bluuebunny/crossref_metadata_2025 huggingface dataset:
HPV16‐E6 associated hTERT promoter acetylation is E6AP dependent, increased in later passage cells and enhanced by loss of p300
Authors: James Michael A. , Lee John H. , Klingelhutz Aloysius J.
Published: May 2006

The E6 oncoprotein from high‐risk HPV types activates human telomerase reverse transcriptase (hTERT) transcription in human keratinocytes. Studies on how E6 regulates hTERT have implicated E‐box or X‐box elements in the hTERT promoter (Veldman et al., Proc Natl Acad Sci USA 2003;100:8211–14; Oh et al., J Virol 2001;75:5559–66; Gewin et al., Genes Dev 2004;18:2269–82), but the mechanism of activation by E6 is still controversial and not well defined. Here, we demonstrate that induction of both hTERT expression and telomerase activity by HPV‐16 E6 in early passage keratinocytes is associated with acetylation of histone H3 at the hTERT promoter, is dependent on the E6 associated protein (E6AP) and is not exclusively reliant on E‐box or X‐box elements. Further increases in histone acetylation of the hTERT promoter and hTERT transcriptional activity in E6 expressing cells that had been passaged extensively in culture were found to occur only with the endogenous promoter and not with an exogenously introduced hTERT promoter construct. Telomerase activity at both early and late passages, however, was dependent on E6AP expression, implying a continued reliance on E6 function for telomerase activity. Our results demonstrate that E6 induces hTERT promoter acetylation, but that further increases in telomerase activity and histone acetylation in later passage E6 expressing cells are independent of E6 activation of the core hTERT promoter. We also provide evidence that the transcription factor p300 is a potential repressor of telomerase activation and histone acetylation in the context of E6 expression. These studies give insight into how immortalization by HPV results in upregulation of hTERT and furthers our understanding of how telomerase is activated during the process of malignant transformation. © 2006 Wiley‐Liss, Inc.
A BAC library for the goldfish Carassius auratus auratus (Cyprinidae, Cypriniformes)
Authors: Luo Jing , Lang Michael , Salzburger Walter , Siegel Nicol , Stölting Kai N. , Meyer Axel
Published: May 2006

A goldfish (Carassius auratus auratus) bacterial artificial chromosome genomic library (BAC library) was constructed from one aquarium‐bred male specimen (tetraploid, 4n=100, genome size=3.52 pg/cell). The library consists of 128,352 positive clones with an average insert size of 150.4 kb, covering the genome 11‐fold. All clones were spotted onto nylon filters and thus are available for screening of genomic regions of interest, such as candidate genes, gene families, or large‐sized syntenic DNA regions of cyprinid species. Preliminary screens with two genes were conducted with hybridizing probes to the genes RAG1 and lgi1. RAG1 is a single‐copy gene in zebrafish and is duplicated in C. a. auratus. We found a very close correlation between the number of positive BAC clones and the expected library coverage. Two copies of lgi1 were found in zebrafish. We have detected four different copies in C. a. auratus, not in the expected abundance, which indicates some variation in the coverage of the BAC library. The preliminary screens indicate that many duplicated genes that resulted from the ancient fish‐specific genome duplication persist in the tetraploid goldfish genome. Hence, the BAC library will provide a useful resource for the future work on comparative genomics, polyploidy, diploidization, and evolutionary genomics in fishes. J. Exp. Zool. (Mol. Dev. Eiol.) 306B, 2006. © 2006 Wiley‐Liss, Inc.
A novel interpretation of the hyperbolization method used to solve the parabolic neutron diffusion equations by means of the wave digital concept
Authors: Luhmann Katrin , Ochs Karlheinz
Published: May 2006

In this paper, the neutron diffusion equations in two energy groups will be dealt with. The underlying parabolic differential equations as well as a hyperbolized version of them will be numerically solved with the wave digital concept. While the hyperbolization process avoids delay‐free directed loops in the wave flow diagram, a direct implementation of the parabolic differential equations does not. However, an iteration method can be used to overcome these problems. This results under certain conditions in the same wave digital model. This way, it can be shown that the commonly used hyperbolization can be interpreted as the application of an iteration method. Copyright © 2006 John Wiley & Sons, Ltd.
A bidirectional “αvβ3 integrin‐ERK1/ERK2 MAPK” connection regulates the proliferation of breast cancer cells
Authors: Vellon Luciano , Menendez Javier A. , Lupu Ruth
Published: May 2006

In addition to their role in cell migration and adhesion, integrins elicit a series of transduction events that regulate cell‐cycle progression and apoptosis in a process known as “outside‐in” signaling. A second mode of integrin regulation known as “inside‐out” signaling, in which the activation of major cell transduction cascades can influence the activation status of some integrins, has also been described. Here, we have assessed the role of the extracellular signal‐regulated kinase (ERK1)/ERK2, mitogen‐activated protein kinase (MAPK), and phospoinositide 3‐kinase (PI‐3′K) signaling pathways in the expression and function of αvβ3 integrin in breast cancer models. Pharmacological inhibition of MEK1 and MEK2 with U0126 drastically increased the levels of αvβ3 in Heregulin (HRG)‐overexpressing MDA‐MB‐231 cells (231/WT, 231/VEC) and derivatives transfected with the antisense orientation of the HRG‐β2 full length cDNA (231/ASPOOL, 231/AS31). Interestingly, this was related to a significant decrease of viability and of the S‐ and G2/M subcompartment of the cell cycle in MDA MB 231 cells in response to U0126. Furthermore, specific inhibition of the PI‐3′K pathway with LY294002 also induced an increase of αvβ3 levels but to a lesser extent. Moreover, pretreatment of MDA‐MB‐231 cells with U0126 antagonized the effects of small peptidomimetic αvβ3 antagonists. Remarkably, inhibition of the PI‐3′K/AKT pathway did not exert the same effects, thus suggesting that the “outside‐in” as well as the “inside‐out” αvβ3‐mediated signaling goes primarily through the ERK1/ERK2 MAPK pathway in MDA MB 231 breast cancer cells. Collectively, these results strongly suggest the existence of a bidirectional molecular connection αvβ3‐ERK1/ERK2 MAPK that would regulate breast cancer cells survival and proliferation. © 2006 Wiley‐Liss, Inc.
Role of polyamines in arginine‐dependent colon carcinogenesis in ApcMin/+ mice
Authors: Yerushalmi Hagit F. , Besselsen David G. , Ignatenko Natalia A. , Blohm‐Mangone Karen A. , Padilla‐Torres Jose L. , Stringer David E. , Guillen Jose M. , Holubec Hana , Payne Claire M. , Gerner Eugene W.
Published: May 2006

We evaluated the role of polyamines in arginine‐dependent intestinal tumorigenesis in ApcMin/+ mice. Arginine is a substrate for ornithine synthesis and thus can influence polyamine production. Supplementing the diet with arginine increased intestinal and colonic polyamine levels and colonic carcinogenesis. Inhibiting polyamine synthesis with D,L‐α‐diflouromethylornithine (DFMO) decreased small intestinal and colonic polyamine pools. In mice provided basal diet, but not when supplemented with arginine, DFMO decreased small intestinal tumor number and burden, and increased intestinal apoptosis. In mice provided supplemental arginine in the diet, DFMO induced late apoptosis and decreased tumorigenesis in the colon. DFMO slightly reduced tumor incidence, number, and size while significantly decreasing tumor burden and grade. These changes in colon tumorigenesis did not occur in mice not provided supplemental arginine. Our study indicates that polyamines play unique roles in intestinal and colonic carcinogenesis in ApcMin/+ mice. Inhibition of polyamine synthesis suppresses the arginine‐dependent risk of colon tumorigenesis, resulting in apoptosis induction and decreased tumorigenesis, in this murine model. © 2006 Wiley‐Liss, Inc.
Cell‐cycle regulation and mammalian gametogenesis: A lesson from the unexpected
Authors: Kierszenbaum Abraham L.
Published: May 2006

The progression of mammalian gametogenesis requires a precise balance between cell‐cycle activities and elimination of defective gametogenic cells to ensure the perpetuation of species. Both spermatogonia and oogonia are stem cell populations committed to meiosis with the aim of generating haploid gametes for fertilization. At puberty, mitotically dividing spermatogonial cell cohorts maintain the ability of cell renewal and occupy niches in the seminiferous tubule. In contrast, mitotically dividing oogonial cell cohorts produced in the fetal ovary, are exclusively committed to meiosis and produce primordial follicles housing a primary oocyte surrounded by somatic follicular cells. A consistent physiological event during mammalian gametogenesis is the disposal of spermatogenic cells by apoptosis and ovarian follicles by atresia. Cyclin‐dependent kinases (Cdks) and their cyclin partners coordinate the activities of the cell cycle. An additional cell‐cycle regulatory component is the centrosome. The centrosome harbors regulatory proteins controlling the normal progression of the cell cycle. Changes in individual centrosome proteins can lead to cell‐cycle arrest and a decrease in the genomic protective function of p53 that promotes apoptosis. Disruption of cyclin A1, Cdk2, and Cdk4 expression in transgenic mice results in infertility and gonadal atrophy. Cdk–cyclin complexes interact with regulatory proteins, which may fine‐tune the activities of the complex. One of the many regulatory proteins is p12, a 115 amino acid growth suppressor polypeptide designated p12CDK2AP1, partner of Cdk2 and with binding affinity to DNA polymerase α/primase. Overexpression of p12 is associated with testicular and ovarian atrophy without affecting fertility. Ectopic expression of p12 was driven by the keratin 14 promoter. Keratin 14 is the pairing partner of keratin 5 and both keratins are expressed in testis. The efficiency of keratin promoters in driving ectopic gonadal gene expression, the association of gonadal atrophy with the ectopic expression of a Cdk2 regulatory protein and the centrosome, as a reservoir of cell‐cycle regulatory proteins, open new experimental opportunities to address still lingering questions concerning cell differentiation and division during mammalian gametogenesis. Mol. Reprod. Dev. 939–942, 2006. © 2006 Wiley‐Liss, Inc.
Nerve‐terminal and Schwann‐cell response after nerve injury in the absence of nitric oxide
Authors: Marques Maria Julia , Pereira Elaine Cristina Leite , Minatel Elaine , Neto Humberto Santo
Published: May 2006

Dystrophic muscles show alterations in the dystrophin–glycoprotein complex and a lack of neuronal nitric oxide (NO) synthase. In mdx mice, presynaptic expression of neuronal NO synthase is decreased, suggesting that presynaptic signaling may be altered in dystrophic muscle. In this study, we examined the nerve‐terminal and Schwann‐cell responses after a crush lesion in control and NO‐deficient mice. Seven days after nerve crush, 24% of control neuromuscular junctions (n = 200) showed ultraterminal sprouts, whereas in NO‐deficient mice this frequency was 28.5% (n = 217; P > 0.05 compared to controls; chi‐square test). Schwann‐cell response did not change in the absence of NO, after a nerve lesion of 7‐day duration. Fourteen days after the lesion, nerve terminals sprouted and Schwann cells showed an extensive network of processes away from the synaptic site in controls. In the absence of NO, there was a dramatic decrease in nerve‐terminal sprouting and Schwann‐cell processes failed to extend away from the endplate. These results show that NO is involved in the nerve‐terminal and Schwann‐cell response to nerve injury. They also suggest that presynaptic molecular signaling may be impaired in dystrophic muscles, and this could influence the innervation and survival of newly formed myofibers generated by cell‐mediated therapies. Muscle Nerve, 2006
The one‐commodity pickup and delivery travelling salesman problem on a path or a tree
Authors: Wang Fan , Lim Andrew , Xu Zhou
Published: May 2006

Optimization algorithms for both path and tree topology classes of the one‐commodity pickup and delivery travelling salesman problem (1‐PDTSP) are proposed in this article, which focus on minimizing the route distance to transport products among pickup and delivery customers by a single vehicle with a limited capacity of k. Each pickup customer provides one unit volume of the product while each delivery customer requires one unit volume of the product. For the path case, we propose an O(n2/ min (k,n)) algorithm for any arbitrary k, and two O(n) algorithms for k = 1 and k = ∞. For the tree case, O(n2) and O(n) algorithms are proposed for k = 1 and k = ∞, respectively. Moreover, when k is arbitrary, the problem becomes NP‐hard in the strong sense. © 2006 Wiley Periodicals, Inc. NETWORKS, Vol. 48(1), 24–35 2006
A simple algorithm that proves half‐integrality of bidirected network programming
Authors: Bolker Ethan D. , Zaslavsky Thomas
Published: May 2006

In a bidirected graph, each end of each edge is independently oriented. We show how to express any column of the incidence matrix as a half‐integral linear combination of any column basis, through a simplification, based on an idea of Bolker, of a combinatorial algorithm of Appa and Kotnyek. Corollaries are that the inverse of each nonsingular square submatrix has entries 0,
$\pm{1\over 2}$, and ±1, and that a bidirected integral linear program has half‐integral solutions. © 2006 Wiley Periodicals, Inc. NETWORKS, Vol. 48(1), 36–38 2006
Minimizing false positives in kinase virtual screens
Authors: Perola Emanuele
Published: May 2006

In spite of recent improvements in docking and scoring methods, high false‐positive rates remain a common issue in structure‐based virtual screening. In this study, the distinctive features of false positives in kinase virtual screens were investigated. A series of retrospective virtual screens on kinase targets was performed on specifically designed test sets, each combining true ligands and experimentally confirmed inactive compounds. A systematic analysis of the docking poses generated for the top‐ranking compounds highlighted key aspects differentiating true hits from false positives. The most recurring feature in the poses of false positives was the absence of certain key interactions known to be required for kinase binding. A systematic analysis of 444 crystal structures of ligand‐bound kinases showed that at least two hydrogen bonds between the ligand and the backbone protein atoms in the kinase hinge region are present in 90% of the complexes, with very little variability across targets. Closer inspection showed that when the two hydrogen bonds are present, one of three preferred hinge‐binding motifs is involved in 96.5% of the cases. Less than 10% of the false positives satisfied these two criteria in the minimized docking poses generated by our standard protocol. Ligand conformational artifacts were also shown to contribute to the occurrence of false positives in a number of cases. Application of this knowledge in the form of docking constraints and post‐processing filters provided consistent improvements in virtual screening performance on all systems. The false‐positive rates were significantly reduced and the enrichment factors increased by an average of twofold. On the basis of these results, a generalized two‐step protocol for virtual screening on kinase targets is suggested. Proteins 2006. © 2006 Wiley‐Liss, Inc.
Molecular dynamics simulation of Leishmania major surface metalloprotease GP63 (leishmanolysin)
Authors: Bianchini Gianluca , Bocedi Alessio , Ascenzi Paolo , Gavuzzo Enrico , Mazza Fernando , Aschi Massimiliano
Published: May 2006

One of the molecular factors contributing to Leishmania sp. virulence and pathogenesis is the major surface metalloprotease GP63, alternatively called leishmanolysin, MSP, and PSP (EC 3.4.24.36). Here, the molecular dynamics simulation of Leishmania major GP63 in water at pH 7 is reported. Upon solvation, GP63 undergoes a sharp structural relaxation with respect to the crystal structure. The fluctuation pattern occurs essentially in solvent‐exposed nonstructured regions. By contrast, the active site turns out to be rigid. Essential dynamics and dynamic‐domain analyses, both carried out on the equilibrated portion of GP63, show that the fingerprint fluctuations of GP63 are practically characterized by the motion of a large part of the N‐terminal domain. These results appear to be in line with substrate recognition and (pro)enzyme activation played by the N‐terminal domain of GP63. A systematic analysis among a series of 10 homologs of GP63 also shows that the residues involved in the interdomain bending result highly conserved. This finding also suggests possible relationship between the maintainance of proteolytic activity and the similarity of the dynamical properties of the related enzymes. Proteins 2006. © 2006 Wiley‐Liss, Inc.
Enhancement‐mode AlGaN/GaN HEMTs on silicon substrate
Authors: Jia Shuo , Cai Yong , Wang Deliang , Zhang Baoshun , Lau Kei May , Chen Kevin J.
Published: May 2006

High performance enhancement‐mode AlGaN/GaN HEMTs (E‐HEMTs) were demonstrated with samples grown on low‐cost silicon substrate for the first time. The fabrication process is based on fluoride‐based plasma treatment of the gate region and post‐gate annealing at 450 °C. The fabricated E‐HEMTs have nearly the same peak transconductance (Gm) and cut‐off frequencies as the conventional depletion‐mode HEMTs (D‐HEMTs) fabricated on the same wafer, suggesting little mobility degradation caused by the plasma treatment. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth of InN on 6H‐SiC by plasma assisted molecular beam epitaxy
Authors: Brown April S. , Kim Tong‐Ho , Choi Soojeong , Wu Pae , Morse Michael , Losurdo Maria , Giangregorio Maria M. , Bruno Giovanni , Moto Akihiro
Published: May 2006

We have investigated the growth of InN films by plasma assisted molecular beam epitaxy on the Si‐face of 6H‐SiC(0001). Growth is performed under In‐rich conditions using a two‐step process consisting of the deposition of a thin, low‐temperature 350 °C InN buffer layer, followed by the subsequent deposition of the InN epitaxial layer at 450 °C. The effect of buffer annealing is investigated. The structural and optical evolution of the growing layer has been monitored in real time using RHEED and spectroscopic ellipsometry. Structural, morphological, electrical and optic properties are discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Capacitance characterization of AlN/GaN double‐barrier resonant tunnelling diodes
Authors: Kurakin A. M. , Vitusevich S. A. , Danylyuk S. V. , Naumov A. V. , Foxon C. T. , Novikov S. V. , Klein N. , Lüth H. , Belyaev A. E.
Published: May 2006

We report on the electrical characterization of AlN/GaN/AlN double‐barrier resonant tunnelling diodes (RTDs) using steady‐state current‐voltage and capacitance‐voltage (C‐V) characteristics in a wide frequency range with 2 kHz steps. The C‐V characteristics of a double‐barrier RTD show different behaviour under forward and reverse polarities and a strong dependence on frequency. The monotonous growth of capacitance at forward bias was registered, while a more complicated dependence was observed at reverse voltages. In order to analyse this dependence, a self‐consistent calculation of the potential profile of the structure was performed taking into account polarization effects at the AlN/GaN interfaces. The peculiarities are analysed in the model of possible charge trapping at the interface states. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
NH3/TMI molar ratio dependence of electrical and optical properties for atmospheric‐pressure MOVPE InN
Authors: Yamamoto A. , Miwa H. , Shibata Y. , Hashimoto A.
Published: May 2006

The electrical and optical properties for atmospheric‐pressure MOVPE InN have been studied as a function of NH3/TMI molar ratio during the growth. Residual carrier (electron) concentration is decreased with increasing NH3/TMI molar ratio. PL peak energy is also shifted to a low energy side with increasing NH3/TMI molar ratio. Hall mobility of InN is almost independent on NH3/TMI molar ratio and is rather decreased at a high NH3/TMI molar ratio. The highest mobility is obtained for a sample grown at a relatively low NH3/TMI molar ratio. The grain size of the InN films is decreased with increasing NH3/TMI molar ratio. The lowest carrier concentration of 4.5×1018 cm–3 and highest mobility of 1100 cm2/Vs obtained here are the best data for MOVPE InN ever reported. Based on these results, the most probable candidate for donors and the dominant carrier‐scattering mechanism for atmospheric‐pressure MOVPE InN are discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigations on local Ga and In incorporation of GaInN quantum wells on facets of selectively grown GaN stripes
Authors: Neubert B. , Habel F. , Brückner P. , Scholz F. , Schirra M. , Feneberg M. , Thonke K. , Riemann T. , Christen J. , Beer M. , Zweck J. , Moutchnik G. , Jetter M.
Published: May 2006

Multiple GaInN quantum wells (QWs) were grown on side facets with reduced piezoelectric fields (PFs) of selectively grown GaN stripes oriented along the 〈1$ \bar 1 $00〉 and 〈11$ \bar 2 $0〉 directions by metalorganic vapor phase epitaxy (MOVPE). The different luminescence wavelengths observed for the QWs on these facets can be explained by the reduced PFs, additionally the QW thickness depends on the facet type. Although stripes running along 〈1$ \bar 1 $00〉 and 〈11$ \bar 2 $0〉 develop similar triangular or trapezoidal shape, their detailed growth behaviour, electrical and luminescence properties differ significantly pointing to different adsorption/desorption and inter‐facet migration processes of In, Ga and the p‐type dopant Mg. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Suppression of gate leakage current in GaN MOS devices by passivation with photo‐grown Ga2O3
Authors: Wu H.‐M. , Peng L.‐H.
Published: May 2006

We report the use of photo‐enhanced chemical (PEC) technique to form high‐quality metal oxide semiconductor (MOS) devices made of gallium oxide (Ga2O3)/gallium nitride (GaN). Gate leakage current density as low as 2×10–7 A/cm2 at a bias field up to 2 MV/cm is observed in the GaN MOS devices that are formed by novel PEC wet etching and have the top surface and mesa sidewall passivated by the photo‐grown Ga2O3. The depth‐resolved X‐ray photo‐emission spectra (XPS) and atomic‐ratio analysis indicate that a intermediate and thin ∼20 nm GaON layer of graded composition forms the Ga2O3/GaON/GaN system, which releases the interfacial strain and thus minimizes the density of interfacial states. The IV and high‐frequency CV analyses reveal that the Ga2O3 layer can sustain an electrical breakdown field of 3.5 MV/cm and the structures have a low density of interfacial state (Dit) in the order of 1011 eV–1cm–2. We attribute these results to the immunity to surface damage by the novel PEC wet etching and the effective passivation on mesa sidewall and surface formed by the photo‐grown Ga2O3. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Enhanced emission efficiency of InGaN films with Si doping
Authors: Li Da‐Bing , Liu Yu‐Huai , Katsuno Takuya , Nakao Keisuke , Nakamura Kazuya , Aoki Masakazu , Miyake Hideto , Hiramatsu Kazumasa
Published: May 2006

High emission efficiency of InGaN films were obtained with Si doping, and the influence of Si doping on structural and optical properties of InGaN epilayers with different Si concentration were investigated in detail by means of high‐resolution X‐ray diffraction (HRXRD), scanning electron microscope (SEM), Cathodoluminescence (CL) and photoluminescence(PL). V‐defects were observed on the surface of InGaN films, and further investigation by CL showed that V‐defects act as nonradiative center, which lower the emission efficiency of InGaN. Meanwhile, it was found that Si doping could improve the crystal quality of InGaN and suppress the formation of V‐defects in InGaN, and hence enhance the emission efficiency of InGaN. One possible mechanism of influence of Si doping on the formation of V‐defects in InGaN was also proposed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Improvement of luminous intensity of InGaN light emitting diodes grown on hemispherical patterned sapphire
Authors: Lee Jae‐Hoon , Oh Jeong‐Tak , Park Jin‐Sub , Kim Je‐Won , Kim Yong‐Chun , Lee Jeong‐Wook , Cho Hyung‐Koun
Published: May 2006

To improve the external quantum efficiency, high quality GaN film was grown on hemispherical patterned sapphire by controlling the V/III ratio during the initial growth stage. The luminous intensity of white flash light emitting diode (LED) grown on hemispherical patterned sapphire (HPS) was estinated to be 5.8 cd at a forward current of 150 mA, which is improved by 20% more than that of LED grown on conventional sapphire substrate. The improvement of luminous intensity was explained by considering not only an increase of the extraction efficiency via the suppressed total internal reflection at the corrugated interface but also a decrease of dislocation density. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dislocation behaviour in III‐nitride epitaxial films grown on vicinal sapphire (0001) substrates
Authors: Shen X. Q. , Matsuhata H. , Okumura H.
Published: May 2006

Dislocation behaviour in AlN and GaN films grown on vicinal sapphire (0001) substrates are investigated using transmission electron microscopy. It is found that the dislocation behaviours strongly depend on the vicinal angle of the substrates. When the vicinal angle is 0.5°, the dislocation lines propagate along the c‐axis and no bending of the dislocation line is found. On the other hand, dislocation bending occurs in the films grown on the 2.0°‐off substrates, which results in the great reduction of the dislocation density in the films. The dislocation loop formation and the combination of two dislocations into one are the main mechanisms for this reduction. The surface morphology (mono‐layer and multilayer step formations) plays an important role in determining the different dislocation behaviours. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of optical‐output‐power degradation in 365‐nm UV‐LEDs
Authors: Mukai Takashi , Morita Daisuke , Yamamoto Masashi , Akaishi Kazuyuki , Matoba Kousuke , Yasutomo Katsuhiro , Kasai Yoshio , Sano Masahiko , Nagahama Shin‐ichi
Published: May 2006

The dependence of UV‐LED lifetime on threading dislocation density(TDD) was examined. UV‐LED structures were grown on standard GaN template(TDD: 1x108/cm2) and ELO‐GaN(TDD: 1x107/cm2), and lifetime testing was performed under a forward current of 500 mA at junction temperature(Tj) of 75 ºC. Lifetime of both LEDs were estimated as 17,600 h (standard GaN template) and 166,000 h (ELO‐GaN), respectively. It was found that GaN underlying layer with TD‐density of 1x107/cm2 is superior to that of 1x108/cm2 in terms of LED lifetime, despite no output power difference. Junction temperature (Tj) dependence of LED lifetime was investigated in use of standard GaN template(1x108/cm2). Tj was varied from 311 K to 422 K. The activation energy was determined to be 0.36 eV. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
InGaN blue cathodoluminescence phosphors synthesized with long reaction time in a new reactor
Authors: Kanie Hisashi , Kobayashi Shingo , Sema Yuji
Published: May 2006

InGaN microcrystals were grown by two‐stage growth method for 10 hours in a new reactor without clogging an exhaust tube by fine particles. Obtained InGaN showed double peaked cathodoluminescence spectra, violet peak at 385‐389 nm and blue at 438‐444 nm when excited at 5‐15 kV. The uniformity of the blue emission spectra among the crystals were improved for those grown for the 10‐hour reaction time. The yields of emissive GaN and InGaN crystals were not improved. The compatibility of the position of the violet band of the InGaN crystals to that of the GaN crystals and the resemblance of morphology of the GaN and InGaN crystals imply the growth of InGaN on GaN facets in two‐stage growth. The cause of the deterioration of the CL efficiency of the grown InGaN crystals at a low acceleration voltage was discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
InGaN‐based light‐emitting diodes grown on grooved sapphire substrates
Authors: Wang Wei‐Kai , Wuu Don‐Sing , Lin Shu‐Hei , Huang Shih‐Yung , Horng Ray‐Hua
Published: May 2006

We investigate the microstructure and electrical properties of the InGaN‐based light‐emitting diodes (LEDs) fabricated onto patterned sapphire substrates (PSSs) with parallel grooves. The PSS with parallel grooves (ridge: 3 μm; trench: 2 μm) along the (11‐20) direction were etched using an inductively‐coupled‐plasma etcher with different etching depths. It was found that the threading dislocation density in the GaN epilayer can be effectively reduced by the present PSS technique as indicated from the transmission‐electron‐microscopy result. For a typical lamp‐form PSS LED operating at a forward current of 20 mA, the output power and external quantum efficiency were measured to be 7.1 mW and 10.1%, respectively. The achieved improvement of the output power is not only due to the improvement of the internal quantum efficiency upon decreasing the dislocation density, but also due to the enhancement of the extraction efficiency using the PSS. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Raman scattering from In0.2Ga0.8N/GaN superlattices
Authors: Kisoda Kenji , Hirakura Kohji , Harima Hiroshi
Published: May 2006

We have performed Raman scattering experiments on high quality In0.2Ga0.8N/GaN superlattices(SLs). The A1 LO phonon mode from the In0.2Ga0.8N layer was observed in the Mg doped SL. This was attributable to manifestation of a resonance enhancement via acceptor levels formed by magnesium doping. The peak frequency of the A1 LO mode shifted to high frequency side with the excitation energy. The frequency shift suggested that the composition of indium was fluctuated along the growth direction in the InGaN layer. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Broadband spectrally dynamic solid state illumination source
Authors: Nicol David B. , Asghar Ali , Gupta Shalini , Kang Hun , Pan Ming , Strassburg Martin , Summers Chris , Ferguson Ian T.
Published: May 2006

Solid state lighting has done well recently in niche markets such as signage and displays, however, no available SSL technologies incorporate all the necessary attributes for general illumination. Development of a novel solid state general illumination source is discussed here. Two LEDs emitting at two distinct wavelengths can be monolithically grown and used to excite two or more phosphors with varied excitation spectra. The combined phosphorescence spectrum can then be controlled by adjusting the relative intensities of the two LED emissions. Preliminary phosphor analysis shows such a scheme to be viable for use in a spectrally dynamic broadband general illumination source. A tunnel junction is envisioned as a means of current spreading in a buried layer for three terminal operation. However, tunnel junction properties in GaN based materials are not well understood, and require further optimization to be practical devices. Preliminary results on GaN tunnel junctions are presented here as well. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Local structural characterization of epitaxial a ‐plane InGaN/GaN thin films by transmission electron microscopy
Authors: Yamazaki T. , Kusakabe K. , Nakanishi N. , Ohkawa K. , Hashimoto I.
Published: May 2006

Structural analysis of the submicron area of an InGaN thin film was conducted using transmission electron microscopy. By obtaining the selected area diffraction patterns of c ‐plane InGaN/GaN and a ‐plane InGaN/GaN films, the local lattice parameters were measured. Coherent growths were checked at the respective samples for different growth orientations, and the In concentration of the InGaN layer was also measured. Furthermore, there is a slight tilt in the growth direction between the GaN and InGaN layers in the a ‐plane InGaN/GaN film. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of the Nile Red spectra by semi‐empirical calculations and spectrophotometric measurements
Authors: Dias Lauro C. , Custodio Rogério , Pessine Francisco B. T.
Published: May 2006

The spectroscopic behavior of Nile Red (NR) in solutions was investigated by spectrophotometric measurements and was calculated with the semi‐empirical intermediate neglect of differential overlap for spectroscopy (INDO/S) method. Two parametrizations implemented, respectively, by Pople and by Da Motta and Zerner, were employed; the solvent effects were simulated according to the dielectric continuum model [self‐consistent reaction field (SCRF)], as well as with the explicit inclusion of solvent molecules. The calculations simulated reasonably well the experimental spectra and the intense solvatochromism of NR because the dipole moments were calculated to be higher in the first excited state than in the ground state. In addition, INDO/S calculations were carried out for partially optimized twisted conformers, whose electron donor moiety was orthogonal to the aromatic acceptor one and charge transfer was observed for excited states known as twisted intramolecular charge‐transfer (TICT) states. In polar media, INDO/S+SCRF calculations drastically stabilized the TICT state, reducing its energy down to the first excited state. Despite this intense solute–solvent stabilization, it is still less stable than the first excited state of the nontwisted, fully optimized conformer, and the limitations of the semi‐empirical methods could not predict its role, if any, on the spectroscopic behavior of NR, except for the fact that the solvatochromism was explained independent of its presence. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
Singlet–triplet gaps and insertion reactions of aminocyanocarbenes: A computational study of hydrogen cyanide covalent dimers
Authors: Freeman Fillmore , Gomarooni Mahshid
Published: May 2006

Singlet–triplet gaps (S–T, ΔEST), structural parameters, intramolecular CH insertion reactions, intramolecular NH insertion reactions, intermolecular CH insertion reactions, and intramolecular 1,2‐rearrangements of aminocyanocarbenes (NCCNX2, X = H, CH3, CF3) have been studied using restricted and unrestricted CCD, CCSD, QCISD, B3LYP, and MP2 methods with the 6‐31G(d), 6‐311+G(d,p), cc‐pVDZ, and cc‐pVTZ basis sets. HCNH2, NCCNH2, NCCN(CH3)2, and NCCN(CF3)2 have singlet ground states. The ΔEST values for aminocyanocarbene, N,N‐(dimethylamino)cyanocarbene, and N,N‐(ditrifluoromethylamino)cyanocarbene are 29.34, 32.75, and 19.48 kcal/mol, respectively. Aminocyanocarbene, a hydrogen cyanide covalent dimer, is predicted to have higher energy than the dimer (Z)‐C‐cyanomethanimine which is lower in energy than the isomeric (E)‐C‐cyanomethanimine and N‐cyanomethanimine. The three‐centered transition state connecting singlet aminocyanocarbene with (Z)‐C‐cyanomethanimine is 55.7 kcal/mol higher in energy than the carbene and the transition state connecting the E and Z isomers of C‐cyanomethanimine is 29.54 kcal/mol higher in energy than the Z isomer. CCSD/cc‐pVDZ predicted the barrier for the intermolecular insertion of singlet aminocyanocarbene into a CH bond of methane to be 35.40 kcal/mol. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
Orbital interactions and charge redistribution in weak hydrogen bonds: Watson–Crick GC mimic involving CH proton donor and F proton acceptor groups
Authors: Guerra Célia Fonseca , Baerends Evert Jan , Bickelhaupt F. Matthias
Published: May 2006

The discovery by Kool and coworkers that 2,4‐difluorotoluene (F) mimics thymine (T) in DNA replication has led to controversy regarding the question of whether this mimic has the capability of forming hydrogen bonds with adenine (A). Recently, we have provided evidence for an important role of both hydrogen bonding and steric effects in the replication of DNA. In the present work, we extend our study to mimics (GFC′N′and CN′NF) of the bases guanine (G) and cytosine (C). We address not only the question of the strengths of the hydrogen bonds in GFC′N′CN′NFas compared with those in GC but we focus in particular on the nature of these interactions. Thus, we have analyzed GFC′N′CN′NFand GC at the BP86/TZ2P level of density functional theory (DFT). In line with previous experience, this approach is shown to achieve close agreement with the available data from ab initio computations and experiment: the complexation energy of GFC′N′CN′NF(‐4.1 kcal/mol) is confirmed to be much weaker indeed than that of GC (‐26.1 kcal/mol). Interestingly, the weak hydrogen bonds in GFC′N′CN′NFstill poses a significant orbital interaction component that resembles the situation for the more strongly bound GC, as follows from (1) an analysis of the orbital electronic structure of GFC′N′CN′NFand GC, (2) a quantitative decomposition of the GFC′N′CN′NFand GC bond energies, as well as (3) a quantitative decomposition of the charge redistribution associated with the GFC′N′ CN′NFand GC interactions based on the Voronoi deformation density (VDD) method. The VDD method allows us to decompose the charge redistribution ΔQper atom into a component associated with the Pauli repulsive orbital interactions and a component associated with the bonding orbital interactions: ΔQ= ΔQPauli+ ΔQoi. Implications of our findings for the mechanism of DNA replication are discussed. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
Gauss–Bessel quadrature: A tool for the evaluation of Barnett–Coulson/Löwdin functions
Authors: Bouferguene Ahmed , Safouhi Hassan
Published: May 2006

In previous work, we analyzed the numerical efficiency of several algorithms that can be used to evaluate the so‐called Barnett–Coulson/Löwdin functions (BCLFs). It was shown that series representations of these functions are generally not recommended in the neighborhood of the cusp because of their poor convergence (logarithmic convergence). In the present work, we propose to evaluate BCLFs using its symmetric integral representation combined with a tailored Gauss quadrature. The new method is shown to be capable of achieving acceptable accuracy, as illustrated by the numerical values obtained for two‐center overlap integrals, which agree with previously published results. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
Analysing capture–recapture data when some variables of heterogeneous catchability are not collected or asked in all registrations
Authors: Zwane Eugene N. , van der Heijden Peter G. M.
Published: May 2006

Registrations in epidemiological studies suffer from incompleteness, thus a general consensus is to use capture–recapture models. Lately, there has been a thrust to incorporate covariates which relate to the capture probabilities in order to improve the estimate of population size. Current approaches utilize covariates observed in all the pertinent registrations. In epidemiological applications, one often encounters capture–recapture data where some covariates are measured by some but not by all of the registrations under scrutiny. In this article, the usefulness of these types of covariates is evaluated and furthermore a methodology for analysing such capture–recapture data is presented. The methodology is illustrated by applying it to data on neural tube defects in the Netherlands. Copyright © 2006 John Wiley & Sons, Ltd.
Variable selection and raking in propensity scoring
Authors: Judkins David R. , Morganstein David , Zador Paul , Piesse Andrea , Barrett Brandon , Mukhopadhyay Pushpal
Published: May 2006

This paper discusses some practical issues in applying propensity scoring in the context of endpoint analysis in a pre‐/posttest longitudinal design with an ordinal measure of treatment intensity and a high‐dimensional potential covariate space: how many covariates to include in propensity models; how to evaluate the adequacy of tentative propensity models; and how to tailor models to provide hypercontrol on a limited subset of covariates. These issues arose in the evaluation of a health communication program. Copyright © 2006 John Wiley & Sons, Ltd.
Social Democracy and Active Labour-Market Policies: Insiders, Outsiders and the Politics of Employment Promotion
Authors: RUEDA DAVID
Published: May 2006

Active labour-market policy is an important tool for governments interested in the promotion of employment. This article explores a topic in the comparative political economy literature in need of more attention: the politics behind the promotion of active labour policies. It is argued here that social democratic governments are often not interested in employment promotion measures; labour is divided into those with secure employment (insiders) and those without (outsiders); it is contended that social democratic governments have strong incentives to pursue labour-market policies that benefit insiders but not outsiders. There are factors, however, that either exacerbate or limit the effects of insider–outsider differences on social democracy. These claims are tested in three ways. First, the interplay of government partisanship and employment protection is explored in the British case. Secondly, the individual preferences assumed in the model are tested with Eurobarometer data. And thirdly, the effects of social democracy on active labour-market policy are analysed using data from sixteen industrialized democracies.
Voter Strategies with Restricted Choice Menus
Authors: BENOIT KENNETH , GIANNETTI DANIELA , LAVER MICHAEL
Published: May 2006

Mixed-member electoral systems require voters simultaneously to cast ballots in single-member districts (SMD) and multimember, proportional representation (PR) constituencies. It may be that not all parties offer candidates in both electoral contexts, however. In this event would-be voters for some parties may find themselves ‘frustrated’ by the restricted choice menu on offer in the SMD, being effectively forced to split their vote between different parties. Here we explore the different behaviours of frustrated voters in the 1996 mixed-member election to Italy's Chamber of Deputies, characterizing these as being either in some sense non-strategic (concerned above all with the relative policy platforms of candidates) or strategic (concerned above all to influence the eventual composition of government). Using an extended method for ecological inference, we parameterize and estimate rates of different types of ticket-splitting at the district level, and link the degree of what we characterize as strategic voting to the relative policy distance between the respective local representatives of the Italian pre-electoral coalitions.
The Attrition Game: Initial Resources, Initial Contests and the Exit of Candidates During the US Presidential Primary Season
Authors: NORRANDER BARBARA
Published: May 2006

In contests for the presidential nominations from the Democratic and Republican parties in the United States, the duration of candidacies determines both the winning candidate (i.e., the one who outlasts his or her opponents) and the amount of intraparty conflict before the nomination is bestowed. This article analyses how strategic considerations lead some candidates to exit the race more quickly than others. Factors which could shape such strategic considerations include initial candidate assets and characteristics (national poll standings, fund-raising totals and occupational background), initial contest outcomes (Iowa and New Hampshire) and structural variables (proportional representation delegate distribution rules, party, front-loaded calendar). Results from a duration model indicate that poll standings, money (in a curvilinear pattern), New Hampshire and Iowa results, occupational backgrounds and the front-loading of the primary calendar shaped the length of candidacies for presidential contestants from 1980 to 2004. Candidates lacking in initial assets or early victories leave the nomination race in a process most resembling a game of attrition.
On the Interconnectedness of Regulatory Policy and Markets: Lessons from Banking
Authors: BERNAUER THOMAS , KOUBI VALLY
Published: May 2006

Capital requirements are an important regulatory device for the management of systemic risk in the banking industry. A puzzling fact is the existence of widespread over-compliance of banks regarding national and international regulatory capital requirements. Some light is shed on this pattern by studying bank capitalization decisions using 1,267 banks from twenty-nine OECD countries. The effect of market pressure (competition) on bank capitalization is found to be positive, whereas the direct effect of regulation is ambiguous. Three points can be made. First, the effectiveness of regulation must be evaluated taking into account the – often overlooked – indirect effects. Secondly, the impact of regulation can be amplified by competitive forces when there are synergies between regulatory and market pressures. Such synergies seem to have played a key role in the widespread adoption and effectiveness of international regulatory capital requirements (the Basle Accord). And thirdly, the prospects for international regulatory convergence in any area are influenced by the interconnectedness (synergies vs. rivalries) between regulatory and market processes.
Arab Behaviour Towards Israel: Strategic Avoidance or Exploiting Opportunities?
Authors: DEROUEN KARL , SPRECHER CHRISTOPHER
Published: May 2006

Scholars often observe that the foreign policies of states are not made in a vacuum but rather are determined or moulded to a significant degree by the external and internal actions of rivals. Domestic unrest is often considered a potential impetus for changing strategic behaviour. Leaders may be tempted to employ force externally to divert attention away from domestic unrest. The intended result is a ‘rally round the flag’ effect that culminates in higher approval/support for the executive as citizens forget about domestic problems and pay attention to a common adversary. One implication of this sort of ‘diversion’ is that potential scapegoats might employ strategic behaviour to avoid becoming a diversionary target. In other words, when they witness domestic unrest in a rival state, they worry that the rival may lash out at them and thus engage in ‘strategic avoidance’.

Conversely, strategic behaviour may lead to a greater chance that the potential ‘diverter’ will itself be targeted for hostile behaviour. Erstwhile scapegoats may view periods of social unrest such as elections, domestic political protests or unstable cabinet structures in the other country as convenient and favourable times to escalate hostility. Such situations are viewed as opportunities that are ripe for exploitation.

Alastair Smith's work has been extended to both the US case and a comparative cross-national study. Our purpose here is to extend this line of inquiry by looking at a region of the world locked in a long-term hostile relationship; namely, the Middle East. Our approach builds upon previous research that addresses the strategic interaction of enduring rivals.