bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermodynamic driving force for diffusion: Comparison between theory and simulation
Authors: Whitman Jessica R. , Aranovich Gregory L. , Donohue Marc D.
Published: March 2011

In previous work, lattice density functional theory equations have been recast into differential form to determine a property whose gradient is universally proportional to the diffusive flux. For color counter diffusion, this property appears as the impingement rate onto vacancies and molecules of a species whose density gradient can be influenced by diffusion. Therefore, the impingement rate of a diffusing molecule depends on the mobility of its surroundings. In order to determine the validity of this finding, molecular dynamics simulations of color counter diffusion were performed in which the mobility of the solvent was varied to determine if the flux of the diffusing species responded to the change when all other factors, such as density gradient, available volume, and temperature are held constant.
High frequency resistance of single-walled and multiwalled carbon nanotubes
Authors: Yang Y. , Tan C. Y. , Sun W. Q. , Li W. , Ong C. K. , Liu Y. , Li Y. , Xu S. Y.
Published: March 2011

The electrical resistances of individual single-walled carbon nanotubes (SWCNTs), SWCNT arrays, and multiwalled carbon nanotube (MWCNT) bundles have been measured from frequency of 10 MHz to 16 GHz, using vector network analyzer and ground-source-ground probe on coplanar waveguide (CPW) structured sample stages. Full-wave electromagnetic simulation of the structure has also been performed. Analysis of the experimental and stimulated data indicates that the resistances of individual SWCNTs, SWCNT arrays, and MWCNT bundles are nearly independent of frequency within the frequency range under study. We have also calculated the parasitic capacitance of the CPW open structure, and the results indicate that the parasitic capacitance can greatly influence the high frequency measurement because of high impedance of SWCNT samples.
Molecular beam epitaxial growth of BaTiO3 single crystal on Ge-on-Si(001) substrates
Authors: Merckling C. , Saint-Girons G. , Botella C. , Hollinger G. , Heyns M. , Dekoster J. , Caymax M.
Published: March 2011

Thin films of perovskite type BaTiO3 (BTO) oxide have been grown epitaxially directly on Ge(001) surface at high temperature using molecular beam epitaxy. A stable (2×1) BaGex surface periodicity is the critical enabling template for subsequent BTO heteroepitaxy on Ge(001). Reflection high energy electron diffraction (RHEED) and transmission electron microscopy indicate that high quality heteroepitaxy on Ge-on-Si(001) take place with ⟨100⟩BTO(001)∥⟨110⟩Ge(001) confirming a 45° rotation epitaxial relationship. X-ray diffraction has been used to study the BTO lattice parameters and we evidenced that both tetragonal and cubic phases of BTO are present in the epilayer.
Nonlinear instability of the one-dimensional Vlasov-Yukawa system
Authors: Ha Seung-Yeal , Ha Taeyoung , Hwang Chi-Ok , Lee Ho
Published: March 2011

We discuss the nonlinear instability of some class of stationary solutions to the one-dimensional Vlasov–Yukawa system with a mass parameter m. The Vlasov–Yukawa system corresponds to the short-range correction of the repulsive Vlasov–Poisson system arising from plasma physics. We show that the stationary solutions satisfying the Penrose condition are nonlinearly unstable in small mass regime. In a large mass regime, the massiveness of force carrier particles acts as stabilizer in a finite time interval. We present several numerical results to confirm our analytical results.
In situ spectral calibration method for the impurity influx monitor (divertor) for ITER using angled physical contact fibers
Authors: Iwamae A. , Ogawa H. , Sugie T. , Kusama Y.
Published: March 2011

The in situ calibration method for the impurity influx monitor (divertor) is experimentally examined. The total reflectance of the optical path from the focal point of the Cassegrain telescope to the first mirror is derived using a micro retroreflector array. An optical fiber with angled physical contact (APC) connectors reduces the return edge reflection. APC fibers and a multimode coupler increase the signal-to-noise ratio by about one order compared to that of triple-branched fibers and enable measurement of the wavelength dependence of the total reflectance of the optical system even after potential deterioration of mirror surfaces reduces reflectance.
Intrinsic structure of state space of a quantum system
Authors: Ma Zhi-Hao , Zhu Sen
Published: March 2011

Quantum states play a fundamental role in quantum physics; so it is necessary to study intrinsic structure of quantum states. In this paper, we study topological structure and measurable structure of state space of a quantum system, and find that almost all physical important properties on quantum states coincide.
Darboux-integrable two-component nonlinear hyperbolic systems of equations
Authors: Kostrigina O. S. , Zhiber A. V.
Published: March 2011

An approach based on a study of the structure of characteristic rings is used to solve the classification problem of Darboux-integrable nonlinear hyperbolic systems of equations. We classify two-component systems of equations with two integrals of the first order and two integrals of the second order. For the resulting systems of equations, x − and y − integrals are constructed and their general solutions are found.
Prospect for characterizing interacting soft colloidal structures using spin-echo small angle neutron scattering
Authors: Li Xin , Shew Chwen-Yang , Liu Yun , Pynn Roger , Liu Emily , Herwig Kenneth W. , Smith Gregory S. , Robertson J. Lee , Chen Wei-Ren
Published: March 2011

Spin-echo small angle neutron scattering (SESANS) provides a new experimental tool for structural investigation. Due to the action of spin-echo encoding, SESANS measures a spatial correlation function in real space, as opposed to the structure factor S(Q), I(Q), in momentum (Q) space measured by conventional small angle neutron scattering. To establish the usefulness of SESANS in structural characterization, particularly for interacting colloidal suspensions, we have previously conducted a theoretical study of the SESANS correlation functions for model systems consisting of particles with uniform density profiles [X. Li, C.-Y. Shew, Y. Liu, R. Pynn, E. Liu, K. W. Herwig, G. S. Smith, J. L. Robertson, and W.-R. Chen J. Chem. Phys. 132, 174509 (2010)]. Within the same framework, we explore in the present paper the prospect of using SESANS to investigate the structural characteristics of colloidal systems consisting of particles with nonuniform intraparticle mass distribution. As an example, a Gaussian model of interacting soft colloids is used to investigate the manifestation of structural softness in a SESANS measurement. The exploration shows a characteristically different SESANS correlation function for interacting soft colloids, in comparison to that of a uniform hard sphere system. The difference arises from the Abel transform imbedded in the mathematical formalism bridging the SESANS spectra and the spatial autocorrelation function.
Comprehensive insights into point defect and defect cluster formation in CuInSe2
Authors: Stephan Christiane , Schorr Susan , Tovar Michael , Schock Hans-Werner
Published: March 2011

The concentration of native point defects in CuInSe2 powder material as a function of stoichiometry has been experimentally determined by neutron powder diffraction. A correlation between the Cu/In ratio and the density of VCu as well as InCu has been established and their concentrations are quantified. It is demonstrated, that assuming the spontaneous formation of defect pairs, the density of native point defects is reduced significantly by an order of magnitude. The functionality of a solar device, assuming same conditions like in the analyzed material, may be explained by a neutralization due to the formation of electrically inactive defect complexes.
Ultrafast magnetization relaxation of L1-ordered Fe50Pt50 alloy thin film
Authors: Kim Ji-Wan , Song Hyon-Seok , Jeong Jae-Woo , Lee Kyeong-Dong , Sohn Jeong-Woo , Shima Toshiyuki , Shin Sung-Chul
Published: March 2011

We have investigated the ultrafast magnetization dynamics of L10-ordered Fe50Pt50 thin film by means of a time-resolved magneto-optical Kerr effect measurement. We have found a high Gilbert damping value of α∼0.26, together with a very high precession frequency of f∼85 GHz and the shortest relaxation characteristic time of τ∼6.5 ps ever reported. We believe that L10-ordered FePt film with the unique property of a very high precession frequency and the shortest relaxation time will be very useful for the realization of picosecond spin switching.
Theory of surface segregation in ternary semiconductor quantum dots
Authors: Pandey Sumeet C. , Sfyris Georgios I. , Maroudas Dimitrios
Published: March 2011

We present a phenomenological species transport theory for surface segregation of constituent and dopant atoms in ternary semiconductor quantum dots. The theory employs continuum elasticity to describe species-surface interactions and is used to fit atomistic simulation results according to a first-principles-based force-field parameterization. The theory predicts equilibrium concentration profiles in the form of Maxwellian atmospheres near nanocrystal surfaces. The theory is accurate in the dilute limit and it is validated by fitting results of Monte Carlo simulations of compositional relaxation in InxGa1−xAs and ZnSe1−xTex nanocrystals for various representative sizes (diameters≤5.7 nm) and compositions (x≤0.2).
The effect of electron interactions on the universal properties of systems with optimized off-resonant intrinsic hyperpolarizability
Authors: Watkins David S. , Kuzyk Mark G.
Published: March 2011

Because of the potentially large number of important applications of nonlinear optics, researchers have expended a great deal of effort to optimize the second-order molecular nonlinear-optical response, called the hyperpolarizability. The focus of our present studies is the intrinsic hyperpolarizability, which is a scale-invariant quantity that removes the effects of simple scaling, thus being the relevant quantity for comparing molecules of varying sizes. Past theoretical studies have focused on structural properties that optimize the intrinsic hyperpolarizability, which have characterized the structure of the quantum system based on the potential energy function, placement of nuclei, geometry, and the effects of external electric and magnetic fields. Those previous studies focused on single-electron models under the influence of an average potential. In the present studies, we generalize our calculations to two-electron systems and include electron interactions. As with the single-electron studies, universal properties are found that are common to all systems—be they molecules, nanoparticles, or quantum gases—when the hyperpolarizability is near the fundamental limit.
Single-cycle terahertz pulses with amplitudes exceeding 1 MV/cm generated by optical rectification in LiNbO3
Authors: Hirori H. , Doi A. , Blanchard F. , Tanaka K.
Published: March 2011

Using the tilted-pump-pulse-front scheme, we generate single-cycle terahertz (THz) pulses by optical rectification of femtosecond laser pulses in LiNbO3. In our THz generation setup, the condition that the image of the grating coincides with the tilted-optical-pulse front is fulfilled to obtain optimal THz beam characteristics and pump-to-THz conversion efficiency. By using an uncooled microbolometer-array THz camera, it is found that the THz beam leaving the output face of the LN crystal can be regarded as a collimated rather than point source. The designed focusing geometry enables tight focus of the collimated THz beam with a spot size close to the diffraction limit, and the maximum THz electric field of 1.2 MV/cm is obtained.
Conductive atomic force microscopy studies on dielectric breakdown behavior of ultrathin Al2O3 films
Authors: Ganesan K. , Ilango S. , Mariyappan S. , Baroughi M. Farrokh , Kamruddin M. , Tyagi A. K.
Published: March 2011

Ultrathin films of Al2O3 prepared by atomic layer deposition have been subjected to local electrical stress analysis using conducting atomic force microscopy. The loss of local dielectric integrity through current leakage in these extremely thin films is studied using scanning spreading resistance imaging. Our experimental results shows that repeated voltage stress progressively increases number of leakage spots. While the density of leakage spots increase with higher applied bias for thin oxide films, initial increase and reduction in leakage spots are observed for thick films.
Shape of ferroelectric domains in LiNbO3 and LiTaO3 from defect/domain-wall interactions
Authors: Lee Donghwa , Xu Haixuan , Dierolf Volkmar , Gopalan Venkatraman , Phillpot Simon R.
Published: March 2011

The observed orientations and shapes of ferroelectric domains in stoichiometric and congruent LiTaO3 and LiNbO3 are explained in terms of the differences in the energetics of domain walls, and the energetics of defect/domain-wall interactions. Density functional theory calculations show that the energy of a Y-wall, parallel to (112¯0), is lower than that of the X-walls, parallel to (101¯0), in both stoichiometric LiNbO3 and LiTaO3. As a result the domains are hexagonal and delineated by Y-walls. In congruent LiTaO3, the interaction of antisite defects with domains walls can reverse this order of stability, leading to triangular domains delineated by one type of X-wall. In congruent LiNbO3, the interactions of the antisite defects with the domain walls are too weak to reverse the order of stability of the domains walls; as a result the domains remain hexagonal.
Effects of excluded volume interaction and dimensionality on diffusion-mediated reactions
Authors: Seki Kazuhiko , Wojcik Mariusz , Tachiya M.
Published: March 2011

The kinetic problem of a diffusion-mediated reaction, in which minority reactants are immobile and majority reactants are mobile, is known as the target problem. The standard theory of the target problem ignores the excluded volume interaction between the mobile reactants. Recently, a new theory of the target problem was proposed where the effect of excluded volume interaction was analytically investigated using a lattice model with prohibited double occupancy of the lattice sites. The results of that theory are approximate and need verification. In this work, we perform Monte Carlo simulations on lattices and use their results to assess the accuracy of the analytical theory. We also generalize our theory to the case of different dimensionality and perform calculations for lattices in one- and two-dimensional systems. The analytical results accurately reproduce the simulation results except in the dilute limit in one dimension. For any dimensions, the decay of the target survival probability is accelerated by the presence of excluded volume interaction.
Electrothermal simulation of superconducting nanowire avalanche photodetectors
Authors: Marsili Francesco , Najafi Faraz , Herder Charles , Berggren Karl K.
Published: March 2011

We developed an electrothermal model of NbN superconducting nanowire avalanche photodetectors (SNAPs) on sapphire substrates. SNAPs are single-photon detectors consisting of the parallel connection of N superconducting nanowires. We extrapolated the physical constants of the model from experimental data and we simulated the time evolution of the device resistance, temperature and current by solving two coupled electrical and thermal differential equations describing the nanowires. The predictions of the model were in good quantitative agreement with the experimental results.
Impact of static and dynamic stress on threshold voltage instability in high-k/metal gate n-channel metal-oxide-semiconductor field-effect transistors
Authors: Dai Chih-Hao , Chang Ting-Chang , Chu Ann-Kuo , Kuo Yuan-Jui , Lo Wen-Hung , Ho Szu-Han , Chen Ching-En , Shih Jou-Miao , Chen Hua-Mao , Dai Bai-Shan , Xia Guangrui , Cheng Osbert , Huang Cheng Tung
Published: March 2011

This letter investigates the impact of static and dynamic stress on threshold voltage (Vth) instability in ultrathin n-channel metal-oxide-semiconductor field-effect transistors with hafnium-based gate stacks. Experimental results indicate Vth shift under dynamic stress is more serious than that under static stress due to charge trapping within the high-k dielectric. Capacitance-voltage techniques demonstrated that electron trapping under dynamic stress was located in the high-k dielectric near the source/drain overlap region rather than throughout the overall dielectric layer. This implies in real circuit operation, the phenomenon of electrons trapped in high-k near the source/drain overlap is the main issue affecting Vth instability.
Integration of nonlinear system of four waves with two velocities in (2 + 1) dimensions by the inverse scattering transform method
Authors: Ismailov Mansur I.
Published: March 2011

In this paper, the inverse scattering problem for the nonstationary Dirac-type system on the whole plane is applied to integration of nonlinear system of four waves with two velocities in (2 + 1) dimensions by using the inverse scattering transform method.
Temporal and spatial study of neon ion emission from a plasma focus device
Authors: Bhuyan M. , Neog N. K. , Mohanty S. R. , Rao C. V. S. , Raole P. M.
Published: March 2011

The temporal and spatial characteristics of the neon ion beam emissions from a low energy plasma focus device have been studied by employing a multiple Faraday cup assembly and the CR-39 track detectors at different angular and axial positions. In addition, the operating gas pressures were also varied to study the temporal and spatial characteristics of the neon ion beam emissions. The Faraday cup analyses show that the ion flux strongly depends on the operating gas pressure as well as the angular positions. The estimated ion energy measurements at the aperture of the Faraday cup indicate that the plasma focus device is a source of polyenergetic ions ranging from approximately a few keV to a few hundreds of keV, irrespective of the angular positions. The exposed CR-39 detectors have shown the formation of multiple ion tracks with diameter ranging from 2 to 13 μm. The populations of lower diameter tracks (2–6 μm) are observed to be more at 0° and 10° angles. It is also noticed that the most populated track counts have shifted toward the higher diameter as the angular positions change from 0° to 70°. The present study enables us to predict a clear picture of ion flux and energy distribution inside the plasma focus chamber that will help to use the device for material irradiation application in a more controlled manner.
Detection of single magnetic nanobead with a nano-superconducting quantum interference device
Authors: Hao L. , Aßmann C. , Gallop J. C. , Cox D. , Ruede F. , Kazakova O. , Josephs-Franks P. , Drung D. , Schurig Th.
Published: March 2011

We report the use of an ultralow noise nano-superconducting quantum interference device (nanoSQUID) to measure the hysteretic magnetization behavior of a single FePt nanobead at a temperature of around 7 K in a magnetic field of only ∼10 mT. We also show that the nanobead can be accurately positioned with respect to the SQUID loop and then removed without affecting SQUID performance. This system is capable of further development with wide applications in nanomagnetism.
Hollow waveguides with low intrinsic photoluminescence fabricated with Ta2O5 and SiO2 films
Authors: Zhao Y. , Jenkins M. , Measor P. , Leake K. , Liu S. , Schmidt H. , Hawkins A. R.
Published: March 2011

A type of integrated hollow core waveguide with low intrinsic photoluminescence fabricated with Ta2O5 and SiO2 films is demonstrated. Hollow core waveguides made with a combination of plasma-enhanced chemical vapor deposition SiO2 and sputtered Ta2O5 provide a nearly optimal structure for optofluidic biofluorescence measurements with low optical loss, high fabrication yield, and low background photoluminescence. Compared to earlier structures made using Si3N4, the photoluminescence background of Ta2O5 based hollow core waveguides is decreased by a factor of 10 and the signal-to-noise ratio for fluorescent nanobead detection is improved by a factor of 12.
Influence of the growth temperature on the performances of strain-balanced quantum cascade lasers
Authors: Bismuto A. , Terazzi R. , Beck M. , Faist Jerome
Published: March 2011

The effect of substrate temperature, during epitaxial growth, on the performances of strain-balanced quantum cascade lasers based on a three quantum well active region and operating at λ≈4.6 μm is presented. Based on a comparison with a density matrix model of these devices, the optimum performances obtained at a growth temperature of 515 °C, are interpreted as arising from a value of the interface roughness correlation length (Λ=85 Å) close to the optimum one computed by the model (Λ=100 Å).
Atomic-resolution scanning transmission electron microscopy through 50-nm-thick silicon nitride membranes
Authors: Ramachandra Ranjan , Demers Hendrix , de Jonge Niels
Published: March 2011

Silicon nitride membranes can be used for windows of environmental chambers for in situ electron microscopy. We report that aberration corrected scanning transmission electron microscopy (STEM) achieved atomic resolution on gold nanoparticles placed on both sides of a 50-nm-thick silicon nitride membrane at 200 keV electron beam energy. Spatial frequencies of 1/1.2 Å were visible for a beam semi-angle of 26.5 mrad. Imaging though a 100-nm-thick membrane was also tested. The achieved imaging contrast was evaluated using Monte Carlo simulations of the STEM imaging of a sample of with a representative geometry and composition.
Nonextensive dust-acoustic solitary waves
Authors: Tribeche M. , Merriche A.
Published: March 2011

The seminal paper of Mamun et al. [Phys. Plasmas 3, 702 (1996)] is revisited within the theoretical framework of the Tsallis statistical mechanics. The nonextensivity may originate from the correlation or long-range interactions in the dusty plasma. It is found that depending on whether the nonextensive parameter q is positive or negative, the dust-acoustic (DA) soliton exhibits compression for q<0 and rarefaction for q>0. The lower limit of the Mach number for the existence of DA solitary waves is greater (smaller) than its Maxwellian counterpart in the case of superextensivity (subextensivity).
AlN
x
Mn
3
: A possible high-temperature soft magnetic material and strongly correlated system
Authors: Lin J. C. , Wang B. S. , Tong P. , Lu W. J. , Zhang L. , Zhu X. B. , Yang Z. R. , Song W. H. , Dai J. M. , Sun Y. P.
Published: March 2011

Structural, magnetic, electrical, and thermal transport properties of antiperovskite compounds AlNxMn3 (x=1,1.1,1.2) have been investigated systematically. With increasing x, the lattice constant increases monotonously while the Curie temperature TC decreases. Both the high TC and small coercive fields consistently indicate AlNxMn3 may be a promising high-temperature soft magnetic material. The resistivity displays T2-dependence below 30 K and the Kadowaki–Woods ratio is about 107.7 μΩ cm/K2, indicating a possible strongly correlated Fermi-liquid behavior in AlNMn3. Further analysis suggests that the electron-type carriers are dominant and the thermal conductivity mainly originates from the lattice contribution.
Enhanced photosensitivity of electro-oxidized epitaxial graphene
Authors: Itkis Mikhail E. , Wang Feihu , Ramesh Palanisamy , Bekyarova Elena , Niyogi Sandip , Chi Xiaoliu , Berger Claire , de Heer Walt A. , Haddon Robert C.
Published: March 2011

We report the enhanced photosensitivity of epitaxial graphene (EG) after electrochemical oxidation in nitric acid. The onset of photoconductivity appears at a photon energy of ∼1.7 eV while the responsivity reaches 2.5 A/W at a wavelength of 470 nm (blue light, energy 2.64 eV) and further increases to 200 A/W in the UV spectral range (3.5 eV, 350 nm). The observed photoresponse is attributed to the formation of deep traps at the electro-oxidized EG interface, which release charge carriers under illumination and prolong the life time of the photocarriers. Potential applications of electro-oxidized EG in ultraviolet photodetection are discussed.
Graphene-based spin logic gates
Authors: Zeng Minggang , Shen Lei , Su Haibin , Zhang Chun , Feng Yuanping
Published: March 2011

Logic operation is the key of digital electronics and spintronics. Based on spin-dependent transport property of zigzag graphene nanoribbons studied using nonequilibrium Green’s function method and density functional theory, we propose a complete set of all-carbon spin logic gates, in which the spin-polarized current can be manipulated by the source-drain voltage and magnetic configuration of the electrodes. These logic gates allow further designs of complex spin logic operations and pave the way for full implementation of spintronics computing devices.
Polarization and angle independent terahertz metamaterials with high Q-factors
Authors: Al-Naib Ibraheem A. I. , Jansen Christian , Born Norman , Koch Martin
Published: March 2011

We propose polarization and angle insensitive metamaterials at terahertz frequencies consisting of two concentric ring resonators with interdigitated fingers placed between the rings. We experimentally demonstrate that the bandstop resonance remains unaffected by changes in both the incident angle and the polarization. Furthermore, high quality-factors of more than 16 are observed as Fano-like modes with small dipole moments are excited. We show that the sharpness of the resonance can be controlled by the number of interdigitated finger pairs. The structures exhibit pronounced normal phase dispersion near the resonance, which renders them attractive candidates for electromagnetic induced transparency and slow light applications.
Molecular phylogeny of Echinodera and Ruteria (Coleoptera:Curculionidae:Cryptorhynchinae) and the parallel speciation of Canary Island weevils along replicate environmental gradients
Authors: Astrin Jonas J. , Stüben Peter E.
Published: March 2011

A molecular phylogeny for the western Palaearctic weevil genus Echinodera Wollaston, 1863 and the former genus Ruteria Roudier, 1954 is presented, combining two mitochondrial genes (CO1 and 16S) in a Bayesian analysis. Special consideration is given to the species of Echinodera from the Canary Islands. Between islands, these are represented by multiple vicariant species that have undergone parallel speciation along replicate environmental gradients on the respective islands. Based on the phylogenetic tree and further data, a number of taxonomic changes is presented: two new species are described, Echinodera montana, sp. nov. from the Canaries (Fuerteventura) and Echinodera bargouensis, sp. nov. from Tunisia. Five species are declared to be synonyms: Echinodera gomerensis Stüben, 2000, syn. nov. = Echinodera praedicta Germann & Stüben, 2006, syn. nov. = Echinodera pseudohystrix Stüben, 2000; Ruteria bellieri epirica Wolf, 2001, syn. nov. = Echinodera tyrrhenica Caldara, 1978, syn. nov. = Acalles bellieri Reiche, 1860; Echindera troodosi Wolf, 2010, syn. nov. = Echinodera cyprica Stüben, 2010. The subgenus Echinodera (Dieckmannia) Stüben, 1998 is a synonym of Echinodera s. str. The genus Ruteria is again declared a subgenus of Echinodera: Echinodera (Ruteria) Roudier, 1954 stat. rev. Two species are transferred to a different subgenus: Echinodera (Ruteria) incognita (Hoffmann, 1956) and Echinodera (Ruteria) cognita Stüben, 2006 (both formerly Echinodera s. str.).
Phylogenetic status of four new species of Acanthobothrium (Cestoda:Tetraphyllidea) parasitic on the wedgefish Rhynchobatus laevis (Elasmobranchii:Rhynchobatidae): implications for interpreting host associations
Authors: Fyler C. A. , Caira J. N.
Published: March 2011

A recent major revision of the elasmobranchs of Australia, which expanded the described fauna from 190 to 307 species, has serious implications for our understanding of the host associations of parasites of Australian elasmobranchs. Most importantly, it questions the identities of the host records for many parasite species. This study focuses on cestodes of the tetraphyllidean genus Acanthobothrium parasitising Rhynchobatus, a batoid genus, the Australian elements of which have recently been revised. Four new cestode species are described from Rhynchobatus laevis (Bloch & Schneider, 1801) from the Northern Territory, Australia. These species differ from their ~160 congeners in several morphological respects. They differ conspicuously from their four Australian congeners also hosted by a Rhynchobatus species, all four of which (i.e. Acanthobothrium bartonae Campbell & Beveridge, 2002, Acanthobothrium gibsoni Campbell & Beveridge, 2002, Acanthobothrium lasti Campbell & Beveridge, 2002 and Acanthobothrium rhynchobatidis Subhapradha, 1955) were reported from Rhynchobatus djiddensis (Forsskål, 1775), a batoid species no longer considered to occur in Australian waters. This suggests that one or both of the other Australian members of Rhynchobatus (i.e. R. australiae Whitley, 1939 and R. palpebratus Compagno & Last, 2008) are likely candidates as hosts for one or more of the latter four species. With respect to the relationships among congeners parasitising the same host species, phylogenetic analyses of sequence data of the D1–D3 region of 28S rDNA for three of the four new cestode species support previous work suggesting that congeners parasitising the same host species are not each other’s closest relatives. This study also serves to emphasise the importance of careful scrutiny of host identities, particularly in systems such as this, in which host taxonomy is under active revision.
VIEWPOINT. Is the Australian subterranean fauna uniquely diverse?
Authors: Guzik Michelle T. , Austin Andrew D. , Cooper Steven J. B. , Harvey Mark S. , Humphreys William F. , Bradford Tessa , Eberhard Stefan M. , King Rachael A. , Leys Remko , Muirhead Kate A. , Tomlinson Moya
Published: March 2011

Australia was historically considered a poor prospect for subterranean fauna but, in reality, the continent holds a great variety of subterranean habitats, with associated faunas, found both in karst and non-karst environments. This paper critically examines the diversity of subterranean fauna in several key regions for the mostly arid western half of Australia. We aimed to document levels of species richness for major taxon groups and examine the degree of uniqueness of the fauna. We also wanted to compare the composition of these ecosystems, and their origins, with other regions of subterranean diversity world-wide. Using information on the number of ‘described’ and ‘known’ invertebrate species (recognised based on morphological and/or molecular data), we predict that the total subterranean fauna for the western half of the continent is 4140 species, of which ~10% is described and 9% is ‘known’ but not yet described. The stygofauna, water beetles, ostracods and copepods have the largest number of described species, while arachnids dominate the described troglofauna. Conversely, copepods, water beetles and isopods are the poorest known groups with less than 20% described species, while hexapods (comprising mostly Collembola, Coleoptera, Blattodea and Hemiptera) are the least known of the troglofauna. Compared with other regions of the world, we consider the Australian subterranean fauna to be unique in its diversity compared with the northern hemisphere for three key reasons: the range and diversity of subterranean habitats is both extensive and novel; direct faunal links to ancient Pangaea and Gondwana are evident, emphasising their early biogeographic history; and Miocene aridification, rather than Pleistocene post-ice age driven diversification events (as is predicted in the northern hemisphere), are likely to have dominated Australia’s subterranean speciation explosion. Finally, we predict that the geologically younger, although more poorly studied, eastern half of the Australian continent is unlikely to be as diverse as the western half, except for stygofauna in porous media. Furthermore, based on similar geology, palaeogeography and tectonic history to that seen in the western parts of Australia, southern Africa, parts of South America and India may also yield similar subterranean biodiversity to that described here.
Intentional intelligence and the intentional intelligence quotient (IIQ): construct development and scale validation integrating mindfulness, self‐agency, and positive thought flow
Authors: Steingard David S. , Dufresne Ronald L.
Published: February 2011

This study follows Braud’s (2009) recommendation for the field of management, spirituality, and religion to produce “standardized assessment instruments”. Our principal goals in this study were to (1) define the construct of intentional intelligence and (2) formulate
and assess a valid and reliable measure of the intentional intelligence quotient (IIQ). Intentional intelligence is defined as one’s ability to (a) identify their current thoughts and (b) choose positive thoughts in one’s mind. We defined the intentional intelligence construct
in light of related constructs of mindfulness, self‐agency, and positive thought flow. We developed and tested the 10‐item IIQ scale as a measure of intentional intelligence alongside measures of comparison constructs. Based on exploratory and confirmatory factor analyses, we
found the IIQ to be a valid and reliable measure.
The relationship between the Personal Ethical Threshold and workplace spirituality
Authors: Comer Debra R. , Vega Gina
Published: February 2011

This article explores the relationship between the Personal Ethical Threshold and workplace spirituality. We begin by reviewing our concept of the Personal Ethical Threshold, or PET, defined as an individual’s vulnerability to organizational pressures that can derail moral intentions.
Next, we consider how individuals resolve their intrapersonal conflict when they violate their moral principles and we explain how to assess the PET. We tie the PET to workplace spirituality by focusing on flow as the expression of spirituality experienced by behaving with integrity, and then
examining how organizations can encourage employees to act according to their values.
Workplace spirituality and expatriate assignments: what are the issues?
Authors: Haslberger Arno
Published: February 2011

Expatriate assignments continue to rise. They pose unique challenges to spirituality researchers. The employing organization reaches deeper into the employee’s private sphere in expatriate assignments than it does in domestic jobs by sponsoring, encouraging, perhaps even requiring
the upheaval of an international move. In addition, the role and expression of spirituality differs from country to country. Not all countries are equally tolerant facing a deviation by expatriates from the expected expressions of spirituality. Therefore, spirituality research requires two
extensions in expatriation studies: first, it must extend further into the private sphere of expatriates and their families; and second, it has to study spirituality at the cultural or societal level. This article discusses the major questions in expatriate assignments from a spirituality
perspective. In doing so, it provides spirituality researchers with a number of research propositions to guide their forays into expatriate studies.
The impact of spirituality on the formation of a leader’s purpose
Authors: Jacobs Gilbert A. , Longbotham Gail J.
Published: February 2011

This article reports a study of how 10 highly influential Christian leaders formed their higher purpose. Using the phenomenological approach and of Moustakas and grounded theory procedures, the study results suggest that when these leaders experienced cognitive dissonance because of
their spiritual formation and conditions they perceived in the environment, they formed a higher purpose aimed at reducing the dissonance. Similar to the behavioral model of Ajzen and Fishbein, evidence from this study suggests that spiritual beliefs and the encouragement of others influences
the formation of a leader’s higher purpose (intention), which, in turn, informs the vision that they communicate (behavior) to others.
Manifold domain structure of double films with perpendicular magnetic anisotropy
Authors: Coffey D , Diez-Ferrer J L , Corredor E C , Arnaudas J I , Ciria M
Published: March 2011

We present epitaxial structures made of twin nickel blocks with perpendicular magnetic anisotropy separated by a copper layer which, for some values of this interleaving layer, show domain structures with four levels of contrast in magnetic force microscopy images. This manifold domain structure implies that the magnetization in the Ni blocks, in addition to the parallel orientation, undergoes a non-collinear configuration with respect to each other. To explain this result we consider a magnetoelastic domain structure with M in the plane that can elude the clamping done by the substrate with an average strain of −42 × 10−6 (≈70% of the bulk value). Thus, the out-of-plane anisotropy is balanced and a biquadratic exchange coupling can stabilize the non-collinear domain configurations between the Ni blocks.
The influence of radio-frequency discharge geometry on O2(a 1Δ) production
Authors: Woodard B S , Day M T , Zimmerman J W , Benavides G F , Palla A D , Carroll D L , Verdeyen J T , Solomon W C
Published: March 2011

Experiments and modelling have led to continued enhancements in the electric oxygen–iodine laser system. This continuous wave laser operating on the 1315 nm transition of atomic iodine is pumped by the production of O2(a) in a radio-frequency discharge in an O2/He/NO gas mixture. New discharge geometries have led to improvements in O2(a) production and efficiency. Studies of electrode gap continue to improve O2(a) production at high pressures, and measurements of species exiting the discharge have expanded the understanding of this system. Some of these improvements have already been applied to the laser system, and other advances will be utilized to continue scaling the system to higher laser powers. Over 1 kW of power stored in O2(a) has been demonstrated in both the rectangular cross-section and multi-circular tube discharges.
Enhancement of efficiency and stability of phosphorescent OLEDs based on heterostructured light-emitting layers
Authors: Chin Byung Doo
Published: March 2011

The light-emitting efficiency and stability of a phosphorescent organic light-emitting device (OLED), whose emission characteristics are strongly dominated not only by the energy transfer but also by the charge carrier trapping influenced by heterostructured emissive layers, are studied. The variation of the material combination of the heterostructured emitter, both for mixed and double layer configuration, affects the charge injection behaviour, luminous efficiency and stability. Both double and mixed emitter configurations yield low-voltage and high-efficiency behaviour (51 lm W−1 at 1000 cd m−2; 30 lm W−1 at 10 000 cd m−2). Such an improvement in power efficiency at elevated brightness is sufficiently universal, while the enhancement of device half-lifetime is rather sensitive to the circumstantial layout of heterostructural emitters. With an optimal mixture of hole-transport type and electron-transport type, a half-lifetime of more than 2500 h at 4000 cd m−2 is obtained, which is 8 times the half-lifetime of control devices with a single emitter structure. The origin and criterion for enhancement of efficiency and lifetime are discussed in terms of the carrier transport behaviour with a specific device architecture.
Squeeze effect and coherent coupling behaviour in photonic crystal vertical-cavity surface-emitting lasers
Authors: Liu An-Jin , Chen Wei , Zhou Wen-Jun , Jiang Bin , Fu Feiya , Qu Hong-Wei , Zheng Wan-Hua
Published: March 2011

The impact of air holes on the field profile in photonic crystal vertical-cavity surface-emitting lasers (PC-VCSELs) is investigated theoretically and experimentally. The three-dimensional finite-difference time-domain method is used to demonstrate the squeeze effect induced by air holes on the field profile at small etching depths and the diffraction caused by air holes in PC-VCSELs. In far field patterns (FFPs) of single-mode PC-VCSELs, there are six sidelobes surrounding the main lobe due to the coherent coupling between the diffractive light from air holes and the light from the central defect. In the experiments, the light from air holes has the same spectrum as that from the central defect. The measured FFPs are the same as the calculated FFPs. Both the measured spectra and the measured FFPs show that the light from air holes has the same wavelength and polarization as the light from the central defect, which confirms that the light from air holes is the diffractive light caused by air holes.
Numerical simulation of the creation of a tapered plasma channel by a nonuniform large magnetic field
Authors: Wang C M , Qian Y J , Sun J , Teng Q , Chen C Q
Published: March 2011

In order to resolve the dephasing problem in laser wakefield acceleration, a tapered plasma guiding channel (TPGC) is proposed which is verified through magnetohydrodynamic (MHD) simulation. TPGC is created by means of laser heating combining an axially increasing external magnetic field. MHD simulation shows that a locally strong magnetic field prevents the thermal energy transport crossing the field lines, which consequently leads to a pressure buildup. The pressure gradient expels the plasma radially and tapers the density axially. A tapered plasma with a density variation from 2 × 1018 to 8 × 1017 cm−3 within a 6 cm channel is established. Propagating in the tapered plasma channel, the energy of an accelerated electron is expected to be significantly enhanced.
Temperature-dependent electron microscopy study of Au thin films on Si (1 0 0) with and without a native oxide layer as barrier at the interface
Authors: Rath A , Dash J K , Juluri R R , Rosenauer A , Satyam P V
Published: March 2011

Real-time electron microscopy observation on morphological changes in gold nanostructures deposited on Si (1 0 0) surfaces as a function of annealing temperatures has been reported. Two types of interfaces with silicon substrates were used prior to gold thin film deposition: (i) without native oxide and on ultra-clean reconstructed Si surfaces and (ii) with native oxide covered Si surfaces. For ≈2.0 nm thick Au films deposited on reconstructed Si (1 0 0) surfaces using the molecular beam epitaxy method under ultra-high vacuum conditions, aligned four-fold symmetric nanogold silicide structures formed at relatively lower temperatures (compared with the one with native oxide at the interface). For this system, 82% of the nanostructures were found to be nanorectangle-like structures with an average length of ≈27 nm and aspect ratio of 1.13 at ≈700 °C. For ≈5.0 nm thick Au films deposited on Si (1 0 0) surface with native oxide at the interface, the formation of a rectangular structure was observed at higher temperatures (≈850 °C). At these high temperatures, desorption of gold silicide followed the symmetry of the substrate. Native oxide at the interface was found to act like a barrier for the inter-diffusion phenomena. Structural characterization was carried out using advanced electron microscopy methods.
The spindle assembly function ofCaenorhabditis eleganskatanin does not require microtubule-severing activity
Authors: McNally Karen Perry , McNally Francis J.
Published: March 2011

Katanin is a heterodimeric microtubule-severing protein that is conserved among eukaryotes. Loss-of-function mutations in the Caenorhabditis elegans katanin catalytic subunit, MEI-1, cause specific defects in female meiotic spindles. To determine the relationship between katanin’s microtubule-severing activity and its role in meiotic spindle formation, we analyzed the MEI-1(A338S) mutant. Unlike wild-type MEI-1, which mediated disassembly of microtubule arrays in Xenopus fibroblasts, MEI-1(A338S) had no effect on fibroblast microtubules, indicating a lack of microtubule-severing activity. In C. elegans, MEI-1(A338S) mediated assembly of extremely long bipolar meiotic spindles. In contrast, a nonsense mutation in MEI-1 caused assembly of meiotic spindles without any poles as assayed by localization of the spindle-pole protein, ASPM-1. These results indicated that katanin protein, but not katanin’s microtubule-severing activity, is required for assembly of acentriolar meiotic spindle poles. To understand the nonsevering activities of katanin, we characterized the N-terminal domain of the katanin catalytic subunit. The N-terminal domain was necessary and sufficient for binding to the katanin regulatory subunit. The katanin regulatory subunit in turn caused a dramatic change in the microtubule-binding properties of the N-terminal domain of the catalytic subunit. This unique bipartite microtubule-binding structure may mediate the spindle-pole assembly activity of katanin during female meiosis.
Identifying discriminative classification-based motifs in biological sequences
Authors: Vens Celine , Rosso Marie-Noëlle , Danchin Etienne G. J.
Published: March 2011

Motivation: Identification of conserved motifs in biological sequences is crucial to unveil common shared functions. Many tools exist for motif identification, including some that allow degenerate positions with multiple possible nucleotides or amino acids. Most efficient methods available today search conserved motifs in a set of sequences, but do not check for their specificity regarding to a set of negative sequences.

Results: We present a tool to identify degenerate motifs, based on a given classification of amino acids according to their physico-chemical properties. It returns the top K motifs that are most frequent in a positive set of sequences involved in a biological process of interest, and absent from a negative set. Thus, our method discovers discriminative motifs in biological sequences that may be used to identify new sequences involved in the same process. We used this tool to identify candidate effector proteins secreted into plant tissues by the root knot nematode Meloidogyne incognita. Our tool identified a series of motifs specifically present in a positive set of known effectors while totally absent from a negative set of evolutionarily conserved housekeeping proteins. Scanning the proteome of M.incognita, we detected 2579 proteins that contain these specific motifs and can be considered as new putative effectors.

Availability and Implementation: The motif discovery tool and the proteins used in the experiments are available at http://dtai.cs.kuleuven.be/ml/systems/merci.

Contact:  celine.vens@cs.kuleuven.be

Supplementary Information:  Supplementary data are available at Bioinformatics online.