bluuebunny/crossref_metadata_2025 huggingface dataset:
Giant liposome spreading on a silicon wall
Authors: Zhang Ying , Chen Yan , Fan Hui
Published: August 2011

The spreading of a giant liposome on a vertical silicon wall can be realized when the gravity effect on the spreading is negligible. The dynamic spreading process is experimentally observed and recorded, while the evolution of the liposome shape and the change of the contact angle are quantitatively examined. Based on this, the spreading process, especially the contact line of the liposome on the silicon wall, is modeled by a non-equilibrium thermodynamics formulation. The driving force of the spreading process is the combination of the surface/interfacial tensions, and the mobility of the contact line determines the speed of spreading. The experimental data of liposome dimensions during the dynamic spreading process are closely fitted by the proposed model.
Simultaneous measurement of thermal diffusivity and optical absorption coefficient using photothermal radiometry. II Multilayered solids
Authors: Salazar Agustín , Fuente Raquel , Apiñaniz Estibaliz , Mendioroz Arantza , Celorrio R.
Published: August 2011

The aim of this work is to analyze the ability of modulated photothermal radiometry to retrieve the thermal diffusivity and the optical absorption coefficient of layered materials simultaneously. First, we extend the thermal quadrupole method to calculate the surface temperature of semitransparent multilayered materials. Then, this matrix method is used to evaluate the influence of heat losses by convection and radiation, the influence of the use of thin paint layers on the accuracy of thermal diffusivity measurements, and the effect of lateral heat diffusion due to the use of Gaussian laser beams. Finally, we apply the quadrupole method to retrieve (a) the thermal contact resistance in glass stacks and (b) the thermal diffusivity and optical absorption coefficient depth profiles in heterogeneous materials with continuously varying physical properties, as is the case of functionally graded materials and partially cured dental resins.
Optical touch screen based on waveguide sensing
Authors: Pedersen Henrik C. , Jakobsen Michael L. , Hanson Steen G. , Mosgaard Morten , Iversen Theis , Korsgaard Jorgen
Published: August 2011

We disclose a simple, optical touch screen technique based on a planar injection molded polymer waveguide, a single laser, and a small linear detector array. The solution significantly reduces the complexity and cost as compared to existing optical touch technologies. Force detection of a touching finger is also demonstrated.
Low voltage fabrication of sub-nanometer insulating layers on hydrogenated diamond
Authors: Wang Tao , Boer-Duchemin Elizabeth , Tranvouez Edern , Cartwright Richard , Comtet Geneviève , Dujardin Gérald , Mayne Andrew J.
Published: August 2011

A new regime of electrochemical anodic oxidation with an atomic force microscope (AFM) is introduced for producing insulating layers on a hydrogenated diamond surface. In this new regime, when a low surface voltage (VS<+2 V) is applied to the sample, an insulating layer is created without any measurable change in the topography. Insulating layers created in this fashion are shown to preserve the high sub-surface conductance of hydrogenated diamond surfaces, contrary to the oxide layers accompanied by a topographic change, which destroy sub-surface conductance.
Structure of Sn1−xGex random alloys as obtained from the coherent potential approximation
Authors: Pulikkotil J. J. , Chroneos A. , Schwingenschlögl U.
Published: August 2011

The structure of the Sn1−xGex random alloys is studied using density functional theory and the coherent potential approximation. We report on the deviation of the Sn1−xGex alloys from Vegard’s law, addressing their full compositional range. The findings are compared to the related Si1−xGex alloys and to experimental results. Interestingly, the deviation from Vegard’s law is quantitatively and qualitatively different between the Sn1−xGex and Si1−xGex alloys. An almost linear dependence of the bulk modulus as a function of composition is found for Si1−xGex, whereas for Sn1−xGex the dependence is strongly nonlinear.
Calculations show improved photoelectrochemical performance for N, Ce, and Ce + N doped anatase TiO2
Authors: Zhang Yun Geng , Wang Yuan Xu
Published: August 2011

The effect of substitutional N, Ce, and Ce + N doping on the electronic structure and optical properties of anatase TiO2 have been investigated by using first-principles calculations and considering the strong correlation effect. It is found that Ce + N doping results in bandgap narrowing and also leads to a red-shift of the absorption edge of TiO2, which could meet the demand for water splitting. The decreases in the bandgap are 0.47 eV, 0.21 eV, and 1.05 eV by N, Ce, and Ce + N doping, respectively. Magnetism appears in N and Ce + N doped TiO2, which is attributed to the mismatch between the spin up and spin down states of O-2p, N-2p, and Ce-4f (for Ce + N doped). We predict that Ce + N doping is one of the best choices for enhancing the photoelectrochemical activity of TiO2.
Transistor laser with simultaneous electrical and optical output at 20 and 40 Gb/s data rate modulation
Authors: Tan F. , Bambery R. , Feng M. , Holonyak, N.
Published: August 2011

A single quantum well transistor laser (cavity length L = 300 μm) has been designed and fabricated that operates with threshold ITH = 18 mA at 15 °C and 14 mA at 0 °C. Due to the “fast” base recombination lifetime (τB < 29 ps), the transistor laser demonstrates reduced photon-carrier resonance amplitude (<4 dB) over its entire bias range and a modulation bandwidth f-3dB = 9.8 GHz at 15 °C for IB/ITH = 3.3 and 17 GHz at 0 °C for IB/ITH = 6.4. Under the same bias conditions, simultaneous electrical and optical “open-eye” signal operations are demonstrated at 20 and 40 Gb/s data rate modulation.
Polarity selective etching: A self-assisted route for fabricating high density of c-axis oriented tapered GaN nanopillars
Authors: Ghosh A. , Bhasker H. P. , Mukherjee A. , Kundu T. , Singh B. P. , Dhar S. , De S. , Chowdhury A.
Published: August 2011

High density of c-axis oriented tapered GaN nanopillars are fabricated simply by exposing GaN epitaxial layers in argon–chlorine plasma without any prior lithographic processing. The nature and the formation process of the pillars are investigated by different optical and structural characterization techniques. Our study reveals that the pillars are columnar inversion domains with distinctly different optical properties as compared to the bulk. These are formed as a result of a polarity selective etching process.
Fabrication, electrical characterization, and modeling of fully-porous pn junctions
Authors: Bacci N. , Diligenti A. , Barillaro G.
Published: August 2011

In this work, fabrication, electrical characterization, and modeling of fully porous pn junctions (FPJs) consisting of elemental mesoscopic crystalline junctions operating in parallel, is presented. FPJs are fabricated by anodic etching of a pn crystalline substrate and show a rectifying behavior strongly dependent on PS surface termination, as proved by electrical measurements performed after both room-temperature aging and thermal-oxidation treatment. Modeling of FPJs is performed using a lumped equivalent circuit consisting of a diode, taking into account the elemental mesoscopic junctions, and two resistances acting one in series and one in parallel to the diode, the latter taking into account conduction paths at the silicon mesocrystal surface. Best fitting of experimental data results in good agreement between theoretical and measured I-V curves, thus corroborating the proposed model.
Temperature-dependent photoresponse characteristics of CuAlSe2 layers by photocurrent spectroscopy
Authors: Lee S. Y. , Hong K. J. , Jeong T. S. , Youn C. J.
Published: August 2011

Temperature-dependent photoresponse variation on the CuAlSe2 layers was investigated by photocurrent (PC) spectroscopy as a function of temperature. Three peaks of A, B, and C caused by the band-to-band transition were observed. From these PC peaks, the temperature-dependent band-gap energy was well described by Eg(T) = 2.8382 − (8.68 × 10−4)T2/(155 + T). Thus, the parameter of the split valence band on CuAlSe2 was directly extracted out by means of the PC spectroscopy. The crystal field splitting and the spin-orbit splitting were estimated to be 0.1641 and 0.1778 eV at 10 K, respectively. However, the PC intensities decreased with decreasing temperature. It is against our expectation that the PC intensities increase with decreasing temperature. From the relation of log Jph versus 1/T, where Jph is the PC density, two dominant levels were observed, one at high temperatures and the other at low temperatures. We found out that the activation energy of 48.8 meV at high temperatures is related to the binding energy of the free exciton, whereas the PC-intensity variation at a low temperature below 100 K remains constant. This suggests that trapping centers due to native defects and impurities in CuAlSe2 limit the photoresponse with decreasing temperature.
The electronic structure origin for ultrahigh glass-forming ability of the FeCoCrMoCBY alloy system
Authors: Lu Yunzhuo , Huang Yongjiang , Shen Jun
Published: August 2011

The authors report the effect of the addition of cobalt on glass-forming ability (GFA) in Fe-Co-Cr-Mo-C-B-Y bulk metallic glasses using Raman scattering and x-ray photoelectron spectroscopy. Among the alloy system, the alloy with 7% Co displays a unique electronic structure including the minimum core-level binding energy and the maximum Raman peak frequency. The origin of the superhigh GFA for the 7% Co alloy is discussed in terms of its unique electronic structure that leads to the densest atomic packing and strongest directional bonds.
Polycyclic aromatic hydrocarbon-isomer fragmentation pathways: Case study for pyrene and fluoranthene molecules and clusters
Authors: Seitz F. , Holm A. I. S. , Zettergren H. , Johansson H. A. B. , Rosén S. , Schmidt H. T. , Ławicki A. , Rangama J. , Rousseau P. , Capron M. , Maisonny R. , Domaracka A. , Adoui L. , Méry A. , Manil B. , Huber B. A. , Cederquist H.
Published: August 2011

We report on measurements of the ionization and fragmentation of polycyclic aromatic hydrocarbon (PAH) targets in Xe20 + + C16H10 and Xe20 + + [C16H10]k collisions and compare results for the two C16H10 isomers: pyrene and fluoranthene. For both types of targets, i.e., for single PAH molecules isolated in vacuum or for isomerically pure clusters of one of the molecules, the resulting fragment spectra are surprisingly similar. However, we do observe weak but significant isomer effects. Although these are manifested in very different ways for the monomer and cluster targets, they both have at their roots small differences (<2.5 eV) between the total binding energies of neutral, and singly and multiply charged pyrene and fluoranthene monomers. The results will be discussed in view of the density functional theory calculations of ionization and dissociation energies for fluoranthene and pyrene. A simple classical over-the-barrier model is used to estimate cross sections for single- and multiple-electron transfer between PAHs and ions. Calculated single and multiple ionization energies, and the corresponding model PAH ionization cross sections, are given.
Dust accumulation effect on efficiency of Si photovoltaic modules
Authors: Cabanillas R. E. , Munguía H.
Published: August 2011

We experimentally studied the electrical efficiency effects of naturally forming atmospheric dust deposits on commercial photovoltaic panels. The variable considered for measurements was the electric potential for three commercial silicon modules: monocrystalline, polycrystalline, and amorphous. A mathematical model was developed to determine maximum potential as a function of temperature and of total incident radiation. The study presents two essential parts: the naturally deposited dust particles and the variation in maximum electric potential between clean and dirty modules. The results indicate that the maximum reduction in potential is around of 6% for monocrystalline and polycrystalline modules and of 12% for the amorphous silicon.
Instability of magnetohydrodynamic flow in an annular channel at high Hartmann number
Authors: Zhao Yurong , Zikanov Oleg , Krasnov Dmitry
Published: August 2011

Instability of a flow of an electrically conducting fluid in an annular channel is analyzed. Strong constant magnetic field is imposed in the axial direction. Similarly to toroidal duct experiments, the flow is driven by the azimuthal Lorentz force resulting from the interaction between the magnetic field and the radial electric currents created by a difference of electric potential imposed between the cylinders. The instability of the base flow, while clearly of centrifugal nature, is significantly different from the Dean instability detected earlier in hydrodynamic systems and similar MHD systems at low and moderate magnetic fields. Growing perturbations are oscillating and axisymmetric and consist of counter-rotating toroidal vortices arranged side by side in the radial direction and having meridional cross-sections in the form of elongated ellipses oriented slightly obliquely to the axial direction. Simulations of the secondary flow show an interesting feature of periodic transitions between two symmetric solutions.
Temperature dependence dynamical permeability characterization of magnetic thin film using near-field microwave microscopy
Authors: Hung Le Thanh , Phuoc Nguyen N. , Wang Xuan-Cong , Ong C. K.
Published: August 2011

A temperature dependence characterization system of microwave permeability of magnetic thin film up to 5 GHz in the temperature range from room temperature up to 423 K is designed and fabricated as a prototype measurement fixture. It is based on the near field microwave microscopy technique (NFMM). The scaling coefficient of the fixture can be determined by (i) calibrating the NFMM with a standard sample whose permeability is known; (ii) by calibrating the NFMM with an established dynamic permeability measurement technique such as shorted microstrip transmission line perturbation method; (iii) adjusting the real part of the complex permeability at low frequency to fit the value of initial permeability. The algorithms for calculating the complex permeability of magnetic thin films are analyzed. A 100 nm thick FeTaN thin film deposited on Si substrate by sputtering method is characterized using the fixture. The room temperature permeability results of the FeTaN film agree well with results obtained from the established short-circuited microstrip perturbation method. Temperature dependence permeability results fit well with the Landau–Lifshitz–Gilbert equation. The temperature dependence of the static magnetic anisotropy $H_K^{{\rm sta}}$HK sta , the dynamic magnetic anisotropy $H_K^{{\rm dyn}}$HK dyn , the rotational anisotropy Hrot, together with the effective damping coefficient αeff, ferromagnetic resonance fFMR, and frequency linewidth Δf of the thin film are investigated. These temperature dependent magnetic properties of the magnetic thin film are important to the high frequency applications of magnetic devices at high temperatures.
Adsorption of monovalent and divalent cations on planar water-silica interfaces studied by optical reflectivity and Monte Carlo simulations
Authors: Porus Maria , Labbez Christophe , Maroni Plinio , Borkovec Michal
Published: August 2011

Adsorption on planar silica substrates of various monovalent and divalent cations from aqueous solution is studied by optical reflectivity. The adsorbed amount is extracted by means of a thin slab model. The experimental data are compared with grand canonical Monte Carlo titration simulations at the primitive model level. The surface excess of charge due to adsorbed cations is found to increase with pH and salt concentration as a result of the progressive dissociation of silanol groups. The simulations predict, in agreement with experiments, that the surface excess of charge from divalent ions is much larger than from monovalent ions. Ion-ion correlations explain quantitatively the enhancement of surface ionization by multivalent cations. On the other hand, the combination of experimental and simulation results strongly suggests the existence of a second ionizable site in the acidic region. Variation of the distance of closest approach between the ions and surface sites captures ion specificity of water-silica interfaces in an approximate fashion.
The effect of interstitial fluid viscosity on particle segregation in a slurry rotating drum
Authors: Chou S. H. , Liao C. C. , Hsiau S. S.
Published: August 2011

Although the segregation of dry granular surface flow has been widely studied, cases where the air is completely replaced by a liquid still remain unexplored. In this study, we report on experiments performed to investigate the phenomena of particle segregation and flowing behavior in a rotating drum with liquids of different viscosities and different filling degrees. The experimental results indicate that the viscosity of the interstitial fluid has a significant effect on the granular flow in the slurry granular flow. The segregation index and angle of repose are shown to decrease with increased liquid viscosity. When the liquid viscosity is the same, the increase in filling degree causes the segregation index to increase, while the net rate of mixing seems to decrease. A new dimensionless flow variable is used to distinguish the flow regimes. We find that the flow regime changes from rolling regime to cascading regime when the dimensionless flow variable is below a critical value. Furthermore, the change of segregation index occurs during the transition of the granular flow regime.
The effect of surface shear viscosity on the damping of oscillations in millimetric liquid bridges
Authors: Herrada Miguel A. , Montanero José M. , Vega José M.
Published: August 2011

The damping rate of the small free oscillations in a non-cylindrical, axi-symmetric liquid bridge between two circular disks is calculated and compared with some previous experimental measurements using hexadecane in a millimetric liquid bridge. Current theories, accounting for viscous damping in both the boundary layers attached to the disks and the bulk, underestimated the measured damping by a O(1) quantity; and no improvement resulted from calculations based on the full Navier-Stokes equations. These discrepancies are essentially eliminated in this paper considering the effect of the surface shear viscosity (whose value results from empirical fitness), which could be due to the presence of a contaminating monolayer. Some consequences are extracted in connection with surface wave damping in micro-fluidic devices.
Reverse nonequilibrium molecular dynamics simulation of thermal conductivity in nanoconfined polyamide-6,6
Authors: Eslami Hossein , Mohammadzadeh Laila , Mehdipour Nargess
Published: August 2011

A new molecular dynamics simulation method, with coupling to external baths, is used to perform equilibrium simulations on polyamide-6,6 trimers nanoconfined between graphene surfaces, in equilibrium with the bulk polymer. The method is coupled with the reverse nonequilibrium molecular dynamics simulation technique to exchange heat in the direction normal to the surfaces. To be able to study the effect of confinement on the heat conductance in nanoconfined pores, in this work a number of simulations on systems with different pore sizes are done. It is concluded that the coefficient of heat conductivity depends on the degree of polymer layering between the surfaces and on the pore width. Our results further indicate a considerable temperature drop at the interface between the surfaces and polymer. The calculated Kapitza lengths depend on the intersurface distance and on the layering of the polymer nanoconfined between the surfaces.
One-dimensional model of the programming kinetics of conductive-bridge memory cells
Authors: Jameson John R. , Gilbert Nad , Koushan Foroozan , Saenz Juan , Wang Janet , Hollmer Shane , Kozicki Michael N.
Published: August 2011

A one-dimensional model of filament growth in conductive-bridge memory cells is presented, in which ions are thermally excited from the anode surface into the electrolyte, pulled by the electric field through a periodic series of wells and reduced at the cathode to form a metallic filament. The voltage, temperature, and thickness dependencies of the time required to program a cell are calculated, and material parameters for Ag/GeS2/W cells are obtained by comparison to experiment. The relation of the model to recent observations of quantized conductance is highlighted, as is the need for further study of the Ag/GeS2 interface.
First-principles prediction of a two dimensional electron gas at the BiFeO3/SrTiO3 interface
Authors: Zhang Zhen , Wu Ping , Chen Lang , Wang Junling
Published: August 2011

The structural and electronic properties of the BiFeO3(BFO)/SrTiO3(STO) heterostructure are studied using supercell approach by ab-initio density functional theory calculations. Our calculations indicate that a two-dimensional electron gas (2DEG) exists at the n-type (BiO)+ and (TiO2)0 interface, due to the fact that electronic reconstruction is expected to avoid the polar catastrophe. Moreover, the large polarization discontinuity between the paraelectric SrTiO3 and ferroelectric BiFeO3 brings about distinguishable 2DEG behaviors to the n-type BiO/TiO2 interfaces, due to the asymmetric screening charge.
Conduction mechanism of TiN/HfOx/Pt resistive switching memory: A trap-assisted-tunneling model
Authors: Yu Shimeng , Guan Ximeng , Wong H.-S. Philip
Published: August 2011

The conduction mechanism of metal oxide resistive switching memory is debated in the literature. We measured the I-V characteristics below the switching voltages through TiN/HfOx/Pt memory stack and found the conduction cannot be described by the commonly used Poole-Frenkel model, because the fitted dielectric constant and the trap energy are unreasonable as compared to their known values. Therefore, we provide an alternate viewpoint based on a trap-assisted-tunneling model. Agreement of the bias polarity/temperature/resistance state-dependent conduction behavior was achieved between this model and experimental data. And insights for the multilevel capability due to the control of tunneling distance were obtained.
Time-domain terahertz spectroscopy of spin state transition in [Fe(NH2 − trz)3]2+ spin crossover compounds
Authors: Viquerat B. , Degert J. , Tondusson M. , Freysz E. , Mauriac C. , Létard J. F.
Published: August 2011

We have measured the evolution of the THz spectrum of iron(II) spin crossover compounds within the low-spin/high-spin thermal hysteresis loop in the 0.6–6 THz frequency range. This study enabled to follow both the variations of the refractive optical index and absorption during the spin state transition. Marked absorptions centered ∼2 – 3 THz and ∼5 THz shifting with the spin state are revealed. Our work provides a means to store optically information and to read it out in the THz domain and also offers indications about the structural evolution occurring during the spin state transition.
Optical properties of high quality Cu2ZnSnSe4 thin films
Authors: Luckert F. , Hamilton D. I. , Yakushev M. V. , Beattie N. S. , Zoppi G. , Moynihan M. , Forbes I. , Karotki A. V. , Mudryi A. V. , Grossberg M. , Krustok J. , Martin R. W.
Published: August 2011

Cu2ZnSnSe4 thin films, fabricated on bare or molybdenum coated glass substrates by magnetron sputtering and selenisation, were studied by a range of techniques. Photoluminescence spectra reveal an excitonic peak and two phonon replicas of a donor-acceptor pair (DAP) recombination. Its acceptor and donor ionisation energies are 27 and 7 meV, respectively. This demonstrates that high-quality Cu2ZnSnSe4 thin films can be fabricated. An experimental value for the longitudinal optical phonon energy of 28 meV was estimated. The band gap energy of 1.01 eV at room temperature was determined using optical absorption spectra.
Electric control of magnon frequencies and magnetic moment of bismuth ferrite thin films at room temperature
Authors: Kumar Ashok , Scott J. F. , Katiyar R. S.
Published: August 2011

Here, we report the tuning of room-temperature magnon frequencies from 473 GHz to 402 GHz (14%) and magnetic moment from 4 to 18 emu/cm3 at 100 Oe under the application of external electric fields (E) across interdigital electrodes in BiFeO3 (BFO) thin films. A decrease in magnon frequencies and increase in phonon frequencies were observed with Magnon and phonon Raman intensities are asymmetric with polarity, decreasing with positive E (+E) and increasing with negative E (−E) where polarity is with respect to in-plane polarization P. The magnetoelectric coupling (α) is proved to be linear and a rather isotropic α = 8.5 × 10−12 sm−1.
Exciton-plasmon-photon conversion in silver nanowire: Polarization dependence
Authors: Wang Lu-Lu , Zou Chang-Ling , Ren Xi-Feng , Liu Ai-Ping , Lv Liu , Cai Yong-Jing , Sun Fang-Wen , Guo Guang-Can , Guo Guo-Ping
Published: August 2011

Polarization dependence of the exciton-plasmon-photon conversion in silver nanowire-quantum dots structure was investigated using a scanning confocal microscope system. We found that the fluorescence enhancement of the CdSe nanocrystals was correlated with the angle between the excitation light polarization and the silver nanowire direction. The polarization of the emission was also related with the nanowire direction. It was in majority in the direction parallel with nanowire due to the nano-antenna effect.
Multiple new site-specific recombinases for use in manipulating animal genomes
Authors: Nern Aljoscha , Pfeiffer Barret D. , Svoboda Karel , Rubin Gerald M.
Published: August 2011

Site-specific recombinases have been used for two decades to manipulate the structure of animal genomes in highly predictable ways and have become major research tools. However, the small number of recombinases demonstrated to have distinct specificities, low toxicity, and sufficient activity to drive reactions to completion in animals has been a limitation. In this report we show that four recombinases derived from yeast—KD, B2, B3, and R—are highly active and nontoxic in
Drosophila
and that KD, B2, B3, and the widely used FLP recombinase have distinct target specificities. We also show that the KD and B3 recombinases are active in mice.
Legume-Nodulating Betaproteobacteria: Diversity, Host Range, and Future Prospects
Authors: Gyaneshwar Prasad , Hirsch Ann M. , Moulin Lionel , Chen Wen-Ming , Elliott Geoffrey N. , Bontemps Cyril , Estrada-de los Santos Paulina , Gross Eduardo , dos Reis Fabio Bueno , Sprent Janet I. , Young J. Peter W. , James Euan K.
Published: August 2011

Rhizobia form specialized nodules on the roots of legumes (family Fabaceae) and fix nitrogen in exchange for carbon from the host plant. Although the majority of legumes form symbioses with members of genus Rhizobium and its relatives in class Alphaproteobacteria, some legumes, such as those in the large genus Mimosa, are nodulated predominantly by betaproteobacteria in the genera Burkholderia and Cupriavidus. The principal centers of diversity of these bacteria are in central Brazil and South Africa. Molecular phylogenetic studies have shown that betaproteobacteria have existed as legume symbionts for approximately 50 million years, and that, although they have a common origin, the symbiosis genes in both subclasses have evolved separately since then. Additionally, some species of genus Burkholderia, such as B. phymatum, are highly promiscuous, effectively nodulating several important legumes, including common bean (Phaseolus vulgaris). In contrast to genus Burkholderia, only one species of genus Cupriavidus (C. taiwanensis) has so far been shown to nodulate legumes. The recent availability of the genome sequences of C. taiwanensis, B. phymatum, and B. tuberum has paved the way for a more detailed analysis of the evolutionary and mechanistic differences between nodulating strains of alpha- and betaproteobacteria. Initial analyses of genome sequences have suggested that plant-associated Burkholderia spp. have lower G+C contents than Burkholderia spp. that are opportunistic human pathogens, thus supporting previous suggestions that the plant- and human-associated groups of Burkholderia actually belong in separate genera.
Learning and discrimination of cuticular hydrocarbons in a social insect
Authors: van Wilgenburg Ellen , Felden Antoine , Choe Dong-Hwan , Sulc Robert , Luo Jun , Shea Kenneth J. , Elgar Mark A. , Tsutsui Neil D.
Published: August 2011

Social insect cuticular hydrocarbon (CHC) mixtures are among the most complex chemical cues known and are important in nest-mate, caste and species recognition. Despite our growing knowledge of the nature of these cues, we have very little insight into how social insects actually perceive and discriminate among these chemicals. In this study, we use the newly developed technique of differential olfactory conditioning to pure, custom-designed synthetic colony odours to analyse signal discrimination in Argentine ants,
Linepithema humile
. Our results show that tri-methyl alkanes are more easily learned than single-methyl or straight-chain alkanes. In addition, we reveal that Argentine ants can discriminate between hydrocarbons with different branching patterns and the same chain length, but not always between hydrocarbons with the same branching patterns but different chain length. Our data thus show that biochemical characteristics influence those compounds that ants can discriminate between, and which thus potentially play a role in chemical signalling and nest-mate recognition.
Neuronal growth cones respond to laser-induced axonal damage
Authors: Wu Tao , Mohanty Samarendra , Gomez-Godinez Veronica , Shi Linda Z. , Liaw Lih-Huei , Miotke Jill , Meyer Ronald L. , Berns Michael W.
Published: August 2011

Although it is well known that damage to neurons results in release of substances that inhibit axonal growth, release of chemical signals from damaged axons that attract axon growth cones has not been observed. In this study, a 532 nm 12 ns laser was focused to a diffraction-limited spot to produce site-specific damage to single goldfish axons
in vitro
. The axons underwent a localized decrease in thickness (‘thinning’) within seconds. Analysis by fluorescence and transmission electron microscopy indicated that there was no gross rupture of the cell membrane. Mitochondrial transport along the axonal cytoskeleton immediately stopped at the damage site, but recovered over several minutes. Within seconds of damage nearby growth cones extended filopodia towards the injury and were often observed to contact the damaged site. Turning of the growth cone towards the injured axon also was observed. Repair of the laser-induced damage was evidenced by recovery of the axon thickness as well as restoration of mitochondrial movement. We describe a new process of growth cone response to damaged axons. This has been possible through the interface of optics (laser subcellular surgery), fluorescence and electron microscopy, and a goldfish retinal ganglion cell culture model.
Methods to infer transmission risk factors in complex outbreak data
Authors: Cauchemez Simon , Ferguson Neil M.
Published: August 2011

Data collected during outbreaks are essential to better understand infectious disease transmission and design effective control strategies. But analysis of such data is challenging owing to the dependency between observations that is typically observed in an outbreak and to missing data. In this paper, we discuss strategies to tackle some of the ongoing challenges in the analysis of outbreak data. We present a relatively generic statistical model for the estimation of transmission risk factors, and discuss algorithms to estimate its parameters for different levels of missing data. We look at the problem of computational times for relatively large datasets and show how they can be reduced by appropriate use of discretization, sufficient statistics and some simple assumptions on the natural history of the disease. We also discuss approaches to integrate parametric model fitting and tree reconstruction methods in coherent statistical analyses. The methods are tested on both real and simulated datasets of large outbreaks in structured populations.
Challenges of ecological monitoring: estimating population abundance from sparse trap counts
Authors: Petrovskaya Natalia , Petrovskii Sergei , Murchie Archie K.
Published: August 2011

Ecological monitoring aims to provide estimates of pest species abundance—this information being then used for making decisions about means of control. For invertebrate species, population size estimates are often based on trap counts which provide the value of the population density at the traps' location. However, the use of traps in large numbers is problematic as it is costly and may also be disruptive to agricultural procedures. Therefore, the challenge is to obtain a reliable population size estimate from sparse spatial data. The approach we develop in this paper is based on the ideas of numerical integration on a coarse grid. We investigate several methods of numerical integration in order to understand how badly the lack of spatial data can affect the accuracy of results. We first test our approach on simulation data mimicking spatial population distributions of different complexity. We show that, rather counterintuitively, a robust estimate of the population size can be obtained from just a few traps, even when the population distribution has a highly complicated spatial structure. We obtain an estimate of the minimum number of traps required to calculate the population size with good accuracy. We then apply our approach to field data to confirm that the number of trap/sampling locations can be much fewer than has been used in many monitoring programmes. We also show that the accuracy of our approach is greater that that of the statistical method commonly used in field studies. Finally, we discuss the implications of our findings for ecological monitoring practice and show that the use of trap numbers ‘smaller than minimum’ may still be possible but it would result in a paradigm shift: the population size estimates should be treated probabilistically and the arising uncertainty may introduce additional risk in decision-making.
The time-dependent development of electric double-layers in pure water at metal electrodes: the effect of an applied voltage on the local pH
Authors: Morrow R. , McKenzie D. R.
Published: August 2011

Water maintains a pH value of 7 owing to a balance between dissociation into hydronium (H
3
O
+
) and hydroxide (OH
−
) ions and their recombination. An examination is made of the effect of applying voltages from 0.1 to 0.82 V on these ions between metal electrodes which act as blocking electrodes. The movement of hydronium ions away from and hydroxide ions towards the anode is followed. This movement results in the formation of an ion double-layer with a steeply rising electric field and a maximum pH of approximately 12. At the cathode, the opposite occurs and the pH reaches a minimum of approximately 1.7. The time constant for double-layer formation is found to increase exponentially with voltage, and the pH at each electrode varies linearly with voltage; thus, the pH can be controlled systematically at each electrode. The dimensions of the double-layers are such that large biomolecules at the electrodes will be immersed in a pH environment close to the extreme values at the electrode. This means that the charge on the molecules may be controlled as they adsorb onto the electrode; this may prove valuable for the operation of biosensors.
Duration channels mediate human time perception
Authors: Heron James , Aaen-Stockdale Craig , Hotchkiss John , Roach Neil W. , McGraw Paul V. , Whitaker David
Published: August 2011

The task of deciding how long sensory events seem to last is one that the human nervous system appears to perform rapidly and, for sub-second intervals, seemingly without conscious effort. That these estimates can be performed within and between multiple sensory and motor domains suggest time perception forms one of the core, fundamental processes of our perception of the world around us. Given this significance, the current paucity in our understanding of how this process operates is surprising. One candidate mechanism for duration perception posits that duration may be mediated via a system of duration-selective ‘channels’, which are differentially activated depending on the match between afferent duration information and the channels' ‘preferred’ duration. However, this model awaits experimental validation. In the current study, we use the technique of sensory adaptation, and we present data that are well described by banks of duration channels that are limited in their bandwidth, sensory-specific, and appear to operate at a relatively early stage of visual and auditory sensory processing. Our results suggest that many of the computational principles the nervous system applies to coding visual spatial and auditory spectral information are common to its processing of temporal extent.
An Arabidopsis Prenylated Rab Acceptor 1 Isoform, AtPRA1.B6, Displays Differential Inhibitory Effects on Anterograde Trafficking of Proteins at the Endoplasmic Reticulum
Authors: Lee Myoung Hui , Jung Chanjin , Lee Junho , Kim Soo Youn , Lee Yongjik , Hwang Inhwan
Published: August 2011

Prenylated Rab acceptors (PRAs), members of the Ypt-interacting protein family of small membrane proteins, are thought to aid the targeting of prenylated Rabs to their respective endomembrane compartments. In plants, the Arabidopsis (Arabidopsis thaliana) PRA1 family contains 19 members that display varying degrees of sequence homology to animal PRA1 and localize to the endoplasmic reticulum (ER) and/or endosomes. However, the exact role of these proteins remains to be fully characterized. In this study, the effect of AtPRA1.B6, a member of the AtPRA1 family, on the anterograde trafficking of proteins targeted to various endomembrane compartments was investigated. High levels of AtPRA1.B6 resulted in differential inhibition of coat protein complex II vesicle-mediated anterograde trafficking. The trafficking of the vacuolar proteins sporamin:GFP (for green fluorescent protein) and AALP:GFP, the secretory protein invertase:GFP, and the plasma membrane proteins PMP:GFP and H+-ATPase:GFP was inhibited in a dose-dependent manner, while the trafficking of the Golgi-localized proteins ST:GFP and KAM1(ƊC):mRFP was not affected. Conversely, in RNA interference plants displaying lower levels of AtPRA1.B6 transcripts, the trafficking efficiency of sporamin:GFP and AALP:GFP to the vacuole was increased. Localization and N-glycan pattern analyses of cargo proteins revealed that AtPRA1.B6-mediated inhibition of anterograde trafficking occurs at the ER. In addition, AtPRA1.B6 levels were controlled by cellular processes, including 26S proteasome-mediated proteolysis. Based on these results, we propose that AtPRA1.B6 is a negative regulator of coat protein complex II vesicle-mediated anterograde trafficking for a subset of proteins at the ER.
A pilot study of scoliosis assessment using radiation free surface topography in children with GMFCS IV and V cerebral palsy
Authors: Sadani S. , Jones C. , Seal A. , Bhakta B. , Hall R. , Levesley M.
Published: August 2011

Background Prevalence of scoliosis in cerebral palsy (CP) parallels the extent of neurological impairment and causes significant morbidity. Monitoring is important but requires regular radiological investigation. Surface topography provides a non‐radiological approach to scoliosis monitoring.

Aim To evaluate validity, reproducibility and feasibility of Quantec® scans to monitor scoliosis in children with severe CP.

Methods Twenty non‐ambulant children with CP, Gross Motor Function Classification System (GMFCS) grade IV/V had clinical, radiological and Quantec spinal assessment. The children were supported during scans using a seating system specifically designed for this study. Validity was assessed by comparing Quantec (Q) angle with gold standard (Cobb angle), reproducibility analysed using Bland–Altman plots and feasibility assessed using a questionnaire.

Results Prevalence of scoliosis on radiological examination was 65%. Of these children, 85% had curves with Cobb angle less than 28°. Quantec scanning was feasible with appropriate postural support. Mean (and standard deviation) for differences between Cobb and Quantec (Q) angle were 0.02° (6.2°) and for Quantec inter‐observer variability were 0.5° (5.8°).

Conclusions Quantec scanning was feasible, reproducible and had good validity when compared with Cobb angle in a supportive seating system. To consolidate these findings a further study needs to be undertaken with larger number of children with Cobb angles between 25° and 45°.
An epidemiological study of sleep quality in adolescents in South China: a school‐based study
Authors: Zhou H‐Q. , Shi W‐B. , Wang X‐F. , Yao M. , Cheng G‐Y. , Chen P‐Y. , Li D‐G.
Published: August 2011

Background  This study explored the prevalence of disturbed sleep and investigated its distribution characteristics and associated factors in adolescents in South China.

Methods  Junior middle school and senior high school students (n= 1221) were recruited from schools in Shanghai, China. Students completed a questionnaire using the Pittsburgh Sleep Quality Index and factors associated with disturbed sleep.

Results  The prevalence of a tendency towards poor sleep was 34.32% [95% confidence interval (CI): 31.66–36.98] with no significant difference between genders. This tendency increased with age, yielding a significant group effect (P < 0.01). In middle school and high school, the propensity towards poor sleep was 31.34% (95% CI: 28.29–34.39) and 42.22% (95% CI: 36.92–47.52) respectively. The factors associated with poor sleep were more television viewing during weekdays [odds ratio (OR): 1.56, CI: 1.36–1.71], more frequent computer/Internet use (OR: 1.25, CI: 1.08–1.39), earlier school starting time (OR: 1.12, CI: 1.07–1.28), and more time on homework during weekdays (OR: 1.78, CI: 1.51–1.98) and weekends (OR: 1.35, CI: 1.21–1.52)

Conclusions  A tendency towards poor sleep is common in adolescents in South China and its incidence increases with age. The factors associated with this phenomenon indicate that poor sleep in adolescents could be improved, at least partly, by reducing the use of visual technologies and by changing school timetables.
Genetic variability in the IL1RN gene and the balance between interleukin (IL)-1 receptor agonist and IL-1β in idiopathic pulmonary fibrosis
Authors: Barlo N P , van Moorsel C H M , Korthagen N M , Heron M , Rijkers G T , Ruven H J T , van den Bosch J M M , Grutters J C
Published: August 2011

Idiopathic pulmonary fibrosis (IPF) is a rapidly progressive interstitial lung disease of unknown aetiology. Interleukin (IL)-1β plays an important role in inflammation and has been associated with fibrotic remodelling. We investigated the balance between IL-1β and IL-1 receptor antagonist (IL-1Ra) in bronchoalveolar lavage fluid (BALF) and serum as well as the influence of genetic variability in the IL1B and IL1RN gene on disease susceptibility and cytokine levels. In 77 IPF patients and 349 healthy controls, single nucleotide polymorphisms (SNPs) in the IL1RN and IL1B genes were determined. Serum and BALF IL-1Ra and IL-1β levels were measured using a multiplex suspension bead array system and were correlated with genotypes. Both in serum and BALF a significantly decreased IL-1Ra/IL-1β ratio was found in IPF patients compared to healthy controls. In the IL1RN gene, one SNP was associated with both the susceptibility to IPF and reduced IL-1Ra/IL-1β ratios in BALF. Our results show that genetic variability in the IL1RN gene may play a role in the pathogenesis of IPF and that this role may be more important than thought until recently. The imbalance between IL-1Ra and IL-1β might contribute to a proinflammatory and pro-fibrotic environment in their lungs.
The mode of reproductive‐derived Spink (serine protease inhibitor Kazal‐type) action in the modulation of mammalian sperm activity
Authors: Ou C.‐M. , Tang J.‐B. , Huang M.‐S. , Sudhakar Gandhi P. S. , Geetha S. , Li S.‐H. , Chen Y.‐H.
Published: August 2011

The reproductive‐derived serine protease inhibitor Kazal‐type (Spink) has been identified in seminal plasma, and Spink–spermatozoa binding has been illustrated in many mammalian species including human. We used mice as experimental animal to study the mode of Spink action in the modulation of mammalian sperm activity. A Spink3‐binding zone was cytochemically stained on the sperm head at apical hook separated from intact acrosome, whether the cells were capacitated or not. The Spink3–spermatozoa binding neither changed the population of cells in the uncapacitated, capacitated and acrosome‐reacted status nor affected the capacitation‐related protein phosphorylation and cell motility enhancement. Despite that, the Spink–spermatozoa interaction resulted in decreasing the intracellular calcium concentration ([Ca2+]i) of the cell head and suppressing both the acrosome reaction induced by Ca+2 ionophore A23187 and the cell fertility. Furthermore, Spink3 seen on the head of spermatozoa in the uterine cavity after coitus could be removed by the trypsin‐like activity in the uterine fluid of oestrous females, and free Spink3 in the uterine cavity suppressed the protease activity. We integrated our data to shed light on the molecular mechanism of how Spink and its inhibiting protease are interplayed to modulate the activity of mammalian spermatozoa during their transit in the reproductive tract.
Weak responses to dietary enrichment in a specialized aphid predator
Authors: HAUGE MIKAEL S. , NIELSEN FREDERIK H. , TOFT SØREN
Published: August 2011

Some ladybeetles are specialist predators of aphids, coccids or other prey, although they often eat a variety of species from their focal prey taxon. In addition, the diet is often supplemented with alternative prey. How larvae of the aphidophagous Coccinella septempunctata L. utilize a non‐aphid alternative prey (fruit‐fly larvae Drosophila melonogaster Meigen) is compared with adequate (i.e. high‐quality) aphid prey provided alone (monotypic diet) or in mixed diets. The alternative prey are presented either nutrient‐enriched (i.e. raised on dog food supplemented medium) or not (raised on pure medium). Ladybird performance (survival, growth and development) is poor on the pure fly larvae diets, and also reduced when given mixed diets compared with the pure aphid diet. Nutrient enrichment of the fly larvae has no positive effects. The physiological background for the differences in food value, as indicated by performance in life‐history parameters, is a strong pre‐ingestive effect (i.e. reduced consumption of fly larvae compared with aphids) and a post‐ingestive effect (i.e. reduced utilization of assimilated larval fly tissue), whereas the assimilation efficiency of the consumed fly larvae is as high as that of aphids. The results show a physiological trade‐off resulting from prey specialization that reduces the possibility of utilizing alternative prey when the availability of aphids is scarce. Connected with this is a high robustness against variation in prey nutrient diversity and composition; the ladybird shows little positive response to dietary mixing (i.e. neither mixing of adequate aphids, nor of aphids and alternative prey) or to nutrient enrichment of prey. This contrasts with the results from generalist predators (spiders), where similar treatments lead to strong effects on life‐history parameters.