers. The postoperative hospital stay averaged 4.1 days. Key steps in the technique included (1) exposure of areas of undermining by excising overlying tissue; (2) removal of callus from wound edges; (3) removal of all grossly infected tissue; and (4) obtaining a biopsy of the deep tissue after debridement of all nonviable or infected tissue for culture and pathology to determine the presence of infection, fibrosis, and granulation tissue. There was one death 9 days post‐debridement of a sacral ulcer and one unplanned return to the operating room for bleeding 8 days post‐debridement.ConclusionsOperative debridement of pressure ulcers is safe, despite the medical co‐morbidities in patients with severe pressure ulcers. Proper debridement technique may prevent sepsis and death in patients with multiple co‐morbid conditions.
Is the Retrojugular Approach Safer Than the Conventional Approach for Carotid Endarterectomy?
Authors: Kluk J. , Grainger S. , Nyamekye I. K. 
Published: May 2009

AbstractBackgroundThe retrojugular approach is promoted as an alternative to traditional antejugular carotid endarterectomy. Absence of named posterior venous branches and ease of distal internal carotid dissection reduce time for carotid exposure together with improved distal exposure. However, a higher incidence of local nerve injury and persistent hoarse voice has been reported. We compare the incidence of these and other complications for the antejugular and retrojugular approaches.DesignThis is a nonrandomised retrospective review of prospectively collected data on consecutive patients undergoing carotid endarterectomy.ResultsOur 178 patients formed two groups who were homogeneous in terms of sex and age. Mean operative times, patch usage, and general/local anaesthesia did not differ significantly for the two groups. Postoperative complications including transient ischemic attack (TIA), major stroke, or death; hypertension; miosis; and hypoglossal injury were similar for the two groups. However, there was a significantly increased incidence of persistent hoarse voice (p < 0.05) in the retrojugular group.ConclusionsReports of increased incidence of persistent hoarse voice associated with the retrojugular approach to carotid endarterectomy are supported by our findings, which point to a learning curve effect. A randomized controlled trial would be necessary before any strong recommendation could be made for or against the retrojugular approach.
Surgical Management of Giant Liver Tumor Involving the Hepatic Hilum of Children
Authors: Dong Qian , Jiang Buxian , Lu Yun , Zhang Hong , Jiang Zhong , Lu Hongting , Yang Chuanmin , Zhao Jing , Hao Xiwei 
Published: May 2009

AbstractBackgroundSurgical management of giant liver tumors involving the hepatic hilum tends to be very difficult. The present study assessed the feasibility and safety of resection of such liver tumors.MethodsWe evaluated 27 patients with liver tumors involving the hepatic hilum. The patients ranged in age from 3 months to 14 years (mean, 4.2 years). Of the 27 cases, 23 were resected completely during the past 10 years. The other four cases did not undergo operation because of their parents’ decisions to discontinue treatment; these cases had multiple space‐occupying lesions in addition to tumors involving the hepatic hilum. Before resection, the tumor was fully exposed and an occluding tape was placed around the vena cava when necessary.ResultsThe hepatectomies were performed under intermittent portal triad clamping; 23 cases were successfully resected without postoperative mortality or morbidity. The mean operation duration was 205 min and mean blood loss was 120 ml. Pathological diagnoses included hepatoblastoma (n = 9), endotheliosarcoma (n = 1), mesenchymal hamartoma (n = 4), teratoma (n = 1), adenoma (n = 3), and hepatocellular carcinoma (n = 4). The nine cases with benign liver tumors were healthy at follow‐up at 11 months to 9 years after operation. Of the 14 cases with malignant tumors, six died from recurrence, metastasis, or other complications. The other eight cases were still alive without clinical tumors.ConclusionsResecting giant liver tumors involving the main hepatic veins and/or the retrohepatic vena cava, although challenging, is feasible and safe.
Use of India Ink During Preoperative Computed Tomography Localization of Small Peripheral Undiagnosed Pulmonary Nodules for Thoracoscopic Resection
Authors: Magistrelli Prospero , D’Ambra Luigi , Berti Stefano , Feleppa Cosimo , Stefanini Teseo , Falco Emilio 
Published: May 2009

AbstractBackgroundComputed tomography (CT) scans of the chest permit us to identify a large number of small peripheral, undefined pulmonary lesions that require a diagnosis. Broncoscopy results are generally negative in these cases, and needle aspiration results are often inconclusive owing to poor cytology and false‐negative cases. Thoracoscopy is an ideal tool but allows us only to localize lesions that retract the visceral pleura. Our aim in this study was to establish a marking procedure for excising nodules of unknown etiology by injecting India ink on the surface of the lung.MethodsSince January 2008, eight patients (six men, two women) who had been diagnosed as having a peripheral small pulmonary nodule of unknown etiology were selected for preoperative tattooing under CT guidance to facilitate thoracoscopic wedge resection.ResultsIn six cases, thoracoscopy allowed diagnosis and definitive treatment of two benign peripheral nodules and four single metastases from colon carcinoma. In two patients who had been diagnosed to have a primitive non‐small‐cell lung cancer on frozen section following thoracoscopy, the surgical treatment was concluded with limited lateral thoracotomy and lobectomy with ilomediastinal node dissection.ConclusionsOur experience suggests that this CT technique, which includes using India ink to label and localize peripheral small pulmonary nodules, is a safe, valid option for marking the lung, thereby facilitating subsequent thoracoscopic resection.