bluuebunny/crossref_metadata_2025 huggingface dataset:
Multilevel Governance, Equality and Human Rights: Evaluating the First Decade of Devolution in Wales
Authors: Rees Teresa , Chaney Paul
Published: February 2011

The creation of a ‘regional’ legislature for Wales in 1999 presents the opportunity to evaluate the promotion of equality and human rights in the context of multi-level governance in the UK. A decade on, positive aspects include the political reprioritisation of equalities in policy and law and new forms of representative and discursive politics. However, significant shortcomings are also evident. Overall, the Wales case study suggests that sub-unitary-state legislatures have the potential to tailor equalities policies to meet local needs more effectively, yet progress may be arrested by context-specific factors, as well as those that resonate with the international literature on mainstreaming equalities in the work of government.
Waves in Poynting-flux dominated jets
Authors: Kirk John G. , Mochol Iwona
Published: February 2011

High-energy emission from blazars is thought to arise in a relativistic jet launched by a supermassive black hole. The rapid variability of the emission suggests that structure of length scale smaller than the gravitational radius of the central black hole is imprinted on the jet as it is launched, and modulates the radiation released after it has been accelerated to high Lorentz factor. We describe a mechanism which can account for the acceleration of the jet, and for the rapid variability of the radiation, based on the propagation characteristics of nonlinear waves in charge-starved, polar jets. These exhibit a delayed acceleration phase, that kicks-in when the inertia associated with the wave currents becomes important. The time structure imprinted on the jet at launch modulates the photons produced by the accelerating jet provided that the electromagnetic cascade in the black-hole magnetosphere is not prolific.
Broad emission lines for a negatively spinning black hole
Authors: Dauser T. , Wilms J. , Reynolds C. S. , Brenneman L. W.
Published: February 2011

We present an extended scheme for the calculation of the profiles of emission lines from accretion disks around rotating black holes. The scheme includes disks with angular momenta which are parallel and antiparallel with respect to the black hole's angular momentum, as both configurations are assumed to be stable (King et al. 2005). Based on a Green's function approach, an arbitrary radius dependence of the disk emissivity and arbitrary limb darkening laws can be easily taken into account, while the amount of precomputed data is significantly reduced with respect to other available models. We discuss line shapes for such disks and present a code for modelling observational data with this scheme in X-ray data analysis programs. A detailed discussion will soon be presented in a forthcoming paper (Dauser et al. 2010).
The image jets modeling of gravitationally lensed sources
Authors: Larchenkova Tatiana , Lutovinov Alexander , Lyskova Natalya
Published: February 2011

The jets image modelling of gravitationally lensed sources have been performed. Several basic models of the lens mass distribution were considered, in particular, a singular isothermal ellipsoid, an isothermal ellipsoid with the core, different multi-components models with the galactic disk, halo and bulge. The obtained jet images were compared as with each other as with results of observations. A significant dependence of the Hubble constant on the model parameters was revealed for B0218+357, when the circular structure was took into account.
A lepto-hadronic model for the high energy emission from the jets of FR I radiogalaxies
Authors: Reynoso Matías M. , Medina María C. , Romero Gustavo E.
Published: February 2011

We present a lepto-hadronic model for the VHE emission from the relativistic jets of FR I radiogalaxies. We assume that protons and electrons are accelerated in a compact region near the base of the jet, and they cool emitting multiwavelength radiation as they propagate along the jet. The particle distributions are obtained using an inhomogeneous steady-state transport equation that accounts for the cooling processes as well as the convection of particles in the jet. The dominant processes that contribute to the photon SED are electron and proton synchrotron radiation, inverse Compton interactions, and the inelastic collisions pp and pγ. The accompanying neutrino output is obtained and the possibility of detection with Km3Net and IceCube is discussed for the cases of Cen A and M87.
Analysing VLBI images of astrophysical jets via cross-entropy global optimisation method
Authors: Caproni Anderson , Monteiro Hektor , Abraham Zulema
Published: February 2011

Most of jets detected in AGN blazar sources exhibit a morphological structure usually composed by a spatially unresolved core and jet knots receding from it at relativistic velocities. In some cases, the trajectories of the jet components on the plane of the sky seem to be bent, indicating the existence of some kind of acceleration in the respective motion. However, such claims depend strongly on the correct determination of the structural parameters of the jet components, usually obtained from model fitting procedures performed either in the (u,v) or in the image planes. In this work we introduce a new model fitting technique to obtain structural parameters of knots present in VLBI jet images. Our method that is based on the cross-entropy technique minimises an performance function that depends on the sum of the squared residuals obtained from the comparison of an VLBI image and a model image, constructed by summing Ns elliptical Gaussian synthetic sources. We present in this work the cross-entropy model fittings of benchmark images that were built to simulate most of the conditions encountered in typical VLBI images of active galactic nuclei. Besides recovering the parameters of the jet components in all validation tests, our method is able to point out quantitatively the number of the sources present in the image.
Testing the blazar sequence and black hole mass scaling with BL Lac objects
Authors: Plotkin Richard M. , Markoff Sera , Anderson Scott F. , Kelly Brandon C. , Körding Elmar , Trager Scott C.
Published: February 2011

Jets from accreting black holes appear remarkably similar over eight orders of magnitude in black hole mass, with more massive black holes generally launching more powerful jets. For example, there is an observed correlation, termed the fundamental plane of black hole accretion, between black hole mass, radio luminosity, and X-ray luminosity. Here, we probe the high-mass tail (108–109M⊙) of the accreting black hole distribution with BL Lac objects. We build SEDs for hundreds of SDSS BL Lacs, and we use these SEDs to test the blazar sequence, a proposed anti-correlation between jet power and peak frequency. We then show our BL Lacs fit on the fundamental plane, supporting the non-linear scaling of jet radiation with black hole mass. The subset of BL Lacs considered here compose the largest sample yet used in the above types of studies, reducing potential selection effects and biases.
Nonthermal processes in microquasars
Authors: Bosch-Ramon Valentí
Published: February 2011

Microquasars are X-ray binaries that show extended radio jets. These jets can accelerate particles up to relativistic energies that produce non-thermal emission from radio to TeV, and could also make a non-negligible contribution to the galactic CRs in some energy ranges. The orbital motion and compactness of these sources allow the study of high-energy astrophysical phenomena in extreme conditions that change in accessible timescales. In this work, I briefly discuss the production of broadband non-thermal emission in microquasars, putting special emphasis on the high- and the very high-energy bands.
Jet launching and field advection in quasi-Keplerian discs
Authors: Ferreira Jonathan , Petrucci Pierre Olivier
Published: February 2011

The fact that self-confined jets are observed around black holes, neutron stars and young forming stars points to a jet launching mechanism independent of the nature of the central object, namely the surrounding accretion disc. The properties of Jet Emitting Discs (JEDs) are briefly reviewed. It is argued that, within an alpha prescription for the turbulence (anomalous viscosity and diffusivity), the steady-state problem has been solved. Conditions for launching jets are very stringent and require a large scale magnetic field Bz close to equipartition with the total (gas and radiation) pressure. The total power feeding the jets decreases with the disc thickness: fat ADAF-like structures with h ~ r cannot drive super-Alfvénic jets. However, there exist also hot, optically thin JED solutions that would be observationally very similar to ADAFs.

Finally, it is argued that variations in the large scale magnetic Bz field is the second parameter required to explain hysteresis cycles seen in LMXBs (the first one would be Ṁa).
Transient high-energy flares from accreting black holes
Authors: Vieyro Florencia L. , Romero Gustavo E.
Published: February 2011

We present a model for high-energy flares in accreting black holes based on the injection in a magnetized corona of a non-thermal population of relativistic particles. Coupled transport equations are solved for all species of particles and the electromagnetic and neutrino output is predicted for the case of Galactic black holes.
Isolating the jet in broadband spectra of XBs
Authors: Russell David M. , Lewis Fraser , Maitra Dipankar , Dunn Robert J. H. , Markoff Sera , Jonker Peter G. , Linares Manuel , Tudose Valeriu
Published: February 2011

Most accretion-powered relativistic jet sources in our Galaxy are transient X-ray binaries (XBs). Efforts to coordinate multiwavelength observations of these objects have improved dramatically over the last decade. Now the challenge is to interpret broadband spectral energy distributions (SEDs) of XBs that are well sampled in both wavelength and time. Here we focus on the evolution of the jet in their broadband spectra. Some of the most densely sampled broadband SEDs of a neutron star transient (IGR J00291+5934) are used to constrain the optically thick–thin break in the jet spectrum. For the black hole transient XTE J1550-564, infrared – X-ray correlations, evolution of broadband spectra and timing signatures indicate that synchrotron emission from the jet likely dominates the X-ray power law at low luminosities (~(2 × 10−4 − 2 × 10−3) LEdd) during the hard state outburst decline.
Radiative MHD simulations of the jets from RW Aurigae
Authors: Teşileanu Ovidiu , Mignone Andrea , Massaglia Silvano , Stute Matthias
Published: February 2011

The MHD simulations of stellar jets recently included complex models of radiative emission computation, allowing for better predictions in terms of emission line ratios. Employing also Adaptive Mesh Refinement, the large-scale propagation of jets could be followed. The simulation of multiple shockwaves originating in perturbations close to the jet origin and travelling along the jet beam allows for the construction of synthetic emission maps at various wavelengths, to be directly compared to observations. We apply this procedure for the jets originating from RW Aurigae.
Real‐time beamforming using high‐speed FPGAs at the Allen Telescope Array
Authors: Barott William C. , Milgrome Oren , Wright Melvyn , MacMahon David , Kilsdonk Tom , Backus Peter , Dexter Matt
Published: February 2011

The Allen Telescope Array (ATA) at the Hat Creek Radio Observatory (HCRO) is a wide‐field panchromatic radio telescope currently consisting of 42 offset‐Gregorian antennas each with a 6 m aperture, with plans to expand the array to 350 antennas. Through unique back‐end hardware, the ATA performs real‐time wideband beamforming with independent subarray capabilities and customizable beam shaping. The beamformers enable science observations requiring the full gain of the array, time domain (nonintegrated) output, and interference excision or orthogonal beamsets. In this paper we report on the design of this beamformer, including architecture and experimental results. Furthermore, we address some practical considerations in large‐N wideband beamformers implemented on field programmable gate array platforms, including device utilization, methods of calibration and control, and interchip synchronization.
Orbifold singularities, Lie algebras of the third kind (LATKes), and pure Yang–Mills with matter
Authors: Friedmann Tamar
Published: February 2011

We discover the unique, simple Lie algebra of the third kind, or LATKe, that stems from codimension 6 orbifold singularities and gives rise to a new kind of Yang–Mills theory which simultaneously is pure and contains matter. The root space of the LATKe is one-dimensional and its Dynkin diagram consists of one point. The uniqueness of the LATKe is a vacuum selection mechanism. \documentclass[12pt]{minimal}\begin{document}\[\begin{array}{c}\hbox{The World in a Point?}\\[12pt]\hbox{Blow-up of} C^3/Z_3|\,\, \hbox{Dynkin diagram of the LATKe}\\[12pt]\bullet \\[12pt]\hbox{Pure Yang-Mills with matter}\end{array}\]\end{document}TheWorldinaPoint?Blow-upofC3/Z3|DynkindiagramoftheLATKe●PureYang-Millswithmatter
Work function measurements during plasma exposition at conditions relevant in negative ion sources for the ITER neutral beam injection
Authors: Gutser R. , Wimmer C. , Fantz U.
Published: February 2011

Cesium seeded sources for surface generated negative hydrogen ions are major components of neutral beam injection systems in future large-scale fusion experiments such as ITER. The stability and delivered current density depend highly on the work function during vacuum and plasma phases of the ion source. One of the most important quantities that affect the source performance is the work function. A modified photocurrent method was developed to measure the temporal behavior of the work function during and after cesium evaporation. The investigation of cesium exposed Mo and MoLa samples under ITER negative hydrogen ion based neutral beam injection relevant surface and plasma conditions showed the influence of impurities which result in a fast degradation when the plasma exposure or the cesium flux onto the sample is stopped. A minimum work function close to that of bulk cesium was obtained under the influence of the plasma exposition, while a significantly higher work function was observed under ITER-like vacuum conditions.
Modeling molecular effects on plasmon transport: Silver nanoparticles with tartrazine
Authors: Arntsen Christopher , Lopata Kenneth , Wall Michael R. , Bartell Lizette , Neuhauser Daniel
Published: February 2011

Modulation of plasmon transport between silver nanoparticles by a yellow fluorophore, tartrazine, is studied theoretically. The system is studied by combining a finite-difference time-domain Maxwell treatment of the electric field and the plasmons with a time-dependent parameterized method number 3 simulation of the tartrazine, resulting in an effective Maxwell/Schrödinger (i.e., classical/quantum) method. The modeled system has three linearly arranged small silver nanoparticles with a radius of 2 nm and a center-to-center separation of 4 nm; the molecule is centered between the second and third nanoparticles. We initiate an x-polarized current on the first nanoparticle and monitor the transmission through the system. The molecule rotates much of the x-polarized current into the y-direction and greatly reduces the overall transmission of x-polarized current.
Features of ferromagnetic resonance in nanogranular films with perpendicular anisotropy of particles
Authors: Ryabchenko S. M. , Timopheev A. A. , Kalita V. M. , Stognei O. V. , Sitnikov A. V.
Published: February 2011

Ferromagnetic resonance (FMR) in the blocked state of nanogranular magnetic films with perpendicular anisotropy of granules is considered for the magnetic field, which is perpendicular to the film plane, for the field strengths corresponding to the unsaturated magnetic state of the films. It is shown that in this case FMR response of the film is the sum of contributions from two subensembles of granules with the magnetic moments oriented “up” and “down” with respect to the film plane. These subensembles are coupled through the common demagnetization field of the film. It is established that FMR signals registered with the help of microwave detector direct current and a component of the detector current at the frequency of radiospectrometer magnetic field high frequency modulation are essentially different. It is shown that the distinction arises due to the fact that total magnetization of each of the subensembles and the film as a whole are practically not modulated by the high frequency modulation of the quasistatic magnetic field in the conditions of the ensemble blocked state and for the amplitude of modulation substantially smaller than the coercive field. Results of the phenomenon consideration within a simplified model are in a satisfactory qualitative agreement with the FMR measurement data for a Co0.54(Al2O3)0.46 film, basic characteristics of which satisfy requirements of the model.
The effect of He plasma treatment on properties of organosilicate glass low-k films
Authors: Braginsky O. V. , Kovalev A. S. , Lopaev D. V. , Malykhin E. M. , Mankelevich Yu. A. , Proshina O. V. , Rakhimova T. V. , Rakhimov A. T. , Voloshin D. G. , Vasilieva A. N. , Zyryanov S. M. , Smirnov E. A. , Baklanov M. R.
Published: February 2011

The effect of low-pressure He plasma on properties of nanoporous organosilicate glasses low-k films with 24% and 33% open porosity is studied. The influence of ions, VUV radiation, and metastable atoms are extracted separately using a special experimental system designed for this purpose. The low-k films treated in He plasma were exposed to O or H atoms in the downstream of high-pressure O2 or H2 rf discharge. The changes in chemical composition and structure occurring in low-k films were measured before and after all treatments. The loss probabilities of oxygen and hydrogen atoms on the low-k film surface were measured for both treated and pristine films. It is shown that the film pretreatment in He plasma leads to the noticeable densification of the top surface layer up to complete sealing all the films studied. The sealing layer prevents O atoms from deep penetration to the film bulk and carbon extraction. The sealing mechanism related to the joint impact of low-energy ions and VUV photons with metastable atoms in He plasma is discussed in detail.
Strain relief and AlSb buffer layer morphology in GaSb heteroepitaxial films grown on Si as revealed by high-angle annular dark-field scanning transmission electron microscopy
Authors: Vajargah S. Hosseini , Couillard M. , Cui K. , Tavakoli S. Ghanad , Robinson B. , Kleiman R. N. , Preston J. S. , Botton G. A.
Published: February 2011

The interfacial misfit (IMF) dislocation array of an epitaxial GaSb film on a Si substrate has been imaged with high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The mismatch strain accommodation through dislocation formation has been investigated using geometric phase analysis (GPA) on HAADF-STEM images with atomic resolution to probe the defects’ local strain distribution. These measurements indicate that the lattice parameter of the epitaxial film recovers its bulk value within three unit cells from the interface due to the relaxation through IMF dislocations. The atomic number contrast of the HAADF-STEM images and energy dispersive x-ray spectrometry illustrate the formation of islands of AlSb buffer layer along the interface. The role of the AlSb buffer layer in facilitating the GaSb film growth on Si is further elucidated by investigating the strain field of the islands with the GPA.
Coherent control of the isomerization of retinal in bacteriorhodopsin in the high intensity regime
Authors: Prokhorenko Valentyn I. , Halpin Alexei , Johnson Philip J. M. , Miller R. J. Dwayne , Brown Leonid S.
Published: February 2011

Coherent control protocols provide a direct experimental determination of the relative importance of quantum interference or phase relationships of coupled states along a selected pathway. These effects are most readily observed in the high intensity regime where the field amplitude is sufficient to overcome decoherence effects. The coherent response of retinal photoisomerization in bacteriorhodopsin to the phase of the photoexcitation pulses was examined at fluences of 1015 – 2.5 × 1016 photons per square centimeter, comparable to or higher than the saturation excitation level of the S0 − S1 retinal electronic transition. At moderate excitation levels of ∼6 × 1015 photons/cm2 (<100 GW/cm2), chirping the excitation pulses increases the all-trans to 13-cis isomerization yield by up to 16% relative to transform limited pulses. The reported results extend previous weak-field studies [Prokhorenko et al., Science 313, 1257 (2006)] and further illustrate that quantum coherence effects persist along the reaction coordinate in strong fields even for systems as complex as biological molecules. However, for higher excitation levels of ∼200 GW/cm2, there is a dramatic change in photophysics that leads to multiphoton generated photoproducts unrelated to the target isomerization reaction channel and drastically changes the observed isomerization kinetics that appears, in particular, as a red shift of the transient spectra. These results explain the apparent contradictions of the work by Florean et al. [Proc. Natl. Acad. Sci. U.S.A. 106, 10896 (2009)] in the high intensity regime. We are able to show that the difference in observations and interpretation is due to artifacts associated with additional multiphoton-induced photoproducts. At the proper monitoring wavelengths, coherent control in the high intensity regime is clearly observable. The present work highlights the importance of conducting coherent control experiments in the low intensity regime to access information on quantum interference effects along specific reaction coordinates.
Room temperature circularly polarized lasing in an optically spin injected vertical-cavity surface-emitting laser with (110) GaAs quantum wells
Authors: Iba Satoshi , Koh Shinji , Ikeda Kazuhiro , Kawaguchi Hitoshi
Published: February 2011

We fabricated a (110)-oriented vertical-cavity surface-emitting laser (VCSEL) with GaAs/AlGaAs quantum wells (QWs) and characterized the lasing properties of the VCSEL under optical spin injection. We demonstrated circularly polarized lasing at a high degree of circular polarization of 0.96 for our VCSEL at room temperature that originated from a long electron spin relaxation time of 0.7 ns in the (110) GaAs QWs despite a really small initial electron spin polarization of 0.04, which was well reproduced by using a rate equation analysis.
On the fluctuating wall-shear stress in zero pressure-gradient turbulent boundary layer flows
Authors: Örlü Ramis , Schlatter Philipp
Published: February 2011

Recent direct numerical simulation (DNS) results relating to the behavior of the fluctuating wall-shear stress τw,rms+ in turbulent boundary layer flows are discussed. This new compilation is motivated by a recent article [Wu and Moin, “Transitional and turbulent boundary layer with heat transfer,” Phys. Fluids 22, 085105 (2010)], which indicates a need for clarification of the value of τw,rms+. It is, however, shown here, based on other recent DNS data, that most results, both in boundary layer and channel geometry, yield τw,rms+≈0.4 plus a small increase with Reynolds number coming from the growing influence of the outer spectral peak. The observed discrepancy in experimental data is mainly attributed to spatial resolution effects, as originally described by Alfredsson et al. [“The fluctuating wall-shear stress and the velocity field in the viscous sublayer,” Phys. Fluids 31, 1026 (1988)].
Water Interaction with native defects on rutile TiO2 nanowire: Ab initio calculations
Authors: Nisar J. , Araujo C. Moyses , Ahuja R.
Published: February 2011

Adsorption of water molecules on stoichiometric and defective surfaces of rutile TiO2 nanowire oriented along the [1¯10] direction is investigated using density function theory calculations. We have investigated, in particular, O and Ti vacancies where energetic, structural, and electronic properties were evaluated. It was found that the water molecules interacting with O-vacancy undergo spontaneous dissociation, forming hydroxyl groups bound to Ti atoms and other OH groups formed by surface O and H-water. The same is not found in the case of perfect and Ti-vacancy containing nanowire. This dissociation of water molecules is due to charge transfer from neighboring Ti atom, which is polarized due to the O-vacancy.
Accelerating the convergence of path integral dynamics with a generalized Langevin equation
Authors: Ceriotti Michele , Manolopoulos David E. , Parrinello Michele
Published: February 2011

The quantum nature of nuclei plays an important role in the accurate modelling of light atoms such as hydrogen, but it is often neglected in simulations due to the high computational overhead involved. It has recently been shown that zero-point energy effects can be included comparatively cheaply in simulations of harmonic and quasiharmonic systems by augmenting classical molecular dynamics with a generalized Langevin equation (GLE). Here we describe how a similar approach can be used to accelerate the convergence of path integral (PI) molecular dynamics to the exact quantum mechanical result in more strongly anharmonic systems exhibiting both zero point energy and tunnelling effects. The resulting PI-GLE method is illustrated with applications to a double-well tunnelling problem and to liquid water.
Controlled self-modulation of high energy beams in a plasma
Authors: Lotov K. V.
Published: February 2011

A high energy particle beam propagating in a uniform plasma is subject to the transverse two-stream instability that first transforms the beam into the train of microbunches and then quickly destroys that train by transverse wakefields. By the proper longitudinal inhomogeneity of the plasma density, it is possible to stop the instability action at the stage of microbunches and form the bunch train that can resonantly excite plasma wakefields over a long distance. The latter feature is vital for proton beam driven plasma wakefield acceleration that was recently proposed as a way to bring electrons to TeV energy range in a single plasma section.
On the relation between virial coefficients and the close-packing of hard disks and hard spheres
Authors: Maestre Miguel Ángel G. , Santos Andrés , Robles Miguel , de Haro Mariano López
Published: February 2011

The question of whether the known virial coefficients are enough to determine the packing fraction η∞ at which the fluid equation of state of a hard-sphere fluid diverges is addressed. It is found that the information derived from the direct Padé approximants to the compressibility factor constructed with the virial coefficients is inconclusive. An alternative approach is proposed which makes use of the same virial coefficients and of the equation of state in a form where the packing fraction is explicitly given as a function of the pressure. The results of this approach both for hard-disk and hard-sphere fluids, which can straightforwardly accommodate higher virial coefficients when available, lends support to the conjecture that η∞ is equal to the maximum packing fraction corresponding to an ordered crystalline structure.
Concave and Convex Phases in Ambiguous Figures Showing Colour Shifts. Mach's Figure and the Ambegujas Phenomenon
Authors: Bergström Sten Sture , Gustafsson Karl-Arne
Published: February 2011

Two ambiguous figures (Mach's book-figure and the AMBEGUJAS phenomenon) have been studied. They show colour shifts synchronised with the shifts of their alternative phases. The perceived concave phase appeared to have chromatic surface colour, but the perceived convex phase can appear to be in coloured illumination and shadow (film colour). The two perceived reversible shapes of the Mach figure (the book and the tent) and the three perceived alternative shapes of the Mondrians used in the AMBEGUJAS phenomenon (a roof, a ceiling, and a tile) all can appear to have chromatic surface colours in their concave phases but appear to have coloured illumination and shadow in their convex phases.
An Antisymmetric Psychometric Function on a Logarithmic Scale
Authors: Tiest Wouter M Bergmann , Kappers Astrid M L
Published: February 2011

This very brief report introduces a psychometric function, very suitable for psychophysical data that displays Weber-like behaviour, because it is antisymmetric on a logarithmic scale.
Analysis of natural allelic variation in
Arabidopsis
using a multiparent recombinant inbred line population
Authors: Huang Xueqing , Paulo Maria-João , Boer Martin , Effgen Sigi , Keizer Paul , Koornneef Maarten , van Eeuwijk Fred A.
Published: February 2011

To exploit the diversity in
Arabidopsis thaliana
, eight founder accessions were crossed to produce six recombinant inbred line (RIL) subpopulations, together called an
Arabidopsis
multiparent RIL (AMPRIL) population. Founders were crossed pairwise to produce four F1 hybrids. These F1s were crossed according to a diallel scheme. The resulting offspring was then selfed for three generations. The F4 generation was genotyped with SNP and microsatellite markers. Data for flowering time and leaf morphology traits were determined in the F5 generation. Quantitative trait locus (QTL) analysis for these traits was performed using especially developed mixed-model methodology, allowing tests for QTL main effects, QTL by background interactions, and QTL by QTL interactions. Because RILs were genotyped in the F4 generation and phenotyped in the F5 generation, residual heterozygosity could be used to confirm and fine-map a number of the QTLs in the selfed progeny of lines containing such heterozygosity. The AMPRIL population is an attractive resource for the study of complex traits.
Characterization of active waveguides fabricated by ultralow-fluence swift heavy ion irradiation in lithium niobate crystals
Authors: Dong Ningning , Chen Feng , Jaque Daniel , Benayas Antonio , Qiu Feng , Narusawa Tadashi
Published: February 2011

We report on the fabrication of neodymium-doped lithium niobate active planar waveguides based on the generation of non-overlapping nano-tracks by ultralow-fluence swift heavy ions. A combination of confocal luminescence, Raman and surface second harmonic investigations have evidenced the simultaneous presence of partial amorphization, damage and local compression of the lithium niobate network along the ion path, with these effects being at the basis of the refractive index modification. The potential application of the obtained waveguides in multi-functional laser devices has been discussed.
Impedance spectroscopy analysis of Ba0.7Sr03TiO3/La0.7Sr0.3MnO3 heterostructure
Authors: Martínez R , Kumar A , Palai R , Scott J F , Katiyar R S
Published: February 2011

Impedance spectroscopy technique has been used to study the effect of grains and grain boundaries in a heterostructure constituted with ferromagnetic La0.7Sr0.3MnO3 (LSMO) and ferroelectric Ba0.7Sr0.3TiO3 (BST) layers grown by pulsed laser deposition technique on (1 0 0) oriented MgO substrate. Frequency and temperature dependence of the complex impedance and complex electric modulus were measured in (BST20u.c,/LSMO10u.c
)25 over a temperature range of 360–500 K. Non-Debye relaxation was observed in the investigated system. An equivalent circuit and the modified constant phase element circuit were used to describe the impedance spectroscopy, and excellent agreement between the calculated and measured curves was obtained from each model. The activation energy (∼0.25 eV–0.48 eV) has been obtained from Arrhenius fitting of different relaxation processes present in the material, and its characteristic values support a model of Maxwell–Wagner relaxation in the heterostructured film at elevated temperatures and in the low frequency range. The electrical ac and dc conductivity studies showed that the heterostructure possesses negative temperature coefficient of resistance properties. It was found that the resistance of grain boundaries was larger than the resistance of intra-grains.
Piezoelectrets from sandwiched porous polytetrafluoroethylene (ePTFE) films: influence of porosity and geometry on charging properties
Authors: Zhukov Sergey , Fedosov Sergey , von Seggern Heinz
Published: February 2011

Sandwiched structures of open-porous and solid polymer dielectrics reveal a strong piezoelectric response after proper charging by high electric fields. Here, the electrical properties of corona-poled three-layer FEP/ePTFE/FEP sandwiches are studied theoretically and experimentally with the objective of its possible optimization for the highest piezoelectric activity. Modelling of the charging properties is performed for different sandwich geometries. It is shown that the maximum value of the remanent interface charge density accumulated during poling depends mainly on the ratio of the solid and porous layers thicknesses and on parameter E
B, which characterizes the electric breakdown strength of air in the porous layer. E
B exhibits specific dependences on porosity and thickness of the porous layer. For a given porous layer E
B is independent of the solid film thickness. The obtained results can be utilized to further optimize the sandwich structure as an electromechanically active device.
Lumenal interactions in nuclear pore complex assembly and stability
Authors: Yewdell William T. , Colombi Paolo , Makhnevych Taras , Lusk C. Patrick
Published: February 2011

Nuclear pore complexes (NPCs) provide a gateway for the selective transport of macromolecules across the nuclear envelope (NE). Although we have a solid understanding of NPC composition and structure, we do not have a clear grasp of the mechanism of NPC assembly. Here, we demonstrate specific defects in nucleoporin distribution in strains lacking Heh1p and Heh2p—two conserved members of the LEM (Lap2, emerin, MAN1) family of integral inner nuclear membrane proteins. These effects on nucleoporin localization are likely of functional importance as we have defined specific genetic interaction networks between HEH1 and HEH2, and genes encoding nucleoporins in the membrane, inner, and outer ring complexes of the NPC. Interestingly, expression of a domain of Heh1p that resides in the NE lumen is sufficient to suppress both the nucleoporin mislocalization and growth defects in heh1Δpom34Δ strains. We further demonstrate a specific physical interaction between the Heh1p lumenal domain and the massive cadherin-like lumenal domain of the membrane nucleoporin Pom152p. These findings support a role for Heh1p in the assembly or stability of the NPC, potentially through the formation of a lumenal bridge with Pom152p.
Osteoblast connexin43 modulates skeletal architecture by regulating both arms of bone remodeling
Authors: Watkins Marcus , Grimston Susan K. , Norris Jin Yi , Guillotin Bertrand , Shaw Angela , Beniash Elia , Civitelli Roberto
Published: February 2011

Connexin43 (Cx43) has an important role in skeletal homeostasis, and Cx43 gene (Gja1) mutations have been linked to oculodentodigital dysplasia (ODDD), a human disorder characterized by prominent skeletal abnormalities. To determine the function of Cx43 at early steps of osteogenesis and its role in the ODDD skeletal phenotype, we have used the Dermo1 promoter to drive Gja1 ablation or induce an ODDD mutation in the chondro-osteogenic linage. Both Gja1 null and ODDD mutant mice develop age-related osteopenia, primarily due to a progressive enlargement of the medullary cavity and cortical thinning. This phenotype is the consequence of a high bone turnover state, with increased endocortical osteoclast-mediated bone resorption and increased periosteal bone apposition. Increased bone resorption is a noncell autonomous defect, caused by exuberant stimulation of osteoclastogenesis by Cx43-deficient bone marrow stromal cells, via decreased Opg production. The latter is part of a broad defect in osteoblast differentiation and function, which also results in abnormal structural and material properties of bone leading to decreased resistance to mechanical load. Thus Cx43 in osteogenic cells is a critical regulator of both arms of the bone remodeling cycle, its absence causing structural changes remindful of aged or disused bone.
Gfer inhibits Jab1-mediated degradation of p27kip1to restrict proliferation of hematopoietic stem cells
Authors: Teng Ellen C. , Todd Lance R. , Ribar Thomas J. , Lento William , Dimascio Leah , Means Anthony R. , Sankar Uma
Published: February 2011

Growth factor erv1-like (Gfer) is an evolutionarily conserved sulfhydryl oxidase that is enriched in embryonic and adult stem cells and plays an essential prosurvival role in pluripotent embryonic stem cells. Here we show that knockdown (KD) of Gfer in hematopoietic stem cells (HSCs) compromises their in vivo engraftment potential and triggers a hyper-proliferative response that leads to their exhaustion. KD of Gfer in HSCs does not elicit a significant alteration of mitochondrial morphology or loss of cell viability. However, these cells possess significantly reduced levels of the cyclin-dependent kinase inhibitor p27kip1. In contrast, overexpression of Gfer in HSCs results in significantly elevated total and nuclear p27kip1. KD of Gfer results in enhanced binding of p27kip1to its inhibitor, the COP9 signalosome subunit jun activation-domain binding protein 1 (Jab1), leading to its down-regulation. Conversely, overexpression of Gfer results in its enhanced binding to Jab1 and inhibition of the Jab1-p27kip1interaction. Furthermore, normalization of p27kip1in Gfer-KD HSCs rescues their in vitro proliferation deficits. Taken together, our data demonstrate the presence of a novel Gfer-Jab1-p27kip1pathway in HSCs that functions to restrict abnormal proliferation.
BiC: a web server for calculating bimodality of coexpression between gene and protein networks
Authors: Linderman George C. , Patel Vishal N. , Chance Mark R. , Bebek Gurkan
Published: February 2011

Summary: Bimodal patterns of expression have recently been shown to be useful not only in prioritizing genes that distinguish phenotypes, but also in prioritizing network models that correlate with proteomic evidence. In particular, subgroups of strongly coexpressed gene pairs result in an increased variance of the correlation distribution. This variance, a measure of association between sets of genes (or proteins), can be summarized as the bimodality of coexpression (BiC). We developed an online tool to calculate the BiC for user-defined gene lists and associated mRNA expression data. BiC is a comprehensive application that provides researchers with the ability to analyze both publicly available and user-collected array data.

Availability: The freely available web service and the documentation can be accessed at http://gurkan.case.edu/software.

Contact:  gurkan@case.edu
Molecular characterization of a new species in the genus Alphacoronavirus associated with mink epizootic catarrhal gastroenteritis
Authors: Vlasova Anastasia N. , Halpin Rebecca , Wang Shiliang , Ghedin Elodie , Spiro David J. , Saif Linda J.
Published: February 2011

A coronavirus (CoV) previously shown to be associated with catarrhal gastroenteritis in mink (Mustela vison) was identified by electron microscopy in mink faeces from two fur farms in Wisconsin and Minnesota in 1998. A pan-coronavirus and a genus-specific RT-PCR assay were used initially to demonstrate that the newly discovered mink CoVs (MCoVs) were members of the genus Alphacoronavirus. Subsequently, using a random RT-PCR approach, full-genomic sequences were generated that further confirmed that, phylogenetically, the MCoVs belonged to the genus Alphacoronavirus, with closest relatedness to the recently identified but only partially sequenced (fragments of the polymerase, and full-length spike, 3c, envelope, nucleoprotein, membrane, 3x and 7b genes) ferret enteric coronavirus (FRECV) and ferret systemic coronavirus (FRSCV). The molecular data presented in this study provide the first genetic evidence for a new coronavirus associated with epizootic catarrhal gastroenteritis outbreaks in mink and demonstrate that MCoVs possess high genomic variability and relatively low overall nucleotide sequence identities (91.7 %) between contemporary strains. Additionally, the new MCoVs appeared to be phylogenetically distant from human (229E and NL63) and other alphacoronaviruses and did not belong to the species Alphacoronavirus 1. It is proposed that, together with the partially sequenced FRECV and FRSCV, they comprise a new species within the genus Alphacoronavirus.
Characterization and purification of recombinant bovine viral diarrhea virus particles with epitope-tagged envelope proteins
Authors: Wegelt Anne , Reimann Ilona , Granzow Harald , Beer Martin
Published: February 2011

Bovine viral diarrhea virus (BVDV) belongs to the genus Pestivirus within the family Flaviviridae. The lipid membrane of the virions is supposed to contain the three glycosylated envelope proteins Erns, E1 and E2, but detailed studies of virus assembly are complicated because no efficient purification method for pestiviruses has been described so far. In this study, we generated infectious BVDV with N-terminally FLAG-tagged Erns or E2 proteins, respectively. The expression of the epitope-tagged Erns and E2 proteins could be shown by immunofluorescence and Western blot experiments. Furthermore, an affinity tag purification protocol for the isolation and concentration of infectious BVDV was established. In the preparation with a titre of 108.75 TCID50 ml−1, spherical particles with a diameter of 43–58 nm (mean diameter: 48 nm) could be detected by negative staining electron microscopy, and immunogold labelling located both Erns and E2 proteins at the virus membrane.
Porcine reproductive and respiratory syndrome virus in Ontario, Canada 1999 to 2010: genetic diversity and restriction fragment length polymorphisms
Authors: Brar Manreetpal Singh , Shi Mang , Ge Li , Carman Susy , Murtaugh Michael P. , Leung Frederick Chi-Ching
Published: February 2011

Classification of Ontario porcine reproductive and respiratory syndrome virus (PRRSV) field isolates (n = 505) from 1999 to 2010, based on a global type 2 PRRSV ORF5 phylogenetic framework, revealed genetic diversity comparable to PRRSV in the USA, with sequences assigned to five of nine lineages (1, 2, 5, 8 and 9). Importantly, the tree topology indicated a Canadian ancestry for the highly virulent MN184-related strains that first emerged in 2001 in the USA. Mapping of the RFLP patterns onto the phylogenetic tree revealed numerous examples of different RFLP patterns located within the same phylogenetic cluster. Statistical analysis showed occurrences where similar RFLP patterns masked diverse genetic distances and instances of close genetic proximity with divergent RFLP patterns. Collectively, extensive genetic diversity prevails in type 2 PRRSV in one region of the North American swine industry, and it is not described adequately by RFLP typing, which might have value in differentiating strains at the local farm level.
Subregion-specific p300 conditional knock-out mice exhibit long-term memory impairments
Authors: Oliveira Ana M.M. , Estévez Marcel A. , Hawk Joshua D. , Grimes Shannon , Brindle Paul K. , Abel Ted
Published: February 2011

Histone acetylation plays a critical role during long-term memory formation. Several studies have demonstrated that the histone acetyltransferase (HAT) CBP is required during long-term memory formation, but the involvement of other HAT proteins has not been extensively investigated. The HATs CBP and p300 have at least 400 described interacting proteins including transcription factors known to play a role in long-term memory formation. Thus, CBP and p300 constitute likely candidates for transcriptional coactivators in memory formation. In this study, we took a loss-of-function approach to evaluate the role of p300 in long-term memory formation. We used conditional knock-out mice in which the deletion of p300 is restricted to the postnatal phase and to subregions of the forebrain. We found that p300 is required for the formation of long-term recognition memory and long-term contextual fear memory in the CA1 area of the hippocampus and cortical areas.
Conservation of Galápagos land iguanas: genetic monitoring and predictions of a long‐term program on the island of Santa Cruz
Authors: Fabiani A. , Trucchi E. , Rosa S. , Marquez C. , Snell H. L. , Snell H. M. , Tapia Aguilera W. , Gentile G.
Published: February 2011

The distribution of the Galápagos land iguanas Conolophus subcristatus has been strongly affected by human activities in the last century. Previously widespread throughout the whole archipelago, today they inhabit only few islands, with populations often small and isolated. In this study, we analyzed the population genetic structure of land iguanas from Santa Cruz Island to investigate the genetic implications of a semi‐captive conservation program that started in middle 1970s and is still ongoing. Nine microsatellites were used to measure the level of genetic variability and to detect potential evidence of inbreeding and genetic sub‐structure. Furthermore, we used approximate Bayesian computation, together with software packages for coalescent‐based simulations, to test a priori hypotheses in different demographic scenarios. Despite the abrupt reduction in size of the original population, no evidence of inbreeding was found, and the levels of genetic variability were similar to those of undisturbed populations of the archipelago. Nevertheless, the source and the repatriated populations started differentiating (FST=0.016) and genetic sub‐structure was found. Following our results and the simulation of possible future scenarios, we suggest the genetic measures that should be adopted to avoid further genetic variability depletion and preserve this vulnerable endemic species.
Coopetitive Buyer–Supplier Relationship: An Investigation of Bargaining Power, Relational Context, and Investment Strategies
Authors: Nair Anand , Narasimhan Ram , Bendoly Elliot
Published: February 2011

This study proposes an analytical approach combined with a behavioral experiment for a joint examination of the competitive and cooperative (i.e., coopetitive) relationship between a buyer and a supplier. Specifically, the article considers the scenario in which the buyer and the supplier invest in strategic capabilities to increase their relative bargaining power. The article examines how dynamic investments in strategic assets are influenced by the locus of bargaining power and by the underlying context (synergistic vs. adversarial) of the interfirm relationship. The dynamic evolution of bargaining power is also examined. A dynamic game model is considered to examine the evolution of investment strategies in critical resources and to investigate the issues of bargaining power in a buyer–supplier dyad. Equilibrium expressions for the investment strategies of the buyer and the supplier are presented and their implications for buyer–supplier relationships are examined. The behavioral experiment complements the analytical model and examines the correspondence between optimal behavior suggested by the analytical model and the boundedly rational behavior of decision makers in an experimental context. The results from the model and behavioral experiments suggest that the strategies are a function of the risk‐adjusted returns obtained from investments. The experiment shows that, in a synergistic relational context when the buyer maintains bargaining power, the investment shifts of the buyer and the supplier accord well with theoretical predictions. In an adversarial relational context, the results of the experimental study do not correspond well with that predicted by the theoretical model. The implications of the results are discussed and directions for future research are presented.