bluuebunny/crossref_metadata_2025 huggingface dataset:
Laser induced extraplanar propulsion for three-dimensional microfabrication
Authors: Birnbaum A. J. , Piqué A.
Published: March 2011

The laser induced extraplanar propulsion process is presented for the creation of controllable three-dimensional deformation of on-substrate components. It is demonstrated that the process is compatible with transparent substrates and ductile materials and is highly controllable in terms of the desired deformation via the adjustment of incident laser energy density. Copper films with thicknesses varying from 0.1–1 μm are deformed over bending angles ranging from 0°–180°. A 355 nm laser at fluences ranging from 10–40 mJ/cm2 is used in conjunction with an indium-tin-oxide propulsion layer to demonstrate the process. Characterization is performed via electron and laser confocal microscopy.
Tuning perpendicular magnetic anisotropy and coercivity of L1-FePt nanocomposite film by interfacial manipulation
Authors: Feng Chun , Mei Xuezhen , Yang Meiyin , Li Ning , Jiang Yong , Yu Guanghua , Wang Fuming
Published: March 2011

Based on the interfacial anisotropy manipulation of multilayer structure and the orientation manipulation of surfactant Au atoms, Fe/Pt/Au multilayers were designed to achieve tunable perpendicular magnetic anisotropy (PMA) of L10-FePt nanocomposite films. In the mean time, the ordering degree of the Fe/Pt/Au multilayers was modified by adjusting the defect concentration in the film, which can be controlled by using different multilayer structures and by the diffusion of Au atoms. This makes the coercivity (HC) of L10-FePt nanocomposite films able to be tailored. Thus a L10-FePt nanocomposite film with high PMA and tunable HC was constructed that provides important experimental data for preparing writable FePt perpendicular magnetic recording media.
A comparison of fluid and kinetic models of steady magnetic reconnection
Authors: Brackbill J. U.
Published: March 2011

For steady magnetic reconnection in a current sheet, a two-fluid model that includes tensor pressure is compared with kinetic simulations. The kinetic simulations model a Harris sheet in two dimensions with prescribed inflow and free outflow. The two-fluid model provides solutions along the symmetry line from the inflow boundary to the flow stagnation point. The model assumes incompressibility and neglects the Hall current. Profiles from the inflow boundary to the X-point of the out-of-plane electric field and the terms in Ohm’s law that contribute to it from the simulation and from the fluid model agree in almost every detail. The best agreement is obtained when relaxation of the tensor pressure to isotropy occurs on time scales comparable to the electron plasma period. On ion scales, the two-fluid and kinetic simulations give similar results when finite Larmor radius physics is included. The ion pressure relaxation scales linearly with the ion/electron mass ratio.
Effect of energetic electrons on dust charging in hot cathode filament discharge
Authors: Kakati B. , Kausik S. S. , Saikia B. K. , Bandyopadhyay M.
Published: March 2011

The effect of energetic electrons on dust charging for different types of dust is studied in hydrogen plasma. The hydrogen plasma is produced by hot cathode filament discharge method in a dusty plasma device. A full line cusped magnetic field cage is used to confine the plasma elements. To study the plasma parameters for various discharge conditions, a cylindrical Langmuir probe having 0.15 mm diameter and 10.0 mm length is used. An electronically controlled dust dropper is used to drop the dust particles into the plasma. For different discharge conditions, the dust current is measured using a Faraday cup connected to an electrometer. The effect of secondary emission as well as discharge voltage on charging of dust grains in hydrogen plasma is studied with different dust.
Narrow spectral linewidth from single site-controlled In(Ga)As quantum dots with high uniformity
Authors: Huggenberger A. , Heckelmann S. , Schneider C. , Höfling S. , Reitzenstein S. , Worschech L. , Kamp M. , Forchel A.
Published: March 2011

We present narrow spectral linewidth from single site-controlled In(Ga)As quantum dots (QDs) grown on nanoholes, which were defined by electron beam lithography on a (100) GaAs substrate. The long-range ordering of uncapped QDs is confirmed by electron microscopy whereas the ordering of capped QDs is visualized by atomic force microscopy. We find a small inhomogeneous broadening of 14.4 meV for the ensemble emission of site-controlled QDs with 300 nm lattice period. The photoluminescence from the excitonic transitions of single site-controlled QDs exhibits linewidth values down to 43 μeV, which is promising for the investigation of pronounced cavity quantum electrodynamic effects in scalable QD-microresonator systems.
Charge transport and trapping in organic field effect transistors exposed to polar analytes
Authors: Duarte Davianne , Sharma Deepak , Cobb Brian , Dodabalapur Ananth
Published: March 2011

Pentacene based organic thin-film transistors were used to study the effects of polar analytes on charge transport and trapping behavior during vapor sensing. Three sets of devices with differing morphology and mobility (0.001−0.5 cm2/V s) were employed. All devices show enhanced trapping upon exposure to analyte molecules. The organic field effect transistors with different mobilities also provide evidence for morphology dependent partition coefficients. This study helps provide a physical basis for many reports on organic transistor based sensor response.
Orientation dependence of charge transfer for C60 on Cu(100)
Authors: Daughton D. R. , Gupta J. A.
Published: March 2011

Scanning tunneling microscopy was used to characterize the lowest unoccupied molecular orbitals (LUMO), up to LUMO+3, of individual C60 molecules within monolayer films on Cu(100). On this surface C60 orients in four distinct configurations with respect to the substrate. Tunneling spectroscopy and spectroscopic imaging were used to identify the energies and spatial distributions of the molecular orbitals. We find that the LUMO shifts by ∼200 meV depending on the orientation of the molecule, which suggests charge transfer between the surface and molecule is orientation dependent. Orientation-dependent shifts were also observed for the higher unoccupied molecular orbitals.
Low-frequency noise in junctionless multigate transistors
Authors: Jang Doyoung , Lee Jae Woo , Lee Chi-Woo , Colinge Jean-Pierre , Montès Laurent , Lee Jung Il , Kim Gyu Tae , Ghibaudo Gérard
Published: March 2011

Low-frequency noise in n-type junctionless multigate transistors was investigated. It can be well understood with the carrier number fluctuations whereas the conduction is mainly limited by the bulk expecting Hooge mobility fluctuations. The trapping/release of charge carriers is related not only to the oxide-semiconductor interface but also to the depleted channel. The volume trap density is in the range of 6–30×1016 cm−3 eV−1, which is similar to Si–SiO2 bulk transistors and remarkably lower than in high-k transistors. These results show that the noise in nanowire devices might be affected by additional trapping centers.
Attaining persistent field-free control of open and closed quantum systems
Authors: Anson Erik , Beltrani Vincent , Rabitz Herschel
Published: March 2011

Persistent quantum control (PQC) aims to maintain an observable objective value over a period of time following the action of an applied field. This paper assesses the feasibility of achieving PQC for arbitrary finite-level systems and observables. The analysis is carried out independent of the particular method used for state preparation. The PQC behavior is optimized over the set of physically accessible prepared states for both open and closed systems. The quality of observable value persistence in the postcontrol period was found to vary with the required duration of persistence, the system temperature, the chosen observable operator, and the energy levels of the system. The alignment of a rigid diatomic rotor is studied as a model system. The theoretical estimates of PQC behavior are encouraging and suggest feasible exploration in the laboratory using currently available technology.
Mode signature and stability for a Hamiltonian model of electron temperature gradient turbulence
Authors: Tassi E. , Morrison P. J.
Published: March 2011

Stability properties and mode signature for equilibria of a model of electron temperature gradient (ETG) driven turbulence are investigated by Hamiltonian techniques. After deriving new infinite families of Casimir invariants, associated with the noncanonical Poisson bracket of the model, a sufficient condition for stability is obtained by means of the Energy-Casimir method. Mode signature is then investigated for linear motions about homogeneous equilibria. Depending on the sign of the equilibrium “translated” pressure gradient, stable equilibria can either be energy stable, i.e., possess definite linearized perturbation energy (Hamiltonian), or spectrally stable with the existence of negative energy modes. The ETG instability is then shown to arise through a Kreĭn-type bifurcation, due to the merging of a positive and a negative energy mode, corresponding to two modified drift waves admitted by the system. The Hamiltonian of the linearized system is then explicitly transformed into normal form, which unambiguously defines mode signature. In particular, the fast mode turns out to always be a positive energy mode, whereas the energy of the slow mode can have either positive or negative sign. A reduced model with stable equilibria shear flow that possess a continuous spectrum is also analyzed and brought to normal form by a special integral transform. In this way it is seen how continuous spectra can have signature as well.
Stabilization of the resistive wall mode instability by trapped energetic particles
Authors: Hao G. Z. , Liu Y. Q. , Wang A. K. , Jiang H. B. , Lu Gaimin , He H. D. , Qiu X. M.
Published: March 2011

A theoretical model for investigating the effect of the trapped energetic particles (EPs) on the resistive wall mode (RWM) instability is proposed. The results demonstrate that the trapped EPs have a dramatic stabilizing effect on the RWM because of resonant interaction between the mode and the magnetic precession drift motion of the trapped EPs. The results also show that the effect of the trapped EPs depends on the wall position. In addition, the stabilizing effect becomes stronger when the plasma rotation is taken into account. For sufficiently fast plasma rotation, the trapped EPs can lead to the complete stabilization of the RWM. Furthermore, the trapped EPs can induce a finite real frequency of the RWM in the absence of plasma rotation.
Non-Markovian finite-temperature two-time correlation functions of system operators: Beyond the quantum regression theorem
Authors: Goan Hsi-Sheng , Chen Po-Wen , Jian Chung-Chin
Published: March 2011

An extremely useful evolution equation that allows systematically calculating the two-time correlation functions (CF's) of system operators for non-Markovian open (dissipative) quantum systems is derived. The derivation is based on perturbative quantum master equation approach, so non-Markovian open quantum system models that are not exactly solvable can use our derived evolution equation to easily obtain their two-time CF's of system operators, valid to second order in the system–environment interaction. Since the form and nature of the Hamiltonian are not specified in our derived evolution equation, our evolution equation is applicable for bosonic and/or fermionic environments and can be applied to a wide range of system–environment models with any factorized (separable) system–environment initial states (pure or mixed). When applied to a general model of a system coupled to a finite-temperature bosonic environment with a system coupling operator L in the system–environment interaction Hamiltonian, the resultant evolution equation is valid for both L = L† and L ≠ L† cases, in contrast to those evolution equations valid only for L = L† case in the literature. The derived equation that generalizes the quantum regression theorem (QRT) to the non-Markovian case will have broad applications in many different branches of physics. We then give conditions on which the QRT holds in the weak system–environment coupling case and apply the derived evolution equation to a problem of a two-level system (atom) coupled to the finite-temperature bosonic environment (electromagnetic fields) with L ≠ L†.
Identification of the double acceptor levels of the mercury vacancies in HgCdTe
Authors: Gemain F. , Robin I. C. , De Vita M. , Brochen S. , Lusson A.
Published: March 2011

Photoluminescence and temperature-dependent Hall measurements of nonintentionally doped HgCdTe epilayers were compared. These films were grown by liquid phase epitaxy and postannealed under different conditions as follows: a p-type annealing was used to control the mercury vacancy concentration and a n-type annealing under saturated Hg atmosphere was used to fill the mercury vacancies. The comparison of the photoluminescence measurements with Hall effect measurements allows us to identify the two acceptor energy levels of the mercury vacancy and to evidence its “negative-U” property corresponding to a stabilization of the ionized state V− of the mercury vacancy compared to its neutral state V0.
The inversely proportional relationship in the asymmetric transport of a diblock co-oligomer junction
Authors: Cui B. , Fang C. F. , Zhai Y. X. , Yin S. , Gao K. , Liu D. S.
Published: March 2011

We investigate electron transport properties and the mechanism of current rectification effect in a diblock co-oligomer (diprimidinyl-diphenyl) molecular junction under electron-lattice coupling effect, using an extended Su–Schrieffer–Heeger tight-binding model combined with nonequilibrium Green’s function formalism. We find an inversely relationship between the positive threshold bias and the molecular dipole moment under proper electron-lattice coupling.
Neoclassical polarization drift of collisionless single ion in tokamaks with arbitrary time-varying radial electric field
Authors: Pan Chengkang , Xiao Xiaotao , Wang Shaojie
Published: March 2011

An improved theory for the neoclassical polarization drift of the collisionless single ion with the arbitrary time-varying radial electric field is presented. A guiding-center motion code is used to numerically study the neoclassical polarization drift of a collisionless single ion in a model tokamak geometry. The results from the improved theory are compared with the numerical results and they agree with each other very well. The improved theory can be used to study the neoclassical polarization drift due to the fast time-varying radial electric field.
Full band structure calculation of two-photon indirect absorption in bulk silicon
Authors: Cheng J. L. , Rioux J. , Sipe J. E.
Published: March 2011

Degenerate two-photon indirect absorption in silicon is an important limiting effect on the use of silicon structures for all-optical information processing at telecommunication wavelengths. We perform a full band structure calculation to investigate two-photon indirect absorption in bulk silicon, using a pseudopotential description of the energy bands and an adiabatic bond charge model to describe phonon dispersion and polarization. Our results agree well with some recent experimental results. The transverse acoustic/optical phonon-assisted processes dominate.
Quantum dot spectroscopy of proximity-induced superconductivity in a two-dimensional electron gas
Authors: Deon F. , Pellegrini V. , Giazotto F. , Biasiol G. , Sorba L. , Beltram F.
Published: March 2011

We report the realization of a hybrid superconductor-quantum dot device by means of top-down nanofabrication starting from a two-dimensional electron gas in a InGaAs/InAlAs semiconductor heterostructure. The quantum dot is defined by electrostatic gates placed within the normal region of a planar Nb–InGaAs quantum well-Nb junction. Measurements in the regime of strong Coulomb blockade as well as cotunneling spectroscopy allow to directly probe the proximity-induced energy gap in a ballistic two-dimensional electron gas coupled to superconductors.
HXeOBr in a xenon matrix
Authors: Khriachtchev Leonid , Tapio Salla , Domanskaya Alexandra V. , Räsänen Markku , Isokoski Karoliina , Lundell Jan
Published: March 2011

We report on a new noble-gas molecule HXeOBr prepared in a low-temperature xenon matrix from the HBr and N2O precursors by UV photolysis and thermal annealing. This molecule is assigned with the help of deuteration experiments and ab initio calculations including anharmonic methods. The H−Xe stretching frequency of HXeOBr is observed at 1634 cm−1, which is larger by 56 cm−1 than the frequency of HXeOH identified previously. The experiments show a higher thermal stability of HXeOBr molecules in a xenon matrix compared to HXeOH.
Electric conductivities of 1:1 electrolytes in high-temperature ethanol along the liquid–vapor coexistence curve. II. Tetraalkylammonium bromides
Authors: Matsui Tomoko , Hoshina Taka-aki , Tsuchihashi Noriaki , Ibuki Kazuyasu , Ueno Masakatsu
Published: March 2011

The molar electrolyte conductivities of dilute solutions of the tetramethyl, tetraethyl, tetra-n-propyl, and tetra-n-butylammonium bromides were measured in ethanol along the liquid–vapor coexistence curve up to 160 °C. The limiting molar electrolyte conductivities and the molar association constants were obtained from the analysis of the concentration dependence of the conductivity. The ionic friction coefficients were estimated from the electrolyte conductivities. On the basis of the present data together with the literature ones at higher densities (lower temperatures) and comparisons with the continuum dielectric friction theory, the density (temperature) dependence of the translational friction coefficients of the tetraalkylammonium ions were discussed in the range of 0.810 ⩾ ρ ⩾ 0.634 g cm−3 (−5 °C ⩽ t ⩽ 160 °C). The dielectric friction effect was important for the tetramethylammonium ion in the whole range studied. The tetraethylammonium ion showed a relatively small friction coefficient in ambient condition indicating the structure-loosening effect around the ion, while the dielectric friction effect became more important as the density reduces and the temperature raises. For the tetra-n-butylammonium ion, the friction coefficients were determined mainly by the bulky size effect. The tetra-n-propylammonium ion showed an intermediate tendency between the tetraethylammonium and tetra-n-butylammonium ions.
Thermal quenching of single localized excitons in GaInNAs layers
Authors: Latkowska M. , Kudrawiec R. , Sęk G. , Misiewicz J. , Ibáñez J. , Henini M. , Hopkinson M.
Published: March 2011

The authors applied the temperature-dependent microphotoluminescence to study the thermal quenching of exciton lines related to localized emission from GaInNAs. It has been observed that the dispersion of localization energy is very strong (∼0–150 meV) whereas the activation energy of each individual line is the same within the experimental error (∼6 meV). This suggests that the main source of sharp line features are excitons localized on deep donor(acceptor)like states. At low temperatures these states can participate in radiative recombination due to the coulomb attraction between electrons and holes whereas at higher temperatures they still trap carriers but these carriers recombine nonradiatively.
Strong water-mediated friction asymmetry and surface dynamics of zwitterionic solids at ambient conditions: L-alanine as a case study
Authors: Segura J. J. , Verdaguer A. , Garzón L. , Barrena E. , Ocal C. , Fraxedas J.
Published: March 2011

Water molecules strongly interact with freshly cleaved (011) surfaces of L-alanine single crystals at low relative humidity (below 10%) promoting diffusion of L-alanine molecules. Species mobility is enhanced above ∼40% leading to the formation of two-dimensional islands with long-range order through Ostwald ripening. Scanning force microscopy experiments reveal that both, islands and terraces, are identical in nature (composition and crystallographic structure) but a relevant friction asymmetry appearing upon water–surface interaction evidences that orientation dependent properties exist between them at the molecular level. We interpret this observation as due to water incorporation in the topmost surface crystal structure. Eventually, for high humidity values, surface dissolution and roughening occur.
Effects of exothermic chemical reaction on the photoacoustic effect from particulate suspensions
Authors: Park Han Jung , Wu Binbin , Diebold Gerald J.
Published: March 2011

Irradiation of chemically reactive particulate suspensions by high power, pulsed laser radiation initiates reactions at the sites of the particles so that besides the absorbed optical energy, chemical energy is liberated. In addition to the release of chemical energy, chemical reaction can result in gas production both of which result in enhancement in the amplitude of the photoacoustic effect. Here we report photoacoustic and transient grating experiments with colloidal C in mixtures of H2O2 with H2O. The inclusion of H2O2 in an aqueous C suspension changes the normally endothermic reaction of C with H2O into the highly exothermic reaction of C with H2O2 leading to both an enhanced photoacoustic effect and an increase in light emission from the suspension. As well, laser-initiated exothermic reactions in suspensions of C with CH3NO2 and particulate Hg(CNO)2 in H2O are shown to result in greatly enhanced photoacoustic signal amplitudes.
Tunable ultraviolet vertically-emitting organic laser
Authors: Forget Sébastien , Rabbani-Haghighi Hadi , Diffalah Nordine , Siove Alain , Chénais Sébastien
Published: March 2011

A solid-state organic thin-film laser with intracavity frequency doubling is reported. Tunable ultraviolet emission from 309 to 322 nm is achieved from a vertical external cavity surface-emitting organic laser, with 2% efficiency (1 μJ at 315 nm). The laser comprises a poly(methyl methacrylate) layer doped with Rhodamine 640, spun-cast onto a plane mirror, a remote concave mirror, a nonlinear crystal, and a dichroic separator. The output is spectrally narrow (<0.5 nm full width at half maximum) and tunable through phase-matching selection of the fundamental radiation lasing modes. These results highlight a low-cost and portable alternative to tunable UV laser sources, useful for spectroscopic applications.
Scaling of superdomain bands in ferroelectric dots
Authors: McGilly L. J. , Gregg J. M.
Published: March 2011

Bundles of 90° stripe domains have been observed to form into distinct groups, or bands, in mesoscale BaTiO3 single crystal dots. Vector piezoresponse force microscopy (PFM) shows that each band region, when considered as a single entity, possesses a resolved polarization that lies approximately along the ⟨110⟩pseudocubic direction; antiparallel alignment of this resultant polarization in adjacent bands means that these regions can be considered as 180° “superdomains.” For dots with sidewall dimensions below ∼2 μm, Landau–Kittel like scaling in the width of these superdomains was observed, strongly suggesting that they form in response to lateral depolarizing fields. In larger dot structures, scaling laws break down. We have rationalized these observations by considering changes in the driving force for the adoption of equilibrium superdomain periodicities implied by Landau–Kittel-free energy models; we conclude that the formation of ordered bands of superdomains is a uniquely meso/nanoscale phenomenon. We also note that the superdomain bands found by PFM imaging in air contrast with the quadrant arrangements seen previously by Schilling et al. [Nano Lett., 9, 3359 (2009)] through transmission electron microscopy imaging in vacuum. The importance of the exact nature of the boundary conditions in determining the domain patterns that spontaneously form in nanostructures is therefore clearly implied.
Small clusters of aluminum and tin: Highly correlated calculations and validation of density functional procedures
Authors: Drebov Nedko , Ahlrichs Reinhart
Published: March 2011

We present results of molecular electronic structure treatments of multireference configuration interaction (MRCI) type for clusters Aln and Snn in the range up to n = 4, and of coupled cluster singles and doubles with perturbative triples corrections (CCSD(T)) type in the range up to n = 10. Basis sets of quadruple zeta size are employed, computed energy differences, such as cohesive energies, \documentclass[12pt]{minimal}\begin{document}$\rm E_{coh}$\end{document}E coh , or dissociation energies for the removal of a single atom, \documentclass[12pt]{minimal}\begin{document}$\rm D_e$\end{document}De, differ from the complete basis set limit by only a few 0.01 eV. MRCI and CCSD(T) results are then compared to those obtained from density functional theory (DFT) treatments, which show that all computational procedures agree with the general features of \documentclass[12pt]{minimal}\begin{document}$\rm D_e$\end{document}De and \documentclass[12pt]{minimal}\begin{document}$\rm E_{coh}$\end{document}E coh . The best agreement of DFT with CCSD(T) is found for the meta-GGA (generalized gradient approximation) TPSS (Tao, Perdew, Staroverov, Scuseria) for which \documentclass[12pt]{minimal}\begin{document}$\rm D_e$\end{document}De differs from CCSD(T) by at most 0.15 eV for Aln and 0.21 eV for Snn. The GGA PBE (Perdew, Burke, Ernzerhof) is slightly poorer with maximum deviations of 0.23 and 0.24 eV, whereas hybrid functionals are not competitive with GGA and meta-GGA functionals. A general conclusion is that errors of \documentclass[12pt]{minimal}\begin{document}$\rm D_e$\end{document}De and/or energy differences of isomers computed with DFT procedures may easily reach 0.2 eV and errors for cohesive energies \documentclass[12pt]{minimal}\begin{document}$\rm E_{coh}$\end{document}E coh 0.1 eV.
Revealing the volume magnetic anisotropy of Fe films epitaxied on GaAs(001) surface
Authors: Chen G. , Zhu J. , Li J. , Liu F. Z. , Wu Y. Z.
Published: March 2011

The in-plane magnetic anisotropy in Fe films grown on GaAs(001) was investigated quantitatively by the magneto-optic Kerr effect with a rotating magnetic field. The clear 1/dFe relation of the uniaxial magnetic anisotropy indicates a surprising volume contribution with easy axis along the GaAs [11¯0] direction. Such volume anisotropy was found to be sensitive to the growth temperature and also strongly correlate with the interface anisotropy. Our results may introduce a new aspect for further understanding the origin of uniaxial magnetic anisotropy in Fe/GaAs(001) system.
Sustained mechanical self-oscillation of carbon nanotube cantilever by phase locked loop with optomechanical heterodyne
Authors: Yoshinaka Atsushi , Arie Takayuki , Akita Seiji
Published: March 2011

We have proposed an optomechanical heterodyne method for measurements of carbon nanotube (CNT) cantilever vibrations and demonstrated the sustained mechanical self-oscillation of the CNT cantilever by the combination of the phase locked loop and the proposed method. Mass sensitivities less than 100 zg were easily achieved in vacuum for long term (∼100 s) deviation and even in air for short term (∼1 s) deviation. Furthermore, the CNT cantilever with the phase locked loop detection is achieved with the very high force sensitivity of a force gradient of ∼10−10 N/m, which is fifth orders magnitude higher than that for the conventional noncontact atomic force microscopy.
Water coordination structures and the excess free energy of the liquid
Authors: Merchant Safir , Shah Jindal K. , Asthagiri D.
Published: March 2011

We assess the contribution of each coordination state to the hydration free energy of a distinguished water molecule, the solute water. We define a coordination sphere, the inner-shell, and separate the hydration free energy into packing, outer-shell, and local, solute-specific (chemical) contributions. The coordination state is defined by the number of solvent water molecules within the coordination sphere. The packing term accounts for the free energy of creating a solute-free coordination sphere in the liquid. The outer-shell contribution accounts for the interaction of the solute with the fluid outside the coordination sphere and it is accurately described by a Gaussian model of hydration for coordination radii greater than the minimum of the oxygen–oxygen pair-correlation function: theory helps identify the length scale to parse chemical contributions from bulk, nonspecific contributions. The chemical contribution is recast as a sum over coordination states. The nth term in this sum is given by the probability pn of observing n water molecules inside the coordination sphere in the absence of the solute water times a factor accounting for the free energy, Wn, of forming an n-water cluster around the solute. The pn factors thus reflect the intrinsic properties of the solvent while Wn accounts for the interaction between the solute and inner-shell solvent ligands. We monitor the chemical contribution to the hydration free energy by progressively adding solvent ligands to the inner-shell and find that four-water molecules are needed to fully account for the chemical term. For a chemically meaningful coordination radius, we find that W4 ≈ W1 and thus the interaction contribution is principally accounted for by the free energy for forming a one-water cluster, and intrinsic occupancy factors alone account for over half of the chemical contribution. Our study emphasizes the need to acknowledge the intrinsic solvent properties in interpreting the hydration structure of any solute, with particular care in cases where the solute–solvent interaction strength is similar to that between the solvent molecules.
Communication: The effect of dispersion corrections on the melting temperature of liquid water
Authors: Yoo Soohaeng , Xantheas Sotiris S.
Published: March 2011

The melting temperature (Tm) of liquid water with the Becke–Lee–Yang–Parr (BLYP) density functional including dispersion corrections (BLYP-D) and the Thole-type, version 3 (TTM3-F) ab-initio based flexible, polarizable classical potential is reported via constant pressure and constant enthalpy (NPH) molecular dynamics simulations of an ice Ih-liquid coexisting system. Dispersion corrections to BLYP lower Tm to about 360 K, a large improvement over the value of Tm > 400 K previously obtained with the original BLYP functional under the same simulation conditions. For TTM3-F, Tm = 248 K from classical molecular dynamics simulations.
Band offsets between SiO2 and phase change materials in the (GeTe)x(Sb2Te3)1−x pseudobinary system
Authors: Fang Lina Wei-Wei , Zhao Rong , Zhang Zheng , Pan Jisheng , Shi Luping , Chong Tow-Chong , Yeo Yee-Chia
Published: March 2011

The energy band alignment between stoichiometric phase change alloys residing along the pseudobinary line of GeTe–Sb2Te3[(GeTe)x(Sb2Te3)1−x] and SiO2 was obtained employing high-resolution x-ray photoelectron spectroscopy. The valence band offsets were determined using both the core-level spectra and valence band spectra in the analysis. The results obtained show that the band offsets vary with the composition of the (GeTe)x(Sb2Te3)1−x alloy, exhibiting a parabolic dependence on the amount of GeTe in the alloy. Increasing the proportion of GeTe in the (GeTe)x(Sb2Te3)1−x alloy was generally found to increase (decrease) the valence band (conduction band) offsets, while the binary alloys (GeTe, Sb2Te3) have similar band offset values. This information could be useful for phase change memory device design and optimization.
Effect of Mn substituents on the domain and local structures of Na1/2Bi1/2TiO3–BaTiO3 single crystals near a morphotropic phase boundary
Authors: Yao Jianjun , Yang Yaodong , Monsegue Niven , Li Yanxi , Li Jiefang , Zhang Qinhui , Ge Wenwei , Luo Haosu , Viehland D.
Published: March 2011

The ferroelectric domain and local structures of Na1/2Bi1/2TiO3-x%BaTiO3 (NBT-BT) and 0.14 at. %Mn substituted Na1/2Bi1/2TiO3-x%BaTiO3 (Mn:NBT-BT) single crystals with x=5.5 near a morphotropic phase boundary have been investigated by transmission electron microscopy. Increased ferroelectric ordering and enhanced in-plane octahedral tilting were observed for Mn:NBT-BT compared with NBT-BT. Bragg-filtered lattice images revealed that the size of the in-phase tilt domains of Mn:NBT-BT were on the order of 2 to 8 nm, with a tendency of alignment along {110}.
Plasma confinement by hemispherical cavity in laser-induced breakdown spectroscopy
Authors: Guo L. B. , Li C. M. , Hu W. , Zhou Y. S. , Zhang B. Y. , Cai Z. X. , Zeng X. Y. , Lu Y. F.
Published: March 2011

An aluminum hemispherical cavity (diameter: 11.1 mm) was used to confine plasmas produced by a KrF excimer laser in air from a steel target with a low concentration manganese in laser-induced breakdown spectroscopy. A significant enhancement (factor >12) in the emission intensity of Mn lines was observed at a laser fluence of 7.8 J/cm2 when the plasma was confined by the hemispherical cavity, leading to an increase in plasma temperature about 3600 K. The maximum emission enhancement increased with increasing laser fluence. The spatial confinement mechanism was discussed using shock wave theory.
Thermodynamics of multiferroic BiFeO3: Applications for the deposition of BiFeO3 thin films
Authors: Mei Zhi-Gang , Shang ShunLi , Wang Yi , Liu Zi-Kui
Published: March 2011

The formation enthalpy of BiFeO3 from oxides is studied by density-functional theory. It is predicted to be a small negative value by local density approximation plus U calculations, which is used to study the phase equilibria and chemical potential-temperature phase diagram of BiFeO3 by the calculation of phase diagram approach. The predicted processing window for BiFeO3 agrees well with experimental oxygen partial pressure-temperature conditions. We further predict that Bi chemical potential represented by its partial pressure can be used to adjust the stability window of BiFeO3. This opens another dimension in tailoring processing conditions for optimal growth of BiFeO3 films.
Design Codes, Opportunity Space, and the Marketability of New Housing
Authors: Adams David , Croudace Robert , Tiesdell Steve
Published: March 2011

This paper is about state — market relations in speculative housebuilding, with specific reference to the means by which higher quality design can be achieved in new residential developments. Applying the concept of opportunity space, we investigate the extent to which form-based/design codes change developers' opportunity space both in absolute terms and vis-à-vis the opportunity space of designers. We interrogate this using evidence from a major design-coded residential development in the southeast of England, drawing on interviews with housebuilders. We conclude that design codes have the potential to transform the market context for new housebuilding, but that the typical housebuilder has yet to be convinced of their business advantages.
Autochthonous Streptomyces regulate the metabolism of seedlings of Araucaria angustifolia (Coniferales) during root colonisation
Authors: Dalmas F. R. , Pereira T. C. B. , Bogo M. R. , Astarita L. V.
Published: March 2011

Araucaria angustifolia (Bertol.) Kuntze, known as Brazilian pine, is an endangered species of great ecological and economic importance. This species grows slowly and unevenly, with high mortality in commercial plantations. Streptomyces is a genus of soil microorganisms that may have a beneficial effect on plant growth. This study evaluated the effect of three autochthonous Streptomyces spp. isolates (PM1, PM4 and PM9) on the initial metabolism and development of A. angustifolia seedlings. The enzymatic activity of phenylalanine ammonia-lyase, polyphenol oxidase and peroxidase, and the levels of phenolic compounds, flavonoids and chlorophyll were determined in extracts from roots and leaves of the seedlings. Assays were carried out 1, 3 and 9 days after the roots were inoculated with each isolate. Length and fresh mass of shoots and roots as well as the volume and density of roots were evaluated at 100 days after seedling inoculation. All the Streptomyces spp. showed rhizospheric competence and produced auxin. The activities of polyphenol oxidase and peroxidase exhibited a tissue-temporal regulation in the presence of the isolates. Levels of phenolics, flavonoids and chlorophylls did not change in the period analysed. The root system of seedlings inoculated with all isolates was shorter and denser, with a small volume. The PM9 isolate promoted shoot growth and affected plant metabolism, proving to be a promising rhizobacterium with a plant growth-promoting rhizobacteria role.
New records of leaf galls and arthropod oviposition scars in Permian - Triassic Gondwanan gymnosperms
Authors: McLoughlin Stephen
Published: March 2011

Single, midrib-positioned galls and midrib-flanking oviposition scars are described from four species of Permian glossopterid foliage from Australia and South Africa. Several of these traces have been mistaken previously for glossopterid reproductive organs or fructification detachment scars. A single Early Triassic corystosperm leaf from Australia is reported bearing multiple disc-like galls on both the midrib and pinnules. A Middle Triassic taeniopterid gymnosperm leaf from Australia is described hosting oviposition scars between consecutive secondary veins flanking the midrib. These fossils attest to a much richer record of plant–arthropod interactions in the late Palaeozoic and early Mesozoic of high-latitude Gondwana than previously reported, and indicate that herbivory and reproductive strategies involving galling and foliar ovipositioning were re-established relatively soon after the end-Permian mass extinction event that saw major turnovers in both the flora and insect fauna.
Fire-patterned vegetation and the development of organic soils in the lowland vegetation mosaics of south-west Tasmania
Authors: Wood S. W. , Hua Q. , Bowman D. M. J. S.
Published: March 2011

Two contrasting ecological models have been proposed for the forest–moorland vegetation mosaics of south-west Tasmania that stress different interactions between fire, soils, vegetation and the physical environment to produce either stable or dynamic vegetation patterns. We investigated aspects of these models by sampling organic soil profiles across vegetation mosaics to determine variation in soil depth, organic carbon (C) content, nutrient capital, stable C isotope composition (δ13C) and 14C radiocarbon age in two contrasting landscape settings. 14C basal ages of organic soils ranged from recent (<400 calibrated (cal.) years BP) to mid Holocene (~7200 cal. years BP), with a tendency for older soils to be from poorly drained moorlands and younger soils from the forest. The long-term net rate of C accumulation ranged from 2.7 to 19.2 gC m–2 year–1, which is low compared with northern hemisphere peatland systems. We found that δ13C in organic soil profiles cannot be used to infer Holocene vegetation boundary dynamics in these systems. We found a systematic decrease of phosphorus from rainforest through eucalypt to moorland, but estimated that phosphorus capital in moorland soils was still sufficient for the development of forest vegetation. Our results suggest that the characteristics of organic soils across the landscape are the result of interactions between not only vegetation and fire frequency, but also other factors such as drainage and topography.
The genetic variation in the timing of heteroblastic transition in Eucalyptus globulus is stable across environments
Authors: Hamilton M. G. , Tilyard P. A. , Williams D. R. , Vaillancourt R. E. , Wardlaw T. J. , Potts B. M.
Published: March 2011

Eucalyptus globulus is one of the best known examples of a heteroblastic plant. It exhibits a dramatic phase change from distinctive juvenile to adult leaves, but the timing of this transition varies markedly. We examined the genetic variation in the timing of heteroblastic transition using five large open-pollinated progeny trials established in north-western Tasmania. We used univariate and multi-variate mixed models to analyse data on the presence/absence of adult or intermediate foliage at age 2 years from a total of 14 860 trees across five trials, as well as height to heteroblastic phase change from one trial. Up to 566 families and 15 geographic subraces of E. globulus were represented in the trials. The timing of the heteroblastic transition was genetically variable and under strong genetic control at the subrace and within-subrace level, with single-trial narrow-sense heritability estimates for the binary trait averaging 0.50 (range 0.44–0.65). The degree of quantitative trait differentiation in the timing of heteroblastic transition among subraces, as measured by QST, exceeded the published level of neutral molecular marker (FST) differentiation in all cases, arguing that diversifying selection has contributed to shaping broad-scale patterns of genetic differentiation. Most inter-trial genetic correlations were close to one at the subrace and additive genetic levels, indicating that the genetic variation in this important developmental change is expressed in a stable manner and that genotype-by-environment interaction is minimal across the environments studied.
Defining entities in the Acacia saligna (Fabaceae) species complex using a population genetics approach
Authors: Millar M. A. , Byrne M. , O'Sullivan W.
Published: March 2011

Traditional morphological taxonomic classification is problematic in the Acacia saligna (Labill.) H.L.Wendl. species complex. Reliable identification of entities within the species is essential due to its extensive use both in Australia and overseas, its propensity for weediness, and its ongoing development for use in agroforestry. We used a Bayesian analysis approach to assess genetic structure in populations across the species natural range and to define the natural distributions of various genetic entities. The results indicate that three highly divergent genetic entities are apparent in the A. saligna species complex with further fine-scale genetic subdivision present within two. The three primary genetic entities correspond to the informally described subsp. ‘saligna’ and subsp. ‘pruinescens’ combined, subsp. ‘stolonifera’, and subsp. ‘lindleyi’. Within this primary structure two further entities are apparent; one separating subsp. ‘saligna’/‘pruinescens’ into eastern and western populations and the other distinguishing north-western ‘lindleyi’ populations from the rest of that subspecies distribution. The north-western catchments may have been an important refugium for the species diversity. The results of the study will aid in breeding programs, conservation of natural populations and control of invasive populations of this taxon.
Arbuscular mycorrhizas enhance plant interception of leached nutrients
Authors: Asghari Hamid Reza , Cavagnaro Timothy Richard
Published: March 2011

Arbuscular mycorrhizal fungi (AMF) can increase plant growth and nutrition. However, their capacity to reduce the leaching of nutrients through the soil profile is less well understood. Here we present results of an experiment in which the effects of forming arbuscular mycorrhizas (AM) on plant growth and nutrition, nutrient depletion from soil, and nutrient leaching, were investigated in microcosms containing the grass Phalaris aquatica L. Mycorrhizal and non-mycorrhizal plants were grown in a mixture of riparian soil and sand under glasshouse conditions. The formation of AM by P. aquatica significantly increased plant growth and nutrient uptake. Lower levels of NO3–, NH4+ and plant available P in both soil and leachate were observed in columns containing mycorrhizal root systems. These differences in nutrient interception were proportionally greater than the increase in root biomass of the mycorrhizal plants, compared with their non-mycorrhizal counterparts. Taken together, these data indicate that mycorrhizal root systems have an important, but previously little considered, role to play reducing the net loss of nutrients via leaching.
Anatomical and chemical characteristics of culm of rice brittle mutant bc7(t)
Authors: Wei Cunxu , Xie Peisong , Chen Yifang , Yu Huaguang , Su Yanjing , Gu Minghong , Yan Changjie
Published: March 2011

Brittleness culm is an important agronomic trait that has a potential usefulness in agricultural activity as animal forage. In the present study, the anatomy of culm of rice (Oryza sativa L.) brittle mutant bc7(t) was investigated with light microscopy and electron microscopy. Findings showed bc7(t) exhibited higher area percentages of mechanical and conducting tissues, and lower cell wall thickness of sclerenchyma cells. Chemical analyses and 13C CP/MAS NMR spectra of cell walls indicated that the content of cellulose decreased, and the contents of hemicellulose, lignin and silicon was increased in bc7(t). Lignin histochemical staining and cytochemical localisation revealed that the higher lignin was localised in epidermal, sclerenchyma and vascular bundle cells in bc7(t). The energy dispersive X-ray microanalysis showed that the contents of silicon were higher in bc7(t) than in the wild type. These results indicate that cellulose, hemicellulose, lignin, silicon and the area percentages of mechanical and conducting tissues could be regulated in a compensatory fashion, possibly contributing to metabolic flexibility and a growth advantage to sustain the bc7(t) normal growth habit like the wild-type plant.
Slope effect on laboratory fire spread: contribution of radiation and convection to fuel bed preheating
Authors: Dupuy J.-L. , Maréchal J.
Published: March 2011

Two series of 16 and 18 laboratory fire experiments were conducted to explore the respective roles of radiation and convection heat transfer in slope effect on fire spread. The first series attempts to measure fuel temperature and gas temperature simultaneously and at the same location using an infrared camera and thermocouples respectively. The second series measures the incident radiant heat flux as would be received by a small fuel bed volume ahead of the fire line. These measurements are used to compute a fuel bed heat balance for each slope angle (0°, 10°, 20° and 30°). Overall, radiative heating is found to be the heat transfer mechanism that dominates in the slope effect between 0° and 20°, but close to the fire line (<10 cm), the flux due to convective heating is also significant, reaching one-third of the net heat flux at a 20° slope angle. When the slope angle increases from 20° to 30°, the rate of spread rises by a factor of 2.5 due to a marked increase in convective heating, while radiative heating no longer increases. Far from the fire line, cooling by convection is found to be substantial except at the 30° slope angle.
Users as essential contributors to spatial cyberinfrastructures
Authors: Poore Barbara S.
Published: March 2011

Current accounts of spatial cyberinfrastructure development tend to overemphasize technologies to the neglect of critical social and cultural issues on which adoption depends. Spatial cyberinfrastructures will have a higher chance of success if users of many types, including nonprofessionals, are made central to the development process. Recent studies in the history of infrastructures reveal key turning points and issues that should be considered in the development of spatial cyberinfrastructure projects. These studies highlight the importance of adopting qualitative research methods to learn how users work with data and digital tools, and how user communities form. The author's empirical research on data sharing networks in the Pacific Northwest salmon crisis at the turn of the 21st century demonstrates that ordinary citizens can contribute critical local knowledge to global databases and should be considered in the design and construction of spatial cyberinfrastructures.