bluuebunny/crossref_metadata_2025 huggingface dataset:
Superhalogen properties of CumCln clusters: Theory and experiment
Authors: Ko Y. J. , Wang H. , Pradhan K. , Koirala P. , Kandalam A. K. , Bowen K. H. , Jena P.
Published: January 2012

Using a combination of density functional theory and anion photoelectron spectroscopy experiment, we have studied the structure and electronic properties of CuCln− (n = 1–5) and Cu2Cln− (n = 2–5) clusters. Prominent peaks in the mass spectrum of these clusters occurring at n = 2, 3, and 4 in CuCln− and at n = 3, 4, and 5 in Cu2Cln− are shown to be associated with the large electron affinities of their neutral clusters that far exceed the value of Cl. While CuCln (n ≥ 2) clusters are conventional superhalogens with a metal atom at the core surrounded by halogen atoms, Cu2Cln (n ≥ 3) clusters are also superhalogens but with (CuCl)2 forming the core. The good agreement between our calculated and measured electron affinities and vertical detachment energies confirm not only the calculated geometries of these superhalogens but also our interpretation of their electronic structure and relative stability.
Dipolar interactions in magnetic nanowire aggregates
Authors: Maurer Thomas , Zighem Fatih , Fang Weiqing , Ott Frédéric , Chaboussant Grégory , Soumare Yaghoub , Atmane Kahina Ait , Piquemal Jean-Yves , Viau Guillaume
Published: January 2012

We investigate the effect of dipolar interactions on the magnetic properties of nanowire aggregates. Micromagnetic simulations show that dipolar interactions between wires are not detrimental to the high coercivity properties of magnetic nanowires, even in very dense aggregates. This is confirmed by experimental magnetization measurements and Henkel plots, which show that the dipolar interactions are small. Indeed, we show that misalignment of the nanowires in aggregates leads to a coercivity reduction of only 30%. Direct dipolar interactions between nanowires, even as close as 2 nm, have small effects (maximum coercivity reduction of ∼15%) and are very sensitive to the detailed geometrical arrangement of the wires. These results strengthen the potential of elongated single domain particles for applications requiring high coercivity properties.
Magnetoelectric effect and the upper critical field in superconductors without inversion center
Authors: Mineev V. P.
Published: January 2012

Solving the Ginzburg–Landau equation we demonstrate that the paramagnetic limiting of superconducting state in the superconductors without space inversion symmetry is significantly weakened. It is caused by so called magnetoelectric mechanism proving to be effective or not depending of the magnetic field direction and the crystal symmetry.
Local and global superconductivity in bismuth
Authors: Baring Luis A. , da Silva Robson R. , Kopelevich Yakov
Published: January 2012

We performed magnetization M(H, T) and magnetoresistance R(T, H) measurements on powdered (grain size ∼149 μm) as well as highly oriented rhombohedral (A7) bismuth (Bi) samples consisting of single crystalline blocks of size ∼1 × 1 mm in the plane perpendicular to the trigonal c axis. The obtained results revealed the occurrence of (1) local superconductivity in powdered samples with Tc(0) = (8.75 ± 0.05) K, and (2) global superconductivity at Tc(0) = (7.3 ± 0.1) K in polycrystalline Bi triggered by low-resistance ohmic contacts with silver (Ag) normal metal. The results provide evidence that the superconductivity in Bi is localized in a tiny volume fraction, probably at intergrain or Ag/Bi interfaces. On the other hand, the occurrence of global superconductivity observed for polycrystalline Bi can be accounted for by enhancement of the superconducting order parameter phase stiffness induced by the normal metal contacts, the scenario proposed in the context of “pseudogap regime” in cuprates [E. Berg et al., Phys. Rev. B 78, 094509 (2008)].
Relativistic and nonrelativistic bound states of the isotonic oscillator by Nikiforov-Uvarov method
Authors: Ikhdair Sameer M. , Sever Ramazan
Published: January 2012

A nonpolynomial one-dimensional quantum potential in the form of an isotonic oscillator (harmonic oscillator with a centripetal barrier) is studied. We provide the nonrelativistic bound state energy spectrum En and the wave functions ψn(x) in terms of the associated Laguerre polynomials in the framework of the Nikiforov-Uvarov method. Under the spin and pseudospin symmetric limits, the analytic eigenvalues and the corresponding two-component upper- and lower-spinors of the Dirac particle are obtained in closed form.
Dipolophoresis of interacting conducting nano-particles of finite electric double layer thickness
Authors: Miloh Touvia
Published: January 2012

A general integral method is presented for calculating the dipolophoretic velocities of two interacting, ideally polarizable colloids of arbitrary electric double layer thickness under weak AC electric forcing. The 12 non-linear mobilities are comprised of induced-charge-electrophoresis (ICEP), dielectrophoresis (DEP), and Faxén-Stokes contributions. The explicit integral scheme, based on the Teubner [J. Chem. Phys. 76, 5564 (1982)] formulation, is demonstrated for the case of two-sphere interaction. Further simplifications using the remote-sphere approximation are employed and the asymptotic results thus obtained are compared against those recently obtained by Saintillan [Phys. Fluids 20, 067104 (2008)] and extend the latter for finite Debye scales and forcing frequencies. It is also shown that the same methodology can be used to determine the mobility of a polarized particle in the proximity of an insulating or conducting plane boundary. The case of a spherical colloid near an uncharged insulating planar wall is of special interest and by using the Lorentz image solution, we readily recover the large-spacing approximation of Yariv [Proc. R. Soc. A. London Ser. A 465, 709 (2009)] as a limiting case.
Measurements of axial instability waves in the near exit region of a high speed liquid jet
Authors: Portillo J. E. , Collicott S. H. , Blaisdell G. A.
Published: January 2012

This work presents wavelength measurements of axial instability waves along the surface of a liquid jet operated within the atomization regime. The surface waves appear in the near exit region of the initially laminar jet. The measurements show that the waves stretch as they are convected downstream before the flow becomes turbulent. A set of experiments using three different cylindrical nozzles of length-to-diameter ratios of one, five and ten are performed at jet velocities ranging between 10 and 40 m/s. These sets of tests allow variations in flow Reynolds number, based on the momentum thickness at the exit of the nozzle, between 150 and 750. The measurements provide statistically validated wavelength measurements as a function of the axial coordinate. These measurements are then compared with three stability models and are found to support the hypothesis that the most important mechanism responsible for the presence of the instability waves is a pocket of absolute instability present near the exit of the nozzle. This pocket is responsible for amplifying disturbances of a given frequency as well as feeding them upstream into the flow.
Experimental study of flight effects on screech in underexpanded jets
Authors: André Benoît , Castelain Thomas , Bailly Christophe
Published: January 2012

Flight effects on screech from an underexpanded supersonic jet have been experimentally investigated in a free jet facility. Screech frequency prediction is addressed, and some conclusions about the convection velocity under flight conditions are drawn. An azimuthal near field acoustic antenna is used to investigate the modal behaviour of screech with forward flight effects. Several mode switchings are identified as the flight velocity is increased but none can be related to a change in the screech azimuthal mode content. Screech is enhanced by flight at high fully expanded Mach number Mj. This conclusion, established from acoustic far field measurements, is supported by the analysis of schlieren visualizations.
Interactions between turbulence and flames in premixed reacting flows
Authors: Hamlington Peter E. , Poludnenko Alexei Y. , Oran Elaine S.
Published: January 2012

The interactions between turbulence and flames in premixed reacting flows are studied for a broad range of turbulence intensities by analyzing scalar (reactant mass-fraction) gradient, vorticity, and strain rate fields. The analysis is based on fully compressible, three-dimensional numerical simulations of H2-air combustion in an unconfined domain. For low turbulence intensities, a flame reconstruction method based on the scalar gradient shows that the internal flame structure is similar to that of a laminar flame, while the magnitudes of the vorticity and strain rate are suppressed by heat release and there is substantial anisotropy in the orientation of intense vortical structures. As the turbulence intensity increases, the local flame orientation becomes increasingly isotropic, and the flame preheat zone is substantially broadened. There is, however, relatively little broadening of the reaction zone, even for high intensities. At high turbulence intensities, the vorticity and strain rate are only weakly affected by the flame, and their interactions with the scalar gradient are similar to those found in nonreacting turbulence. A decomposition of the total strain rate into components due to turbulence and the flame shows that vorticity suppression depends on the relative alignment between vorticity and the flame surface normal. This effect is used to explain the anisotropy of intense vortices at low intensities. The decomposition also reveals the separate effects of turbulent and dilatational straining on the flame width.
Epitaxial Ag wires with a single grain boundary for electromigration
Authors: Sindermann S. , Witt C. , Spoddig D. , Hoegen M. Horn-von , Dumpich G. , Heringdorf F.-J. Meyer zu
Published: January 2012

Test structures for electromigration with defined grain boundary configurations can be fabricated using focused ion beam (FIB). We present a novel approach of combining epitaxial growth of Ag islands with FIB milling. Depending on the growth parameters, bi-crystalline Ag islands can be grown on Si(111) surfaces and can be structured into wires by FIB. To avoid doping effects of the used Ga FIB, silicon on insulator (SOI) substrates are used. By cutting through the device layer of the SOI substrate with deep trenches, the Ag wire can be electrically separated from the rest of the substrate. In this way, Ag wires with one isolated grain boundary of arbitrary direction can be assembled. Using scanning electron microscopy we demonstrate the feasibility of our approach.
The magnetic structure of a thin ferromagnetic film on the rough surface of an antiferromagnet
Authors: Kovalev A. S. , Pankratova M. L.
Published: January 2012

The magnetic structure (including domanization) of a thin ferromagnetic film in contact with a rigid antiferromagnet is investigated under the assumption that the interface is rough and contains individual atomic steps of different signs, isolated “dipole of the steps,” and a space-ordered periodic system of steps of alternate signs.
Vibrationally averaged post Born-Oppenheimer isotopic dipole moment calculations approaching spectroscopic accuracy
Authors: Arapiraca A. F. C. , Jonsson Dan , Mohallem J. R.
Published: January 2012

We report an upgrade of the Dalton code to include post Born-Oppenheimer nuclear mass corrections in the calculations of (ro-)vibrational averages of molecular properties. These corrections are necessary to achieve an accuracy of 10−4 debye in the calculations of isotopic dipole moments. Calculations on the self-consistent field level present this accuracy, while numerical instabilities compromise correlated calculations. Applications to HD, ethane, and ethylene isotopologues are implemented, all of them approaching the experimental values.
Efficient electron dynamics with the planewave-based real-time time-dependent density functional theory: Absorption spectra, vibronic electronic spectra, and coupled electron-nucleus dynamics
Authors: Min Seung Kyu , Cho Yeonchoo , Kim Kwang S.
Published: January 2012

The electron dynamics with complex third-order Suzuki-Trotter propagator (ST3) has been implemented into a planewave (PW) based density functional theory program, and several applications including linear absorption spectra and coupled electron-nucleus dynamics have been calculated. Since the ST3 reduces the number of Fourier transforms to less than half compared to the fourth-order Suzuki-Trotter propagator (ST4), more than twice faster calculations are possible by exploiting the ST3. We analyzed numerical errors of both the ST3 and the ST4 in the presence/absence of an external field for several molecules such as Al2, N2, and C2H4. We obtained that the ST3 gives the same order of numerical errors (10−5 Ry after 100 fs) as the ST4. Also, the time evolution of dipole moments, hence the absorption spectrum, is equivalent for both ST3 and ST4. As applications, the linear absorption spectrum for an ethylene molecule was studied. From the density difference analysis, we showed that the absorption peaks at 6.10 eV and 7.65 eV correspond to the π → 4ag and π → π* excitation bands, respectively. We also investigated the molecular vibrational effect to the absorption spectra of an ethylene molecule and the dynamics of a hydrogen molecule after the σ → σ* transition by formulating coupled electron-nucleus dynamics within the Ehrenfest regime. The trajectory of nuclei follows the excited state potential energy curve exactly.
Gyrokinetic determination of the electrostatic potential of rotating magnetic islands in tokamaks
Authors: Siccinio M. , Poli E. , Casson F. J. , Hornsby W. A. , Peeters A. G.
Published: January 2012

The electrostatic potential related to a magnetic island structure with imposed width and rotation frequency is studied by means of gyrokinetic simulations, which allow its self-consistent determination via the Poisson equation. An adiabatic response of the trapped ions at the island separatrix leads to a significant smoothing of the potential with respect to analytic calculations based on a complete flattening of the pressure profile inside the island. As a consequence, the magnitude of the polarization current is drastically reduced. When the island size is comparable to the ion banana width, the adiabatic response covers the whole island region, leading to a reduced density flattening for islands rotating in the electron diamagnetic direction. This confirms previous results based on drift-kinetic simulations.
Prepotential approach to solvable rational extensions of Harmonic Oscillator and Morse potentials
Authors: Ho C.-L.
Published: January 2012

We show how the recently discovered solvable rational extensions of Harmonic Oscillator and Morse potentials can be constructed in a direct and systematic way, without the need of supersymmetry, shape invariance, Darboux-Crum, and Darboux-Bäcklund transformations.
Surface and electronic structure of 6H-SiC(0001)-(3 × 3) surfaces and ultrathin Ag films on Si(111) and Si(001)
Authors: Gasparov V. A.
Published: January 2012

Surface topographic (LEED, STM) and spectroscopic (ARUPS, XPS, STS) studies have been performed on Si-terminated 6H-SiC(0001)-(3 × 3) surfaces and Ag superstructures and ultrathin films on Si(001) and Si(111) surfaces, using a scanning tunneling microscope (STM) in ultrahigh vacuum. Our results confirm that 2D epitaxial metal growth is favored on Si(001) at low temperatures and a solid, two-domain Ag(111) film has been achieved at coverages as low as 10 ML. The films reveal a morphology with 3-dimensional features and with a well defined honeycomb structure in between. An atomically flat Si(111)/Ag-(3×3)R30∘ surface has been modified by use of a scanning tunneling microscope (STM) in ultrahigh vacuum (UHV). High quality 6H-SiC(0001)-(3 × 3) and Si(111)/-Ag(3×3)R30∘ upper structures have been prepared and studied by means of ARUPS, XPS and LEED. The local density of states proportional to the spectrum of normalized differential conductivity (dI/dV)/(I/V) vs V reveals distinct bands of empty (−0.6 eV) and filled (0.65 eV) sites separated by 1.2 eV, for both areas. The results support the use of a Mott-Hubbard-type model for calculating the density of states of 6H-SiC(0001)-(3 × 3) surfaces with a Hubbard gap of 1 eV.
On a relationship between molecular polarizability and partial molar volume in water
Authors: Ratkova Ekaterina L. , Fedorov Maxim V.
Published: January 2012

We reveal a universal relationship between molecular polarizability (a single-molecule property) and partial molar volume in water that is an ensemble property characterizing solute-solvent systems. Since both of these quantities are of the key importance to describe solvation behavior of dissolved molecular species in aqueous solutions, the obtained relationship should have a high impact in chemistry, pharmaceutical, and life sciences as well as in environments. We demonstrated that the obtained relationship between the partial molar volume in water and the molecular polarizability has in general a non-homogeneous character. We performed a detailed analysis of this relationship on a set of ∼200 organic molecules from various chemical classes and revealed its fine well-organized structure. We found that this structure strongly depends on the chemical nature of the solutes and can be rationalized in terms of specific solute-solvent interactions. Efficiency and universality of the proposed approach was demonstrated on an external test set containing several dozens of polyfunctional and druglike molecules.
Invariant algebraic surfaces for the reduced three-wave interaction system
Authors: Mahdi Adam , Valls Claudia
Published: January 2012

In this paper, we consider the three-wave interaction system \documentclass[12pt]{minimal}\begin{document}$\dot{x}=\gamma x +\delta y +z\break -2 y^2, \quad \dot{y} =\gamma y -\delta x +2 x y, \quad \dot{z} =-2 z -2 z x,$\end{document}ẋ=γx+δy+z−2y2,ẏ=γy−δx+2xy,ż=−2z−2zx, where γ, δ are real parameters. Our main results are the complete characterization of all values of the parameters γ, δ for which the three-wave interaction system admits either invariant algebraic surfaces or algebraic (polynomial or rational) first integrals.
Quantitative strain mapping of InAs/InP quantum dots with 1 nm spatial resolution using dark field electron holography
Authors: Cooper David , Rouviere Jean-Luc , Béché Armand , Kadkhodazadeh Shima , Semenova Elizaveta S. , Yvind Kresten , Dunin-Borkowski Rafal
Published: January 2012

The optical properties of semiconductor quantum dots are greatly influenced by their strain state. Dark field electron holography has been used to measure the strain in InAs quantum dots grown in InP with a spatial resolution of 1 nm. A strain value of 5.4% ± 0.1% has been determined which is consistent with both measurements made by geometrical phase analysis of high angle annular dark field scanning transmission electron microscopy images and with simulations.
Spin-transfer mechanism for magnon-drag thermopower
Authors: Lucassen M. E. , Wong C. H. , Duine R. A. , Tserkovnyak Y.
Published: January 2012

We point out a relation between the dissipative spin-transfer-torque parameter β and the contribution of magnon drag to the thermoelectric power in conducting ferromagnets. Using this result, we estimate β in iron at low temperatures, where magnon drag is believed to be the dominant contribution to the thermopower. Our results may be used to determine β from magnon-drag-thermopower experiments, or, conversely, to infer the strength of magnon drag via experiments on spin transfer.
Interplay of index contrast with periodicity in polymer photonic crystals
Authors: Finlayson Chris E. , Haines Andrew I. , Snoswell David R. E. , Kontogeorgos Andreas , Vignolini Silvia , Baumberg Jeremy J. , Spahn Peter , Peter Hellmann G.
Published: January 2012

We report how the strength of resonant Bragg reflection from polymeric photonic crystals (polymer opals) varies linearly with the refractive-index contrast, Δn, in contrast to the quadratic buildup of Fresnel reflections scaling as (Δn)2. This occurs due to the interplay of disorder and periodicity, in agreement with a simple 1-dimensional periodic model. Goniometry experiments show that opal films exhibit “cones” of resonantly scattered light, which extend to ±20° angular deviation from the specular direction. The intensity of the scattering cones varies super-linearly with Δn. Such medium contrast photonic crystals are of significant interest for understanding structural colors exhibited in nature, by structures with inherent disorder.
Contributions to anelasticity in langasite and langatate
Authors: Johnson Ward L. , Kim Sudook A. , Uda Satoshi , Rivenbark Christine F.
Published: January 2012

Maximization of the quality factors Q of langasite (LGS) and langatate (LGT) is necessary for optimal performance of acoustic resonators of these materials in frequency-control and high-temperature sensing applications. In this report, measurements and least-squares analysis of Q−1 as a function of ultrasonic frequency and temperature of undoped LGS (100 K to 750 K) and LGT (300 K to 760 K) reveal a superposition of physical effects, including point-defect relaxations and intrinsic phonon-phonon loss. In LGS, these effects are superimposed on a large temperature-dependent background with weak frequency dependence that is interpreted as arising from a relaxation process with a distribution of activation energies. This distributed relaxation is suggested to be a result of anelastic kink migration. No evidence for a significant background of this form is found in the LGT specimen, consistent with the lower measured dislocation etch-pit density of this crystal. The analysis of the dependence of Q−1 of LGT on frequency and temperature indicates that, at near-ambient temperatures, the damping in this specimen is close to the intrinsic limit determined by phonon-phonon interactions. Piezoelectric/carrier relaxation, which must occur at sufficiently elevated temperatures, is found not to be a significant contribution to Q−1, relative to defect-related contributions, in either LGS or LGT in the measured range of temperatures.
Uncompensated antiferromagnetic moments in Mn-Ir/FM (FM = Ni-Co, Co-Fe, Fe-Ni) bilayers: Compositional dependence and its origin
Authors: Takahashi Hirokazu , Kota Yohei , Tsunoda Masakiyo , Nakamura Tetsuya , Kodama Kenji , Sakuma Akimasa , Takahashi Migaku
Published: January 2012

Ferromagnetic (FM) material dependence of the uncompensated (UC) antiferromagnetic (AF) moments in AF/FM exchange biased bilayers has been studied using the x-ray magnetic circular dichroism technique in the AF/FM (AF = γ-Mn-Ir, FM = Ni-Co, Co-Fe, Fe-Ni) bilayers. The direction and magnitude of the UC-Mn moment change significantly when the composition of the FM layer changes. The crystal structure of the FM layer affects the magnitude of the UC-Mn moments. The UC-Mn moments and the FM moments of Fe-rich alloys prefer the anti-parallel alignment. Conversely, the UC-Mn moments align parallel to the FM moments in Co-rich or Ni-rich regions. A first-principles calculation pertaining to the L12-Mn3Ir/FM (FM = Ni4-nCon, Co4-nFen, Fe4-nNin; n = 0, 1, 2, 3) bilayer system was carried out to characterize the UC-Mn moments near the interface. It was found that the UC-Mn moments originate from the reorientation of the magnetic moments of Mn and other ferromagnetic atoms near the AF/FM interface. The calculated result for the compositional dependence of the UC-Mn moment is in good agreement with the obtained experimental data. As a result, the dependence of the UC-Mn moment on the composition of the FM layer can be explained qualitatively based on the model that the band filling fraction modifies the direction and the magnitude of exchange coupling between AF and FM atoms, depending on the crystal structure and the composition of the FM layer.
Nonlinear oscillations and waves in an arbitrary mass ratio cold plasma
Authors: Verma Prabal Singh
Published: January 2012

It is well known that nonlinear standing oscillations in an arbitrary mass ratio cold plasma always phase mix away. However, there exist nonlinear electron-ion traveling wave solutions, which do not exhibit phase mixing because they have zero ponderomotive force. The existence of these waves has been demonstrated using a perturbation method. Moreover, it is shown that cold plasma BGK waves [Albritton et al., Nucl. Fusion 15, 1199 (1975)] phase mix away if ions are allowed to move and the scaling of phase mixing is found to be different from earlier work [Sengupta et al., Phys. Rev. Lett. 82, 1867 (1999)]. Phase mixing of these waves has been further verified in 1-D particle in cell simulation.
Thermal dependence of the optical gain and threshold current density of GaInNAs/GaAs/AlGaAs quantum well lasers
Authors: Wu Shudong , Wan Li
Published: January 2012

The thermal dependence of the optical gain and threshold current density of GaInNAs/GaAs/AlGaAs quantum well (QW) lasers with the emission wavelength of 1.3 μm have been theoretically investigated. The optical gain is found to decrease with the increase of the temperature due to the hole leakage in the separate confinement heterostructure (SCH) region. The distribution of unconfined electrons in the SCH region is negligible while the distribution of unconfined holes in the SCH region plays an important role in the leakage process, reflecting the smaller bandgap discontinuity in the valence band than in the conduction band. The threshold current density increases with the increase of temperature, which is dominated by the monomolecular recombination process. Our calculated threshold current densities with temperatures are in agreement with the available experimental results.
Low field anisotropic colossal magnetoresistance in Sm0.53Sr0.47MnO3 thin films
Authors: Srivastava Manoj K. , Singh M. P. , Kaur Amarjeet , Razavi F. S. , Singh H. K.
Published: January 2012

Sm0.53Sr0.47MnO3 (SSMO) thin films (thicknesses ∼200 nm) were deposited by on-axis dc magnetron sputtering on the single crystal LSAT (001) substrates. These films are oriented along the out of plane c-direction. The ferromagnetic and insulator-metal transition occurs at TC ∼ 96 and TIM ∼ 91 K, respectively. The magnetization easy axis is observed to lie in the plane of the film while the magnetic hard axis is found to be along the normal to this. The magnetotransport of the SSMO films, which was measured as a function of angle (θ) between the magnetic field (H) and plane of the film, shows colossal anisotropy. Magnetoresistance (MR) decreases drastically as θ increases from 0° (H//easy axis) to 90° (H//hard axis). The out-of-plane anisotropic MR is as high as 88% at H = 3.6 kOe and 78 K. The colossal anisotropy has been explained in terms of the magnetic anisotropies at play and the magnetic domain motion in applied magnetic field.
Thermomagnetic conversion efficiencies for ferromagnetic materials
Authors: Hsu Chin-Jui , Sandoval Samuel M. , Wetzlar Kyle P. , Carman Gregory P.
Published: January 2012

The theory of thermomagnetic generation is reviewed and an efficiency analysis using experimentally measured magneto-thermal properties of 3d transitional and 4f rare earth ferromagnetic elements is presented in this study. While theoretical results suggest that 55% of Carnot efficiency is possible, experimental data indicate values smaller than 25% of Carnot efficiency unless large magnetic field (e.g., Ha ∼ 80 kOe) is applied. For smaller magnetic fields representative of NdFeB permanent magnets (e.g., Ha = 3 kOe), the largest efficiencies are obtained for operating ferromagnetic materials over a smaller temperature difference (ΔT = 5 K). Furthermore, single crystal materials are found to have superior efficiencies, as do elements that undergo an order-to-order phase transition. Both of these later results relate to increased magnetization changes over a given ΔT. These results are subsequently used to postulate that a single domain structure will produce larger efficiencies due to the higher magnetization present over a wide range of magnetic fields when compared to multi-domain materials. Calculations for a Gd single domain suggest efficiencies on the order of 30% are possible, representing a threefold increase from multi-domain Gd at relatively small magnetic fields.
Influence of silicon on the thermally-induced crystallization process of Si-Sb4Te phase change materials
Authors: Cheng Yan , Song Zhitang , Gu Yifeng , Song Sannian , Rao Feng , Wu Liangcai , Liu Bo , Feng Songlin
Published: January 2012

Si-Sb4Te phase change thin films with different silicon contents have been investigated by in situ heating technique in transmission electron microscopy (TEM). The studies show that Si-doping can significantly improve the thermal stability of Si-Sb4Te thin films, refine their grain size, and change the nucleation characters with the increase of silicon content. By in situ annealing in TEM, the crystalline phase of Si-Sb4Te thin films can be indexed as hexagonal Sb structure, and Si is still holding amorphous state which is considered as the reason for the change, by destroying the long-range order lattice of crystal grains.
More evidence of the crucial roles of surface superhydrophobicity in free and safe maneuver of water strider
Authors: Su Yewang , He Shijie , Ji Baohua , Huang Yonggang , Hwang Keh-Chih
Published: January 2012

This letter presents a study of the effect of surface superhydrophobicity on piercing force and detaching force of water strider’s leg when it vertically contact with water surface. We showed that in contrast to the parallel contact of the leg with water at which the piercing force is insensitive to the contact angle which raised much debate on the functions of superhydrophobicity of water strider’s leg, the piercing force of the vertical contact is, however, very sensitive to the contact angle, which then suggests the surface superhydrophobicity is indeed crucial for water strider’s free and safe activities on water surface.
Whispering gallery modes with different polarizations in semiconductor microrod with rectangle shape
Authors: Ye Xiaoliang , Mao Huibing , Wang Jiqing , Zhu Ziqiang
Published: January 2012

The whispering gallery modes (WGMs) of the ZnO photoluminescence emission were investigated in this paper. The transmission electron microscopy and X-ray diffraction results confirm that the rectangle microrod has a single crystalline wurtzite structure. Except for the band-edge emission, the visible luminescence band of the ZnO microrod presents the WGMs with two different polarizations. In a large waveband, the WGMs modes with two different polarizations have same mode spacing. Because of the phase difference in reflectance for two polarizations, the WGMs for s and p polarizations are distributed interlacedly. Due to the property difference, the WGMs for two polarizations have different appearances.
An activated scheme for resonance energy transfer in conjugated materials
Authors: Köse Muhammet E.
Published: January 2012

Energy transfer mechanism in conjugated materials has been demonstrated with an activated expression, which is equivalent to Fermi's golden rule. Spectral overlap integrals obtained from simulated spectra of model chromophores agree very well with the results obtained with the activated formula. Although this approach works best for chromophores with spectral profiles resembling a Gaussian distribution, the activated expression formula also performs quite well for chromophores with vibronically resolved spectra. Activation energies for exciton hopping can also be predicted using a phonon coupled exciton relaxation scheme. The accuracy of predictions with this new approach is quite attractive and hence should allow practical applications.
The allometric relationship between mean fibre diameter of mohair and the fleece-free liveweight of Angora goats over their lifetime
Authors: McGregor B. A. , Butler K. L. , Ferguson M. B.
Published: January 2012

As mean fibre diameter (MFD) is the primary determinant of mohair price we aimed to quantify the lifetime changes in mohair MFD as Angora goats aged and grew. Measurements were made over 12 shearing periods on a population of Angora goats representing the current range and diversity of genetic origins including South African, Texan and interbred admixtures of these and Australian sources. Records of sire, dam, birthweight, birth parity, liveweight, fleece growth and fleece quality were taken for does and castrated males (wethers) (n = 267 animals). Fleece-free liveweights (FFLwt) were determined for each goat at shearing time by subtracting the greasy fleece weight from the liveweight recorded immediately before shearing. A restricted maximum likelihood growth curve model was developed for relating MFD to FFLwt, age and other measurements. A simple way of describing the results is: MFD = κ (FFLwt)β E; where κ is a parameter that can vary in a systematic way with shearing(age), breed, weaning weight, sire, dam and individual; β is a parameter that is the same for nearly the whole study; and E are independent errors from a log-normal distribution. The analysis shows that = 0.34, with s.e. () = 0.021. Thus, mohair MFD was allometrically related to the cube root of FFLwt over the lifetime of Angora goats. However, the allometric proportionality constant differed in a systematic way with age at shearing, genetic strain, weaning weight, sire, dam and individual. For Texan-breed goats, MFD decreased as weaning weight increased (P = 0.00016). The findings indicate that management factors that affect liveweight and weaning weight have lifetime effects on mohair fibre diameter and therefore the value of mohair and the profitability of the mohair enterprise.
2D–1D Wavelet Reconstruction as a Tool for Source Finding in Spectroscopic Imaging Surveys
Authors: Flöer L. , Winkel B.
Published: January 2012

Today, image denoising by thresholding of wavelet coefficients is a commonly used tool for 2D image enhancement. Since the data product of spectroscopic imaging surveys has two spatial dimensions and one spectral dimension, the techniques for denoising have to be adapted to this change in dimensionality. In this paper we will review the basic method of denoising data by thresholding wavelet coefficients and implement a 2D–1D wavelet decomposition to obtain an efficient way of denoising spectroscopic data cubes. We conduct different simulations to evaluate the usefulness of the algorithm as part of a source finding pipeline.
The Characterised Noise Hi Source Finder: Detecting Hi Galaxies Using a Novel Implementation of Matched Filtering
Authors: Jurek R.
Published: January 2012

The spectral line datacubes obtained from the Square Kilometre Array (SKA) and its precursors, such as the Australian SKA Pathfinder (ASKAP), will be sufficiently large to necessitate automated detection and parametrisation of sources. Matched filtering is widely acknowledged as the best possible method for the automated detection of sources. This paper presents the Characterised Noise Hi (cnhi) source finder, which employs a novel implementation of matched filtering. This implementation is optimised for the 3-D nature of the Hi spectral line observations of the planned Wide-field ASKAP Legacy L-band All-sky Blind surveY (WALLABY). The CNHI source finder also employs a novel sparse representation of 3-D objects, with a high compression rate, to implement the Lutz one-pass algorithm on datacubes that are too large to process in a single pass. WALLABY will use ASKAP's phenomenal 30 square degree field of view to image ∼70% of the sky. It is expected that WALLABY will find 500 000 Hi galaxies out to z ∼0.2.
Genotypic diversity in sorghum inbred lines for grain-filling patterns and other related agronomic traits
Authors: Gambín Brenda L. , Borrás Lucas
Published: January 2012

Opportunities for genetic improvement on specific traits require information on available diversity, together with knowledge on heritability estimates and possible trade-off relations among traits. Sixty-five sorghum inbred lines were evaluated for grain filling and other agronomic traits during 2008 and 29 re-evaluated in 2009. Time to anthesis, final grain weight (GW), grain growth rate, duration of grain filling, maximum water content, grain desiccation rate, moisture concentration at physiological maturity, plant height, panicle length, grain number per plant and final yield per plant were measured both years. Results highlighted the available variability for grain-filling patterns in sorghum, and genotypic differences (P < 0.05) for all traits were evident. Final GW variation (16–44 mg grain–1 in 2008, and 20–40 mg grain–1 in 2009) was achieved through different combinations of rate (3.27–9.78 mg degree-days grain–1 10−2) and duration of grain filling (413–853 degree-days). Calculated heritability for grain-filling traits ranged from 0.43 to 0.95, showing GW and maximum water content had the highest values. Grain number showed consistent negative associations with grain growth rate but not with GW due to grain-filling duration variability. This suggests selecting longer grain filling can increase GW (and yield) without negative trade-off relations with grain number.
The influence of prescribed fire on the extent of wildfire in savanna landscapes of western Arnhem Land, Australia
Authors: Price Owen F. , Russell-Smith Jeremy , Watt Felicity
Published: January 2012

Fire regimes in many north Australian savanna regions are today characterised by frequent wildfires occurring in the latter part of the 7-month dry season. A fire management program instigated from 2005 over 24 000 km2 of biodiversity-rich Western Arnhem Land aims to reduce the area and severity of late dry-season fires, and associated greenhouse gas emissions, through targeted early dry-season prescribed burning. This study used fire history mapping derived mostly from Landsat imagery over the period 1990–2009 and statistical modelling to quantify the mitigation of late dry-season wildfire through prescribed burning. From 2005, there has been a reduction in mean annual total proportion burnt (from 38 to 30%), and particularly of late dry-season fires (from 29 to 12.5%). The slope of the relationship between the proportion of early-season prescribed fire and subsequent late dry-season wildfire was ~–1. This means that imposing prescribed early dry-season burning can substantially reduce late dry-season fire area, by direct one-to-one replacement. There is some evidence that the spatially strategic program has achieved even better mitigation than this. The observed reduction in late dry-season fire without concomitant increase in overall area burnt has important ecological and greenhouse gas emissions implications. This efficient mitigation of wildfire contrasts markedly with observations reported from temperate fire-prone forested systems.
PAI-1–regulated miR-21 defines a novel age-associated fibrogenic pathway in muscular dystrophy
Authors: Ardite Esther , Perdiguero Eusebio , Vidal Berta , Gutarra Susana , Serrano Antonio L. , Muñoz-Cánoves Pura
Published: January 2012

Disruption of skeletal muscle homeostasis by substitution with fibrotic tissue constitutes the principal cause of death in Duchenne muscular dystrophy (DMD) patients, yet the implicated fibrogenic mechanisms remain poorly understood. This study identifies the extracellular PAI-1/urokinase-type plasminogen activator (uPA) balance as an important regulator of microribonucleic acid (miR)–21 biogenesis, controlling age-associated muscle fibrosis and dystrophy progression. Genetic loss of PAI-1 in mdx dystrophic mice anticipated muscle fibrosis through these sequential mechanisms: the alteration of collagen metabolism by uPA-mediated proteolytic processing of transforming growth factor (TGF)–β in muscle fibroblasts and the activation of miR-21 expression, which inhibited phosphatase and tensin homologue and enhanced AKT signaling, thus endowing TGF-β with a remarkable cell proliferation–promoting potential. Age-associated fibrogenesis and muscle deterioration in mdx mice, as well as exacerbated dystrophy in young PAI-1−/− mdx mice, could be reversed by miR-21 or uPA-selective interference, whereas forced miR-21 overexpression aggravated disease severity. The PAI-1–miR-21 fibrogenic axis also appeared dysregulated in muscle of DMD patients, providing a basis for effectively targeting fibrosis and muscular dystrophies in currently untreatable individuals.
Ubiquitylation of the nuclear pore complex controls nuclear migration during mitosis in S. cerevisiae
Authors: Hayakawa Akira , Babour Anna , Sengmanivong Lucie , Dargemont Catherine
Published: January 2012

Nuclear pore complexes (NPCs) correspond to large protein transport complexes responsible for selective nucleocytoplasmic exchange. Although research has revealed much about the molecular architecture and roles of the NPC subcomplexes, little is known about the regulation of NPC functions by posttranslational modifications. We used a systematic approach to show that more than half of NPC proteins were conjugated to ubiquitin. In particular, Nup159, a nucleoporin exclusively located on the cytoplasmic side of the NPC, was monoubiquitylated by the Cdc34/SCF (Skp1–Cdc53–F-box E3 ligase) enzymes. Preventing this modification had no consequences on nuclear transport or NPC organization but strongly affected the ability of Nup159 to target the dynein light chain to the NPC. This led to defects in nuclear segregation at the onset of mitosis. Thus, defining ubiquitylation of the yeast NPC highlights yet-unexplored functions of this essential organelle in cell division.
Demonstration of islet-autoreactive CD8 T cells in insulitic lesions from recent onset and long-term type 1 diabetes patients
Authors: Coppieters Ken T. , Dotta Francesco , Amirian Natalie , Campbell Peter D. , Kay Thomas W.H. , Atkinson Mark A. , Roep Bart O. , von Herrath Matthias G.
Published: January 2012

A direct association of islet-autoreactive T cells with β cell destruction in human pancreatic islets from type 1 diabetes (T1D) patients has never been demonstrated, and little is known about disease progression after diagnosis. Frozen pancreas samples were obtained from 45 cadaveric T1D donors with disease durations ranging from 1 wk to >50 yr, 14 nondiabetic controls, 5 nondiabetics with islet autoantibodies, 2 cases of gestational diabetes, and 6 T2D patients. Sections were systematically analyzed for the presence of insulin-sufficient β cells, CD8+ insulitic lesions, and HLA class I hyperexpression. Finally, consecutive sections from HLA-A2–expressing individuals were probed for CD8 T cell reactivity against six defined islet autoantigens associated with T1D by in situ tetramer staining. Both single and multiple CD8 T cell autoreactivities were detected within individual islets in a subset of patients up to 8 yr after clinical diagnosis. Pathological features such as HLA class I hyperexpression and insulitis were specific for T1D and persisted in a small portion of the patients with longstanding disease. Insulitic lesions consistently presented in a multifocal pattern with varying degrees of infiltration and β cell loss across affected organs. Our observations provide the first direct proof for islet autoreactivity within human islets and underscore the heterogeneous and chronic disease course.
The E3 ubiquitin ligase Mule acts through the ATM–p53 axis to maintain B lymphocyte homeostasis
Authors: Hao Zhenyue , Duncan Gordon S. , Su Yu-Wen , Li Wanda Y. , Silvester Jennifer , Hong Claire , You Han , Brenner Dirk , Gorrini Chiara , Haight Jillian , Wakeham Andrew , You-Ten Annick , McCracken Susan , Elia Andrew , Li Qinxi , Detmar Jacqui , Jurisicova Andrea , Hobeika Elias , Reth Michael , Sheng Yi , Lang Philipp A. , Ohashi Pamela S. , Zhong Qing , Wang Xiaodong , Mak Tak W.
Published: January 2012

Cellular homeostasis is controlled by pathways that balance cell death with survival. Mcl-1 ubiquitin ligase E3 (Mule) is an E3 ubiquitin ligase that targets the proapoptotic molecule p53 for polyubiquitination and degradation. To elucidate the role of Mule in B lymphocyte homeostasis, B cell–specific Mule knockout (BMKO) mice were generated using the Cre–LoxP recombination system. Analysis of BMKO mice showed that Mule was essential for B cell development, proliferation, homeostasis, and humoral immune responses. p53 transactivation was increased by two- to fourfold in Mule-deficient B cells at steady state. Genetic ablation of p53 in BMKO mice restored B cell development, proliferation, and homeostasis. p53 protein was increased in resting Mule-deficient mouse embryonic fibroblasts (MEFs) and embryonic stem (ES) cells. Loss of Mule in both MEFs and B cells at steady state resulted in increased levels of phospho–ataxia telangiectasia mutated (ATM) and the ATM substrate p53. Under genotoxic stress, BMKO B cells were resistant to apoptosis, and control MEFs exhibited evidence of a physical interaction between Mule and phospho-ATM. Phospho-ATM, phospho-p53, and Brca1 levels were reduced in Mule-deficient B cells and MEFs subjected to genotoxic stress. Thus, Mule regulates the ATM–p53 axis to maintain B cell homeostasis under both steady-state and stress conditions.
Classification of fish and non-fish acoustic tracks using discriminant function analysis
Authors: Xie Yunbo , Michielsens Catherine G. J. , Martens Fiona J.
Published: January 2012

Xie, Y., Michielsens, C. G. J., and Martens, F. J. 2012. Classification of fish and non-fish acoustic tracks using discriminant function analysis. – ICES Journal of Marine Science, 69: 313–322. Hydroacoustic data acquired for estimating fish populations contain information on both fish and non-fish targets, so sonar technicians traditionally rely on their knowledge of fish behaviour and experience with hydroacoustics to remove non-fish targets from the hydroacoustic data. This process is often labour-intensive and time-consuming, making real-time assessment of fish populations difficult. Simple solutions are not always available for all circumstances. However, the split-beam sonar data collected in the lower Fraser River, British Columbia, Canada, showed distinct signatures between actively swimming fish and non-fish objects such as drifting debris, surface bubbles, and stationary objects in the water column and off the river bottom. Acoustic tracks of fish and non-fish targets were characterized by differentiable statistical patterns that were amenable to discriminant function analysis (DFA). An application of DFA to segregate fish and non-fish targets detected by a split-beam sonar system in the lower Fraser River is presented, characteristics of user-identified fish and non-fish acoustic tracks being utilized as learning samples for the DFA. Also, a method to rank the discriminating power of individual variables is presented, providing guidance for constructing efficient and effective discriminant functions with variables that offer high discriminating power. The DFA yielded classification accuracies of 96% for fish and 91% for non-fish tracks and reduced the manual sorting time by 50–75%.