bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonlinear ultrasonics for in situ damage detection during high frequency fatigue
Authors: Kumar Anish , Torbet Christopher J. , Jones J. Wayne , Pollock Tresa M.
Published: July 2009

In this paper, we report the use of the feedback signal of an ultrasonic fatigue system to dynamically deduce fatigue damage accumulation via changes in the nonlinear ultrasonic parameter. The applicability of this parameter in comparison to the resonant frequency for assessment of fatigue damage accumulation in a wrought aluminum alloy has been demonstrated, without the need for coupling fluids or independent generation of incident ultrasonic waves. The ultrasonic nonlinearity increased and the resonant frequency of the system decreased with initiation and propagation of the major crack. The nonlinear ultrasonic parameter shows greater sensitivity to damage accumulation than the resonant frequency. The number of cycles for crack propagation, estimated based on the changes in the nonlinear ultrasonic parameter, is in very good agreement with calculated crack growth rates based on the fractography studies.
Mechanism of carbon nanotubes unzipping into graphene ribbons
Authors: Rangel Norma L. , Sotelo Juan C. , Seminario Jorge M.
Published: July 2009

The fabrication of graphene nanoribbons from carbon nanotubes (CNTs) treated with potassium permanganate in a concentrated sulfuric acid solution has been reported by Kosynkin et al. [Nature (London) 458, 872 (2009)]. Here we report ab initio density functional theory calculations of such unzipping process. We find that the unzipping starts with the potassium permanganate attacking one of the internal C–C bonds of the CNT, stretching and breaking it. The created defect weakens neighboring bonds along the length of the CNT, making them energetically prone to be attacked too.
Ice friction: The effects of surface roughness, structure, and hydrophobicity
Authors: Kietzig Anne-Marie , Hatzikiriakos Savvas G. , Englezos Peter
Published: July 2009

The effect of surface roughness, structure, and hydrophobicity on ice friction is studied systematically over a wide range of temperature and sliding speeds using several metallic interfaces. Hydrophobicity in combination with controlled roughness at the nanoscale is achieved by femtosecond laser irradiation to mimic the lotus effect on the slider’s surface. The controlled roughness significantly increases the coefficient of friction at low sliding speeds and temperatures well below the ice melting point. However, at temperatures close to the melting point and relatively higher speeds, roughness and hydrophobicity significantly decrease ice friction. This decrease in friction is mainly due to the suppression of capillary bridges in spite of the presence of surface asperities that facilitate their formation. Finally, grooves oriented in the sliding direction also significantly decrease friction in the low velocity range compared to scratches and grooves randomly distributed over a surface.
Band engineered epitaxial Ge–SixGe1−x core-shell nanowire heterostructures
Authors: Varahramyan K. M. , Ferrer D. , Tutuc E. , Banerjee S. K.
Published: July 2009

We report the growth of germanium (Ge)—silicon-germanium (SixGe1−x) epitaxial core-shell nanowire (NW) heterostructures, with tunable Si and Ge shell content. The Ge NWs are grown using the vapor-liquid-solid growth mechanism, and the SixGe1−x shells are grown in situ, conformally on the Ge NWs using ultrahigh vacuum chemical vapor deposition. We use transmission electron microscopy to demonstrate epitaxial shell growth, and scanning energy dispersive x-ray spectroscopy to determine the shell thickness and content. The Si and Ge shell content can be tuned depending on the SiH4 and GeH4 partial pressures during the shell growth, enabling band engineered core-shell NW heterostructures.
Study of electrical characterization of 2-methyl-9, 10-di(2-naphthyl)anthracene doped with tungsten oxide as hole-transport layer
Authors: Hsieh Ming-Ta , Ho Meng-Huan , Lin Kuan-Heng , Chen Jenn-Fang , Chen Teng-Ming , Chen Chin H.
Published: July 2009

An efficient p-doped transport layer composed of an ambipolar material, 2-methyl-9,10-di(2-naphthyl)anthracene (MADN) and tungsten oxide (WO3) has been developed. The admittance spectroscopy studies show that the incorporation of WO3 into MADN can greatly improve the hole injection and the conductivity of the device. Moreover, when this p-doped layer was incorporated in the tris(8-quinolinolato)aluminum-based device, it achieved a current efficiency of 4.0 cd/A and a power efficiency of 2.4 lm/W at 20 mA/cm2. This work paves the way to simplify the fabrication of future p-i-n organic light-emitting devices with a single common ambipolar MADN material.
Electrical behavior of AlGaN/GaN heterostuctures upon high-temperature selective oxidation
Authors: Roccaforte F. , Giannazzo F. , Iucolano F. , Bongiorno C. , Raineri V
Published: July 2009

In this paper, the influence of a high-temperature (900 °C) selective oxidation process on the electrical properties of AlGaN/GaN heterostructures was investigated. In particular, electrical measurements performed on appropriate devices and test patterns demonstrated that the current flow through the two-dimensional electron gas (2DEG) was suppressed, even if the thickness of the local oxide did not reach the AlGaN/GaN interface. The combination of macroscopic current-voltage and capacitance-voltage measurements with depth-resolved scanning capacitance microscopy elucidated the doping dependence and the compositional stability of the material during high-temperature oxidation. The reduction in the 2DEG sheet carrier density and the variation of the threshold voltage of simple high electron mobility transistor structures upon high-temperature annealing were also discussed.
Nanodesign of superhydrophobic surfaces
Authors: Ramos S. M. M. , Canut B. , Benyagoub A.
Published: July 2009

When deposited on a hydrophobic rough surface, a small water drop looks like a small pearl. In this study we investigate the conditions to observe such a phenomenon when the roughness of the substrate, of fractal nature, consists of nanofeatures obtained by the ion track etching technique. The surface roughness was characterized by two parameters: the fractal dimension Df and the aspect ratio AR. Both were extracted from the analysis of atomic force microscopy images and were directly correlated with the etching time. Df is found in the interval of 2.46–2.69, while AR varies from 0.5 to ∼15. We show that for the highest Df values the water contact angles on these surfaces can exceed 150°, while the hysteresis—the difference between the advancing and receding contact angles—is reduced to 4–5°. Superhydrophobic surfaces can thus be obtained and this property seems well controlled by the fractal dimension, which is itself controlled by the ion track etching process. Furthermore, the experimental results are well described by the wetting theory, and it is shown that superhydrophobicity of these surfaces results from a single-scale roughness of nanometric size.
Emitting-layer design of white organic light-emitting devices with single-host material
Authors: Hsiao Chih-Hung , Lee Jiun-Haw
Published: July 2009

Efficient phosphorescence sensitization (PS) consisting of tris(phenylpyridine)iridium (Ir(ppy)3) sensitizers and 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran) (DCJTB) exciton acceptors in a host material, N,N′-dicarbazolyl-3,5-benzene, was implemented by a simplified emitting-layer structure with selectively doped DCJTB in the Ir(ppy)3-doped region. This codoped region away from the recombination zone peak in the Ir(ppy)3-doped region significantly improved the PS efficiency without affecting the carrier transport characteristics. Coupled with an efficiently phosphorescent blue emitter, iridium(III)bis[(4,6-di-fluoropheny)- pyridinato-N,C2′]picolinate, a white organic light-emitting device utilizing this PS approach was demonstrated to have 10.94% external quantum efficiency, 17.4 cd/A and 12.2 lm/W at an applied voltage of 4.5 V, and a brightness of 107 cd/m2 with Commission Internationale de l'Eclairage coordinates of (0.293, 0.427). With a 3 nm spacer for manipulating the exciton diffusion in the emitting layer, a slight CIE coordinates variation of (−0.008, −0.006) was obtained at practical luminance levels of 1000–4000 cd/m2, evidence that PS was successfully achieved.
Plasma uniformity and phase-controlled etching in a very high frequency capacitive discharge
Authors: Sung Dougyong , Woo Jehun , Lim Kyungchun , Kim Kyungsun , Volynets Vladimir , Kim Gon-Ho
Published: July 2009

The influence of controlled phase shift between very high frequency (100MHz) voltages applied to the powered electrodes on the plasma uniformity and etch rate was studied in a capacitive triode-type reactor. Radial profiles of plasma optical emission were measured as a function of the phase shift in process (C4F8∕O2∕Ar) plasma with the low frequency bias power both turned off and on. Radial profiles of KrF photoresist etch rate over a 300mm wafer were obtained in the same conditions (with the bias power turned on). Besides, plasma density at the wafer center and edge was measured versus the phase shift in pure Ar plasma. It occurred that all measured characteristics strongly depend on the phase shift and correlate with each other. It has been shown that the phase-shift control can considerably improve both the plasma and etch-rate uniformity in very high-frequency capacitive reactors.
Charged particle reflection from an artificially structured boundary that produces a spatially periodic magnetostatic field
Authors: Ordonez C. A.
Published: July 2009

Charged particle reflection away from an artificially structured boundary is studied by computer simulation. The artificially structured boundary produces a spatially periodic static magnetic field such that the spatial period of the field is much smaller than the dimensions of a source of incident charged particles. A planar artificially structured boundary comprised of a sequence of parallel wires is considered. The wires carry currents in alternating directions and produce the magnetic field. A classical trajectory Monte Carlo study is reported. The motion of charged particles that approach the artificially structured boundary at small or grazing angles of incidence transverse to the wires is simulated. The conditions under which the charged particles reflect away from the boundary without reaching it are determined, and the results are fit to obtain analytical expressions. The results are not dependent on the sign of charge of the incident particles.
Growth, magnetic properties, and Raman scattering of La2NiMnO6 single crystals
Authors: Iliev M. N. , Gospodinov M. M. , Singh M. P. , Meen J. , Truong K. D. , Fournier P. , Jandl S.
Published: July 2009

Millimeter size single crystals of double-perovskite La2NiMnO6 were grown by the high-temperature solution growth method. The magnetic measurements and polarized Raman spectra between 5 and 350 K provide evidence that the crystals have a high degree of Ni2+/Mn4+ ordering, a small amount of lattice defects, and the highest Tc=288 K reported so far for ferromagnetic double perovskites. At a microscopic level, the crystals are heavily twinned, and the effect of twinning on the Raman spectra is analyzed in detail.
Role of gate oxide thickness in controlling short channel effects in polycrystalline silicon thin film transistors
Authors: Valletta A. , Gaucci P. , Mariucci L. , Pecora A. , Cuscunà M. , Maiolo L. , Fortunato G. , Brotherton S. D.
Published: July 2009

The drain bias induced threshold voltage variation in short channel (L=0.4 μm) polycrystalline silicon thin-film transistors (TFTs), with different gate oxide thicknesses, is investigated with combined experimental measurements and numerical simulations. Drain-induced barrier lowering (DIBL) and floating body effects (FBEs), triggered by impact ionization, are the main causes of such variations. However, the effects are counterbalancing, with a reducing oxide thickness reducing DIBL, while, at the same time, increasing the relative impact of the FBE. Hence, drain bias induced threshold voltage changes, when normalized by oxide thickness, are independent of the gate oxide thickness in these TFTs.
Self-organized (Ba0.7,Sr0.3)TiO3 nanocomposite with improved figure of merit
Authors: Guigues B. , Zhu X. H. , Sobotka J. , Guiblin N. , Defaÿ E. , Dkhil B.
Published: July 2009

Self-organized (Ba0.7,Sr0.3) TiO3 (BST) thin film nanocomposites with spherical inclusions have been fabricated. The composite structures were built up from initial amorphous BST films, thanks to an adequate thermal treatment. Microstructural and electrical analyses are reported as a function of crystallization ratio q. Our experimental results agree with recently developed models of composite materials. The main conclusion of the study is that high dielectric performances can be obtained with a half-crystallized material. For a 630 °C annealing temperature (q-ratio equal to 0.47), Vendik commutation quality factor reaches 1500, which is two times greater than a fully crystallized sample annealed at 700 °C.
A new formulation and simplified derivation of the dispersion function for a plasma with a kappa velocity distribution
Authors: Mace R. L. , Hellberg M. A.
Published: July 2009

A simplified derivation of the relationship between the dispersion function for a plasma with a kappa velocity distribution and the Gauss hypergeometric function is presented. This derivation relies on only a few standard integrals. It naturally leads to a new integral representation for the dispersion function, which readily yields the power and Laurent series for it. The new integral representation is shown to be closely related to the Gordeyev integral for a kappa distribution.
Transition from ferromagnetism to diamagnetism in undoped ZnO thin films
Authors: Kapilashrami Mukes , Xu Jun , Ström Valter , Rao K. V. , Belova Lyubov
Published: July 2009

We report a systematic study of the film thickness dependence (0.1–1 μm) of room-temperature ferromagnetism in pure magnetron-sputtered ZnO thin films wherein a sequential transition from ferromagnetism to paramagnetism and diamagnetism as a function of film thickness is observed. The highest saturation magnetization (MS) value observed is 0.62 emu/g (0.018 μB/unit cell) for a ∼480 nm film. On doping the ZnO film with 1 at. % Mn enhances the MS value by 26%. The ferromagnetic order in ZnO matrix is believed to be defect induced. In addition, on doping with Mn hybridization between the 2p states of O and the 3d states of Mn occurs.
Gas phase and bulk ultraviolet photoemission spectroscopy of 3,4,9,10-perylene-tetracarboxylic dianhydride, 1,4,5,8-naphthalene-tetracarboxylic dianhydride, and 1,8-naphthalene-dicarboxylic anhydride
Authors: Sauther J. , Wüsten J. , Lach S. , Ziegler Ch.
Published: July 2009

The π-conjugated organic molecules 3,4,9,10-perylene-tetracarboxylic dianhydride, 1,4,5,8-naphthalene-tetracarboxylic dianhydride, and 1,8-naphthalene-dicarboxylic anhydride were investigated via gas phase and bulk ultraviolet photoemission spectroscopy and compared to density functional theory calculations. Values for final state effects such as intermolecular polarization were determined and the differing features in the spectra interpreted as a consequence of interactions in the thin films. Additionally, the highest occupied molecular orbitals of the molecules clearly show distinctive peaks originating from vibrational excitations, leading to results for Franck–Condon factors.
The phase diagram of water at negative pressures: Virtual ices
Authors: Conde M. M. , Vega C. , Tribello G. A. , Slater B.
Published: July 2009

The phase diagram of water at negative pressures as obtained from computer simulations for two models of water, TIP4P/2005 and TIP5P is presented. Several solid structures with lower densities than ice Ih, so-called virtual ices, were considered as possible candidates to occupy the negative pressure region of the phase diagram of water. In particular the empty hydrate structures sI, sII, and sH and another, recently proposed, low-density ice structure. The relative stabilities of these structures at 0 K was determined using empirical water potentials and density functional theory calculations. By performing free energy calculations and Gibbs–Duhem integration the phase diagram of TIP4P/2005 was determined at negative pressures. The empty hydrates sII and sH appear to be the stable solid phases of water at negative pressures. The phase boundary between ice Ih and sII clathrate occurs at moderate negative pressures, while at large negative pressures sH becomes the most stable phase. This behavior is in reasonable agreement with what is observed in density functional theory calculations.
Photoluminescence and photoabsorption blueshift of nanostructured ZnO: Skin-depth quantum trapping and electron-phonon coupling
Authors: Li J. W. , Liu X. J. , Yang L. W. , Zhou Z. F. , Xie G. F. , Pan Y. , Wang X. H. , Zhou J. , Li L. T. , Pan Likun , Sun Zhuo , Sun Chang Q.
Published: July 2009

Although the size- and shape-induced blueshift in the photoluminescence and photoabsorption of nanostructured ZnO has been extensively investigated, the underlying mechanism remains yet unclear. Here we show that theoretical reproduction of the observed trends clarifies that the blueshift originates from the Hamiltonian perturbation due to the broken-bond-induced local strain and quantum trapping and electron-phonon coupling in the surface skin up to two atomic layers in depth while bonds in the core interior retain their bulk nature. The extent of the blue shift depends on the tunable fraction of undercoordinated atoms in the surface skin. Therefore, the quantum confinement effect is indeed more “superficial” than first thought [H. Winn, OE Mag. 8, 10 (2005)].
Anisotropic propagation of surface plasmon polaritons caused by oriented molecular overlayer
Authors: Ghazali Fadiah Adlina M. , Fujii Minoru , Hayashi Shinji
Published: July 2009

We performed reverse attenuated total reflection measurements on 50-nm-thick Ag thin films coated with oriented sexithiophene molecular layers. The dispersion curves obtained clearly demonstrate that the wavevectors of surface plasmon polaritons propagating parallel to the molecular orientation have larger magnitudes than those propagating perpendicular to the molecular orientation. The results provide us with an approach to generate anisotropic propagation of surface plasmon polaritons simply controlled by the molecular orientation of an overlayer.
Blueshift in optical band gap in nanocrystalline Zn1−xCaxO films deposited by sol-gel method
Authors: Misra Kamakhya Prakash , Shukla R. K. , Srivastava Atul , Srivastava Anchal
Published: July 2009

A blueshift in the optical band gap of nanocrystalline Zn1−xCaxO thin films has been obtained. A 12.72% enhancement in the band gap of ZnO thin films has been obtained using Ca dopant for the first time. The band gap widens from 3.38 to 3.81 eV as the Ca concentration increases from x=0 to x=0.15. The films are deposited by sol-gel method and have a hexagonal wurtzite phase with no indication of calcium. Grain size lies in the range of 12–92 nm. Atomic force micrographs indicate much smaller rms surface roughness showing significantly smooth surfaces.
Characterization of flow pattern past two spheres in proximity
Authors: Yoon Dong-Hyeog , Yang Kyung-Soo
Published: July 2009

As a follow-up study of flow-induced forces on two nearby spheres [D. Yoon and K. Yang, Phys. Fluids 19, 098103 (2007)], this paper establishes a systematic characterization of flow pattern past two identical spheres in proximity at Re=300. We consider all possible arrangements of two spheres in terms of the distance between the spheres and the angle inclined with respect to the main flow direction. It turns out that significant changes in shedding characteristics are noticed depending on how the two spheres are positioned. Ten distinct flow patterns are identified in total, and a detailed description is given to each pattern. Collecting all the numerical results obtained, we propose two comprehensive tables, one for flow pattern for each arrangement of the spheres and the other for Strouhal number of the corresponding vortex shedding. The perfect geometrical symmetry implied in the flow configuration allows one to use those tables for any two identical spheres arbitrarily positioned in physical space with respect to the main flow direction.
A theoretical study of BeN linear chains: Variational and perturbative approaches
Authors: Pastore Mariachiara , Monari Antonio , Angeli Celestino , Bendazzoli Gian Luigi , Cimiraglia Renzo , Evangelisti Stefano
Published: July 2009

A systematic theoretical study of BeN linear chains by means of both variational (multireference configuration interaction) and perturbative (n-electron valence state perturbation theory) methodologies is reported. Extensive calculations have been performed using atomic natural orbital basis set of increasing size (3s1p, 4s2p1d, and 5s3p2d1f). The problematic task of obtaining a coherent description of the potential energy surface with approximate ab initio methods is addressed. The main difficulty met in the computation of the binding energy of long BeN chains essentially arises from the need of using, as the dissociation is approached, a variational space different from that suitable to treat the system near the equilibrium distance. To overcome this problem, two alternative approaches are presented and the computed dissociation energies are compared to the corresponding full-CI values reported in a recent work [V. Vetere et al., J. Chem. Phys. 130, 024301 (2009)].
Photoluminescence of highly excited AlN: Biexcitons and exciton-exciton scattering
Authors: Leute R. A. R. , Feneberg M. , Sauer R. , Thonke K. , Thapa S. B. , Scholz F. , Taniyasu Y. , Kasu M.
Published: July 2009

Low-temperature photoluminescence spectra of nominally undoped high quality AlN layers on SiC and Al2O3 substrates are reported. Under high excitation conditions, we observe several bands that increase superlinearly with the excitation density. Based on temperature and excitation level dependences recorded on different samples, we identify a band 36 meV below the free A-exciton transition as due to exciton-exciton scattering (P2 band) and a second band down-shifted from the A-exciton transition by 27 meV as due to biexciton recombination. The combined data yield an exciton binding energy of 48 meV.
Si nanopillar array optimization on Si thin films for solar energy harvesting
Authors: Li Junshuai , Yu HongYu , Wong She Mein , Zhang Gang , Sun Xiaowei , Lo Patrick Guo-Qiang , Kwong Dim-Lee
Published: July 2009

In this letter, Si thin film (800 nm thick) with nanopillar array decorated surface is studied via simulation for its solar energy absorption characteristics. It is found that the light absorption is significantly enhanced due to the adding of the Si nanopillar (SiNP) array to the Si thin film. The absorption characteristics of the SiNP structure would be approximately optimum (especially at ∼2.5 eV, the high energy density region in the solar spectrum) when the periodicity of SiNP array is set as ∼500 nm, which can be explained when comparing the incident light wavelength with the periodicity of SiNP array.
Characterization of terahertz field confinement at the end of a tapered metal wire waveguide
Authors: Astley Victoria , Mendis Rajind , Mittleman Daniel M.
Published: July 2009

We present experimental verification of the possibility of strong subwavelength confinement of the terahertz electric field at the end of a tapered metal wire waveguide. The axial field component at the end of the tapered waveguide shows a lateral confinement that is an order of magnitude greater than an untapered waveguide, and over 100 times greater than the free-space wavelength. The axial component is also strongly confined in the propagation direction, in contrast to the radial field component. Comparison to numerical simulation yields excellent agreement when the effect of the detecting probe is included in the analysis.
Phylogeny of Dorippoidea (Crustacea : Decapoda : Brachyura) inferred from three mitochondrial genes
Authors: Sin Y. W. , Lai Joelle C. Y. , Ng Peter K. L. , Chu K. H.
Published: July 2009

The phylogenetic relationships between 10 of 13 genera of crabs from the superfamily Dorippoidea were investigated using mitochondrial 16S rRNA, 12S rRNA and cytochrome c oxidase subunit I gene sequences. The resultant phylogenetic trees based on the three molecular markers support the division of Dorippidae and Ethusidae as monophyletic families within the Dorippoidea. The inferred inter-generic relationships within Dorippidae concur with groupings based on the overall morphology of the carapace and structures of the male first pleopods.
Movement patterns of feral predators in an arid environment – implications for control through poison baiting
Authors: Moseby K. E. , Stott J. , Crisp H.
Published: July 2009

Control of introduced predators is critical to both protection and successful reintroduction of threatened prey species. Efficiency of control is improved if it takes into account habitat use, home range and the activity patterns of the predator. These characteristics were studied in feral cats (Felis catus) and red foxes (Vulpes vulpes) in arid South Australia, and results are used to suggest improvements in control methods. In addition, mortality and movement patterns of cats before and after a poison-baiting event were compared. Thirteen cats and four foxes were successfully fitted with GPS data-logger radio-collars and tracked 4-hourly for several months. High intra-specific variation in cat home-range size was recorded, with 95% minimum convex polygon (MCP) home ranges varying from 0.5 km2 to 132 km2. Cat home-range size was not significantly different from that of foxes, nor was there a significant difference related to sex or age. Cats preferred habitat types that support thicker vegetation cover, including creeklines and sand dunes, whereas foxes preferred sand dunes. Cats used temporary focal points (areas used intensively over short time periods and then vacated) for periods of up to 2 weeks and continually moved throughout their home range. Aerial baiting at a density of 10 baits per km2 was ineffective for cats because similar high mortality rates were recorded for cats in both baited and unbaited areas. Mortality was highest in young male cats. Long-range movements of up to 45 km in 2 days were recorded in male feral cats and movement into the baited zone occurred within 2 days of baiting. Movement patterns of radio-collared animals and inferred bait detection distances were used to suggest optimum baiting densities of ~30 baits per km2 for feral cats and 5 per km2 for foxes. Feral cats exhibited much higher intra-specific variation in activity patterns and home-range size than did foxes, rendering them a potentially difficult species to control by a single method. Control of cats and foxes in arid Australia should target habitats with thick vegetation cover and aerial baiting should ideally occur over areas of several thousand square kilometres because of large home ranges and long-range movements increasing the chance of fast reinvasion. The use of temporary focal points suggested that it may take several days or even weeks for a cat to encounter a fixed trap site within their home range, whereas foxes should encounter them more quickly as they move further each day although they have a similar home-range size. Because of high intra-specific variability in activity patterns and home-range size, control of feral cats in inland Australia may be best achieved through a combination of control techniques.
Antibody status and survival of Australian wild rabbits challenged with rabbit haemorrhagic disease virus
Authors: McPhee S. R. , Butler K. L. , Kovaliski J. , Mutze G. , Capucci L. , Cooke B. D.
Published: July 2009

In Australia, the epidemiology of rabbit haemorrhagic disease virus (RHDV) is complicated by non-pathogenic forms of calicivirus (bCV) co-circulating with RHDV and providing variable protection from RHDV. Currently no bCV virus-specific antibody tests exist; however, a series of four ELISAs used to detect antibodies to RHDV provided an indirect means to detect antibodies to bCV, enabling antibody categories of seronegative, maternal RHDV, RHDV or bCV to be determined. Rabbits (188) from four locations were challenged with RHDV and logistic regression models determined that, for rabbits <15 months old, survival was dependent on antibody titres alone and the relationship did not vary with age, capture site, gender, liveweight or reproductive status. All rabbits survived challenge after reaching 15 months of age, irrespective of their antibody titres. Where bCV antibodies were prevalent in young rabbits, the bCV category did not adequately summarise all information about rabbit survival that can be obtained from antibody titres. Within antibody categories, 95% of rabbits with RHDV, 33% with bCV, 40% with maternal RHDV and 22% with seronegative antibodies survived. The high survival rate of adults implies that natural outbreaks or controlled releases of RHDV will have little impact on adult breeding rabbits. Therefore, where RHDV and bCV are endemic, conventional rabbit-control programs targeting the immune breeding populations should provide the most predictable outcome for long-term maintenance of low rabbit populations.
Estimating the potential for reinvasion by mammalian pests through pest-exclusion fencing
Authors: Connolly Trevor A. , Day Tim D. , King Carolyn M.
Published: July 2009

Pest mammals are completely excluded from Maungatautari Ecological Island, New Zealand, by a 47-km Xcluder pest-proof fence; however, they are commonly sighted directly outside, along the fenceline. Permanent pest exclusion relies on maintaining fence integrity, and enhancing knowledge of pest activity and behaviour at fenced reserves. We describe summer and winter periods of activity and behaviour of mammalian pests directly adjacent to the pest-proof fence. We (1) tested for the effects of adjacent habitat type, breach type and season on the rate of mammalian pest sightings directly at the fence, (2) determined how quickly pest mammals may locate a fence breach, and how likely they are to exploit it, and (3) developed a predictive model to help assess the probability of a pest gaining entry to the sanctuary if repair to a fence breach is delayed. Observations inside the rolled fence hood provided firm evidence that rats travel and forage extensively in this artificial although highly acceptable aboveground habitat, much more than on the ground. We confirm and emphasise that mammalian pests are constantly testing the pest-proof fence. Pests are very common directly outside the fence, and within 24 h there is a very high likelihood that a fence breach will be located and exploited. The greatest threat of reinvasion comes (1) nocturnally, (2) from rodents and (3) in the summer; however, these results also confirm that there is constant risk from multiple pest species, regardless of time of day or season.
Exploratory Techniques for Examining Cluster Dynamics: A Systems Thinking Approach
Authors: Smith Madeline , Brown Ross
Published: July 2009

Economic development agencies worldwide have eagerly embraced clusters as a strategy to boost local economic development. When implementing cluster-based interventions, one of the main issues encountered by many public sector bodies is that the majority of cluster analysis and measurement techniques only give a partial overview of how they actually operate. Often it is the dynamics of collaboration within a cluster that has the biggest influence on overall success. This paper adopts a system thinking approach to help us understand cluster development and inter-firm collaboration. The outcome of this work was the development of a basic five stage conceptual model that helps explain how a cluster develops, together with the changes in company behaviour and company interaction that might be seen at different stages of this developmental trajectory. Using Scotland as an empirical test case, this article highlights the model and examines the problems associated with the adoption of this approach. This methodological approach was shared with other regions working to support clusters to ascertain the relevance of this approach elsewhere. Overall this paper concludes that the model proves to be a useful tool in assessing the varying stages of a cluster's development both within and outside Scotland.
Empowering Glasgow's Tenants through Community Ownership?
Authors: McKee Kim
Published: July 2009

Post 1997, stock transfer has been pivotal to the housing and regeneration agenda of the New Labour government, both at the UK and devolved level. Although a heavily researched policy area, stock transfer research has tended to focus quite narrowly on the perspectives of policymakers, practitioners or members of the transfer association's governing body. To address this research gap and focus more explicitly on the voices of local residents, this paper draws on the case study of the unique two-stage Glasgow housing stock transfer in order to explore ‘community ownership’ and ‘tenant empowerment’ from the perspective of ‘lay’ tenants. Political ambitions for direct democracy and communitarian endeavour have been central to stock transfer agendas in Scotland, where the policy has developed quite distinctly compared with the rest of the UK. Focus group research with tenants in Glasgow, however, highlights that empowerment was not an important priority for tenants at the point of transfer; that the transfer has delivered mixed outcomes in terms of local tenant control; and on the key issue of support for ‘full’ community ownership tenants were unconvinced, and expressed a need for more information.
Spending Time Locally: The Benefit of Time Banks for Local Economies
Authors: Gregory Lee
Published: July 2009

This article explores the potential role of time banks in re-building and sustaining local economies based on two key issues: that time credits need to show that they can help people dependent on limited financial resources; and that they can interact with local businesses. The potential of time credits to interact with local economies has been questioned as alternative community currencies show greater compatibility with business. However, this paper argues that the potential of time credits is substantial. Drawing on recent research with a time bank in the Welsh valleys, this paper explores these two issues, to consider the potential of time banks for local economies, beyond their social intervention status.
Activity of the β-catenin phosphodestruction complex at cell–cell contacts is enhanced by cadherin-based adhesion
Authors: Maher Meghan T. , Flozak Annette S. , Stocker Adam M. , Chenn Anjen , Gottardi Cara J.
Published: July 2009

It is well established that cadherin protein levels impact canonical Wnt signaling through binding and sequestering β-catenin (β-cat) from T-cell factor family transcription factors. Whether changes in intercellular adhesion can affect β-cat signaling and the mechanism through which this occurs has remained unresolved. We show that axin, APC2, GSK-3β and N-terminally phosphorylated forms of β-cat can localize to cell–cell contacts in a complex that is molecularly distinct from the cadherin–catenin adhesive complex. Nonetheless, cadherins can promote the N-terminal phosphorylation of β-cat, and cell–cell adhesion increases the turnover of cytosolic β-cat. Together, these data suggest that cadherin-based cell–cell adhesion limits Wnt signals by promoting the activity of a junction-localized β-cat phosphodestruction complex, which may be relevant to tissue morphogenesis and cell fate decisions during development.
Membrane proteins follow multiple pathways to the basolateral cell surface in polarized epithelial cells
Authors: Farr Glen A. , Hull Michael , Mellman Ira , Caplan Michael J.
Published: July 2009

Newly synthesized apical and basolateral membrane proteins are sorted from one another in polarized epithelial cells. The trans-Golgi network participates in this sorting process, but some basolateral proteins travel from the Golgi to recycling endosomes (REs) before their surface delivery. Using a novel system for pulse–chase microscopy, we have visualized the postsynthetic route pursued by a newly synthesized cohort of Na,K-ATPase. We find that the basolateral delivery of newly synthesized Na,K-ATPase occurs via a pathway distinct from that pursued by the vesicular stomatitis virus G protein (VSV-G). Na,K-ATPase surface delivery occurs at a faster rate than that observed for VSV-G. The Na,K-ATPase does not pass through the RE compartment en route to the plasma membrane, and Na,K-ATPase trafficking is not regulated by the same small GTPases as other basolateral proteins. Finally, Na,K-ATPase and VSV-G travel in separate post-Golgi transport intermediates, demonstrating directly that multiple routes exist for transport from the Golgi to the basolateral membrane in polarized epithelial cells.
Pre–B cell receptor–mediated cell cycle arrest in Philadelphia chromosome–positive acute lymphoblastic leukemia requires IKAROS function
Authors: Trageser Daniel , Iacobucci Ilaria , Nahar Rahul , Duy Cihangir , von Levetzow Gregor , Klemm Lars , Park Eugene , Schuh Wolfgang , Gruber Tanja , Herzog Sebastian , Kim Yong-mi , Hofmann Wolf-Karsten , Li Aihong , Storlazzi Clelia Tiziana , Jäck Hans-Martin , Groffen John , Martinelli Giovanni , Heisterkamp Nora , Jumaa Hassan , Müschen Markus
Published: July 2009

B cell lineage acute lymphoblastic leukemia (ALL) arises in virtually all cases from B cell precursors that are arrested at pre–B cell receptor–dependent stages. The Philadelphia chromosome–positive (Ph+) subtype of ALL accounts for 25–30% of cases of adult ALL, has the most unfavorable clinical outcome among all ALL subtypes and is defined by the oncogenic BCR-ABL1 kinase and deletions of the IKAROS gene in >80% of cases. Here, we demonstrate that the pre–B cell receptor functions as a tumor suppressor upstream of IKAROS through induction of cell cycle arrest in Ph+ ALL cells. Pre–B cell receptor–mediated cell cycle arrest in Ph+ ALL cells critically depends on IKAROS function, and is reversed by coexpression of the dominant-negative IKAROS splice variant IK6. IKAROS also promotes tumor suppression through cooperation with downstream molecules of the pre–B cell receptor signaling pathway, even if expression of the pre–B cell receptor itself is compromised. In this case, IKAROS redirects oncogenic BCR-ABL1 tyrosine kinase signaling from SRC kinase-activation to SLP65, which functions as a critical tumor suppressor downstream of the pre–B cell receptor. These findings provide a rationale for the surprisingly high frequency of IKAROS deletions in Ph+ ALL and identify IKAROS-mediated cell cycle exit as the endpoint of an emerging pathway of pre–B cell receptor–mediated tumor suppression.
An activating mutation in the CSF3R gene induces a hereditary chronic neutrophilia
Authors: Plo Isabelle , Zhang Yanyan , Le Couédic Jean-Pierre , Nakatake Mayuka , Boulet Jean-Michel , Itaya Miki , Smith Steven O. , Debili Najet , Constantinescu Stefan N. , Vainchenker William , Louache Fawzia , de Botton Stéphane
Published: July 2009

We identify an autosomal mutation in the CSF3R gene in a family with a chronic neutrophilia. This T617N mutation energetically favors dimerization of the granulocyte colony-stimulating factor (G-CSF) receptor transmembrane domain, and thus, strongly promotes constitutive activation of the receptor and hypersensitivity to G-CSF for proliferation and differentiation, which ultimately leads to chronic neutrophilia. Mutant hematopoietic stem cells yield a myeloproliferative-like disorder in xenotransplantation and syngenic mouse bone marrow engraftment assays. The survey of 12 affected individuals during three generations indicates that only one patient had a myelodysplastic syndrome. Our data thus indicate that mutations in the CSF3R gene can be responsible for hereditary neutrophilia mimicking a myeloproliferative disorder.
Caleydo: connecting pathways and gene expression
Authors: Streit Marc , Lex Alexander , Kalkusch Michael , Zatloukal Kurt , Schmalstieg Dieter
Published: July 2009

Summary: Understanding the relationships between pathways and the altered expression of their components in disease conditions can be addressed in a visual data analysis process. Caleydo uses novel visualization techniques to support life science experts in their analysis of gene expression data in the context of pathways and functions of individual genes. Pathways and gene expression visualizations are placed in a 3D scene where selected entities (i.e. genes) are visually connected. This allows Caleydo to seamlessly integrate interactive gene expression visualization with cross-database pathway exploration.

Availability: The Caleydo visualization framework is freely available on www.caleydo.org for non-commercial use. It runs on Windows and Linux and requires a 3D capable graphics card.

Contact:  caleydo@icg.tugraz.at; streit@icg.tugraz.at

Supplementary information:  Supplementary data are available at Bioinformatics online.
An optimization model for metabolic pathways
Authors: Planes F. J. , Beasley J. E.
Published: July 2009

Motivation: Different mathematical methods have emerged in the post-genomic era to determine metabolic pathways. These methods can be divided into stoichiometric methods and path finding methods. In this paper we detail a novel optimization model, based upon integer linear programming, to determine metabolic pathways. Our model links reaction stoichiometry with path finding in a single approach. We test the ability of our model to determine 40 annotated Escherichia coli metabolic pathways. We show that our model is able to determine 36 of these 40 pathways in a computationally effective manner.

Contact:  john.beasley@brunel.ac.uk

Supplementary information:  Supplementary data are available at Bioinformatics online.
Adenovirus vector‐mediated upregulation of spermidine /spermine N1‐acetyltransferase impairs human gastric cancer growth in vitro and in vivo
Authors: Liu Bin , Sun Hui , Wang Wei , Li Wei , Yan Yun‐Fei , Chen Shi‐Min , Yang Ya‐Pei , Xu Chun‐Xiao , Xin Jia‐Xuan , Liu Xian‐Xi
Published: July 2009

Spermidine/spermine N1‐acetyltransferase (SSAT) is the rate‐limiting step in polyamine catabolism. In a previous study, we constructed a recombinant adenovirus, Ad‐SSAT, which can express human SSAT. In the present study, we investigated the effect of upregulated and downregulated SSAT on gastric cancer cells. We found that upregulated SSAT could inhibit the growth of MGC803 and SGC7901 cells, whereas adverse results were found with downregulated SSAT. We further analyzed cell cycle profiles and the expression levels of the major cell cycle regulatory proteins of S phase. The results showed that the growth inhibition was caused by S phase arrest. Ad‐SSAT suppressed the expression of cyclin A and nuclear factor E2F1 in MGC803 and SGC7901 cells. We observed the E2F promoter activity caused by Ad‐SSAT using a reporter gene assay. We also investigated the antitumorigenicity of upregulated SSAT by Ad‐SSAT using a SGC7901 xenograft model in nude mice. Our results suggest that the upregulation of SSAT by Ad‐SSAT infection inhibited the growth of gastric cancer in vitro and in vivo. Ad‐SSAT arrested gastric cancer cells in S phase, which was mediated through downregulation of the cyclin A‐E2F signaling pathway. (Cancer Sci 2009); 000: 000–000
Inhibition of the active principle of the weak opioid tilidine by the triazole antifungal voriconazole
Authors: Grün Barbara , Krautter Stefanie , Riedel Klaus‐Dieter , Mikus Gerd
Published: July 2009

WHAT IS ALREADY KNOWN ABOUT THE SUBJECT

• Tilidine, a World Health Organization level II analgesic, is a high extraction drug subject to pronounced first‐pass metabolism, resulting in a low absolute bioavailability.

• The analgesic activity of tilidine is almost exclusively exerted through its metabolite nortilidine, which easily penetrates the blood–brain barrier and binds to the µ‐opioid receptor as a potent agonist.

• In vitro, tilidine has been shown to be metabolized to nortilidine by N‐demethylation via CYP3A4 and CYP2C19; furthermore, strong CYP3A4 and CYP2C19 inhibitors inhibited the formation of nortilidine, suggesting that these inhibitors will lead to a reduction of tilidine efficiency in vivo.

WHAT THIS PAPER ADDS

• Co‐administration of tilidine and the potent CYP3A4 and CYP2C19 inhibitor voriconazole resulted in a major pharmacokinetic interaction that was partly associated with changes in the analgesic effect.

• Voriconazole inhibits both metabolic steps in the sequential metabolism of tilidine resulting in an increased exposure of the active nortilidine.

• The incidence of adverse reactions was also significantly increased.

AIMS

To investigate in vivo the influence of the potent CYP2C19 and CYP3A4 inhibitor voriconazole on the pharmacokinetics and analgesic effects of tilidine.

METHODS

Sixteen healthy volunteers received voriconazole (400 mg) or placebo together with a single oral dose of tilidine (100 mg). Blood samples and urine were collected for 24 h and experimental pain was determined by using the cold pressor test. Noncompartimental analysis was performed to determine pharmacokinetic parameters of tilidine, nortilidine and voriconazole, whereas pharmacodynamic parameters were analysed by nonparametric repeated measures anova (Friedman).

RESULTS

Voriconazole caused a 20‐fold increase in exposition of tilidine in serum [AUC 1250.8 h*ng ml−1, 95% confidence interval (CI) 1076.8, 1424.9 vs. 61 h*ng ml−1, 95% CI 42.6, 80.9; P < 0.0001], whereas the AUC of nortilidine also increased 2.5‐fold. After voriconazole much lower serum concentrations of bisnortilidine were observed. The onset of analgesic activity occurred later with voriconazole, which is in agreement with the prolonged tmax of nortilidine (0.78 h, 95% CI 0.63, 0.93 vs. 2.5 h, 95% CI 1.85, 3.18; P < 0.0001) due to the additional inhibition of nortilidine metabolism to bisnortilidine. After voriconazole the AUC under the pain withdrawal–time curve was reduced compared with placebo (149 s h−1, 95% CI 112, 185 vs. 175 s h−1, 95% CI 138, 213; P < 0.016), mainly due to the shorter withdrawal time 0.75 h after tilidine administration.

CONCLUSIONS

Voriconazole significantly inhibited the sequential metabolism of tilidine with increased exposure of the active nortilidine. Furthermore, the incidence of adverse events was almost doubled after voriconazole and tilidine.