bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical properties of normal spinel MxCo3−xO4(M=CrandCu): Coexistence of charge-transfer and crystal-field transitions
Authors: Kim Kwang Joo , Park Young Ran , Hyun Dong Hoon , Lee Sung Ho
Published: August 2004

Optical properties of normal spinel MxCo3−xO4(M=CrandCu) films grown by sol-gel method have been investigated by the spectroscopic ellipsometry (SE) in the 1.5–4eV region. For x<1.0, the cubic lattice constant of CrxCo3−xO4 is found to increase linearly with x while that of CuxCo3−xO4 decreases slightly. By comparing the optical constants of the ternary oxides measured by SE with those of Co3O4, Mott-Hubbard, charge-transfer (CT) and crystal-field (CF) transitions are found to coexist in the same energy region. The changes in the optical absorption spectrum by Cr and Cu alloying into Co3O4 are explained in terms of the changes in the electronic structure of Co3O4 through the substitution of the octahedral Co3+ and the tetrahedral Co2+ sites of the spinel structure by Cr3+ and Cu2+ ions, respectively. The CT transitions are explained in terms of d states of the Co3+ and Co2+ ions and p states of O2− ion. The CF transitions are interpreted as originating from the CF multiplets of the octahedral Co3+ and Cr3+ ions.
Electron-stimulated reactions in thin D2O films on Pt(111) mediated by electron trapping
Authors: Petrik Nikolay G. , Kimmel Greg A.
Published: August 2004

We have measured the electron-stimulated desorption (ESD) of D2, O2, and D2O, the electron-stimulated dissociation of D2O at the D2O/Pt interface, and the total electron-stimulated sputtering in thin D2O films adsorbed on Pt(111) as a function of the D2O coverage (i.e., film thickness). Qualitatively different behavior is observed above and below a threshold coverage of ∼2 monolayers (ML). For coverages less than ∼2 ML electron irradiation results in D2O ESD and some D2 ESD, but no detectible reactions at the water/Pt interface and no O2 ESD. For larger coverages, electron-stimulated reactions at the water/Pt interface occur, O2 is produced and the total electron-stimulated sputtering of the film increases. An important step in the electron-stimulated reactions is the reaction between water ions (generated by the incident electrons) and electrons trapped in the water films to form dissociative neutral molecules. However, the electron trapping depends sensitively on the water coverage: For coverages less than ∼2 ML, the electron trapping probability is low and the electrons trap preferentially at the water/vacuum interface. For larger coverages, the electron trapping increases and the electrons are trapped in the bulk of the film. We propose that the coverage dependence of the trapped electrons is responsible for the observed coverage dependence of the electron-stimulated reactions.
Electron-stimulated production of molecular hydrogen at the interfaces of amorphous solid water films on Pt(111)
Authors: Petrik Nikolay G. , Kimmel Greg A.
Published: August 2004

The electron-stimulated production of molecular hydrogen (D2, HD, and H2) from amorphous solid water (ASW) deposited on Pt(111) is investigated. Experiments with isotopically layered films of H2O and D2O are used to profile the spatial distribution of the electron-stimulated reactions leading to hydrogen within the water films. The molecular hydrogen yield has two components that have distinct reaction kinetics due to reactions that occur at the ASW/Pt interface and the ASW/vacuum interface, but not in the bulk. However, the molecular hydrogen yield as a function of the ASW film thickness in both pure and isotopically layered films indicates that the energy for the reactions is absorbed in the bulk of the films and electronic excitations migrate to the interfaces where they drive the reactions.
Experimental studies of the dynamics of the bond-forming reactions of CF22+ with H2O using position-sensitive coincidence spectroscopy
Authors: Harper Sarah M. , Hu Sunny W.-P. , Price Stephen D.
Published: August 2004

The dynamics of the product channels forming OCF++H++HF and HCF2++H++O following the collisions of CF22+ with H2O have been investigated with a new position-sensitive coincidence experiment at a center-of-mass collision energy of 5.6 eV. The results show the formation of OCF+ occurs via the formation of a doubly charged collision complex [H2O-CF2]2+ which subsequently undergoes a charge separating dissociation to form H+ and HOCF2+. The HOCF2+ monocation subsequently fragments to form HF+OCF+. The lifetimes of the collision complex and the HOCF2+ ion are at least of the order of their rotational period. The kinetic energy release in this reaction indicates that it involves the ground state of CF22+ and forms the ground electronic states of OCF+ and HF. The mechanism for forming HCF2+ involves the direct and rapid abstraction of a hydride ion from H2O by CF22+. The resulting OH+ ion subsequently fragments to H++O, on a time scale at least comparable with its rotational period.
Effects of varying interfacial oxide and high-k layer thicknesses for HfO2 metal–oxide–semiconductor field effect transistor
Authors: Rhee Se Jong , Kang Chang Yong , Kang Chang Seok , Choi Rino , Choi Chang Hwan , Akbar Mohammad S. , Lee Jack C.
Published: August 2004

A metal–oxide–semiconductor capacitor and field effect transistor with a hafnium oxide (HfO2) dielectric have been fabricated. Various thicknesses of interfacial oxide and HfO2 film have been used. The results show that the flatband voltage changed due to the change in the physical thickness of the HfO2 film, and not that of the interfacial oxide layer. In addition, the effective channel electron mobility depends on both the amount of fixed charges and the distance from the fixed charges to the Si surface. The results also suggest that the fixed charges are rather uniformly distributed throughout the bulk of high-k layer.
Small angle x-ray scattering metrology for sidewall angle and cross section of nanometer scale line gratings
Authors: Hu Tengjiao , Jones Ronald L. , Wu Wen-li , Lin Eric K. , Lin Qinghuang , Keane Denis , Weigand Steve , Quintana John
Published: August 2004

High-volume fabrication of nanostructures requires nondestructive metrologies capable of measuring not only the pattern size but also the pattern shape profile. Measurement tool requirements will become more stringent as the feature size approaches 50nm and tolerances of pattern shape will reach a few nanometers. A small angle x-ray scattering (SAXS) based technique has been demonstrated to have the capability of characterizing the average pitch size and pattern width to subnanometer precision. In this study, we report a simple, modeling-free protocol to extract cross-section information such as the average sidewall angle and the pattern height of line grating patterns from the SAXS data. Diffraction peak intensities and reciprocal space positions are measured while the sample is rotated around the axis perpendicular to the grating direction. Linear extrapolations of peak positions in reciprocal space allow a precise determination of both the sidewall angle and the pattern height.
Study on the mechanism of the squeeze-strengthen effect in magnetorheological fluids
Authors: Zhang X. Z. , Gong X. L. , Zhang P. Q. , Wang Q. M.
Published: August 2004

Current magnetorheological (MR) fluids have the limitation that their yield stresses are not strong enough to meet some industrial requirements. X. Táng, X. Zhang, and R. Tao [J. App. Phys 87, 2634 (2000)] proposed a method to achieve high-efficiency MR fluids by study of squeeze-strengthen effect. But there is little report on its mechanism. This paper aims to investigate this effect through experimental and theoretical approaches. For this purpose, an apparatus is designed to experimentally study the mechanism of this squeeze-strengthen effect. Taking account of a modified magnetic dipole model and the friction effect, a semiempirical model is proposed to explain this effect. In addition, this model is expected to study the squeeze-strengthen effect in electrorheological fluids.
Suppression of silicidation in polycrystalline-Si/ high-κ insulator/SiO2∕Si structure by helium through process
Authors: Muraoka Kouichi
Published: August 2004

Suppression of silicidation in polycrystalline-Si (poly-Si)/ high-κ insulators (ZrO2,HfO2)∕SiO2∕Si structure by helium (He) through process which adds He gas during a poly-Si gate process was demonstrated. In Si deposition on ZrO2 and HfO2 by SiH4 flow diluted by N2 or He, surface silicidation can be suppressed by lowering of initial deposition temperature below 600 and 650°C, respectively, but thin SiO2 films are formed between Si films and these high-κ insulator surfaces without being dependent on the dilution gases. Moreover, it is found that He through process of low-temperature SiH4 flow diluted by He and high-pressure He postannealing is the most effective means of suppressing not only the thermal degradation of high-κ insulator/SiO2∕Si interface but also the silicidation of poly-Si∕SiO2/ high-κ insulator interface, whereas conventional N2 through process cannot suppress both. These results mean that high-concentration He atoms are indispensable for upper and lower SiO2∕Si interfaces. It is supposed that many He atoms physically obstruct SiO creation through the quenching of atomic vibration at both SiO2∕Si interfaces, thus impeding the first step of silicidation reaction. In addition, by comparing with SiO2 single film, it is found that the suppression efficiency of He atoms in the high-κ insulator/SiO2∕Si system is higher than that in the SiO2∕Si system. This phenomenon can be rationalized by presupposing that the efficiency reflected the degradation-prone site density in the interfacial SiO2 layer.
Comparative study of photoluminescence of undoped and erbium-doped size-controlled nanocrystalline Si∕SiO2 multilayered structures
Authors: Timoshenko V. Yu. , Lisachenko M. G. , Shalygina O. A. , Kamenev B. V. , Zhigunov D. M. , Teterukov S. A. , Kashkarov P. K. , Heitmann J. , Schmidt M. , Zacharias M.
Published: August 2004

Spectra and transients of the photoluminescence (PL) of undoped and Er-doped size-controlled nanocrystalline Si∕SiO2 multilayered structures with mean nanocrystal size of 1.5–4.5nm have been comparatively investigated. The Er-doped structures exhibit a strong Er-related PL band at 0.81eV, while the efficiency of the intrinsic PL band of Si nanocrystals at 1.2–1.7eV decreases by several orders of magnitude in comparison with the undoped structures. At low temperature the PL spectra of the Er-doped structures show several dips separated by the energy of Si TO-phonon and bound to the transition energies between the second and third excited states to the ground state of Er3+. The Er-related PL is characterized by lifetimes of around 3–5ms, a weak temperature quenching, and a high efficiency, which is comparable or even stronger than that of the intrinsic PL in the corresponding undoped samples. This efficient sensitizing of the Er-related luminescence is explained by the structural properties of the samples, which favor a strong coupling between the excitons confined in Si nanocrystals and upper excited states of the Er3+ ions in the SiO2 matrix.
Simulations studies on influence of He concentration on discharge of alternating current plasma display panels in He-Ne-Xe mixture
Authors: Lee Insook , Choi K. Y.
Published: August 2004

With recent experiments to add He gas to the conventional Ne-Xe discharge gas mixture for high luminous efficiency plasma display panels, we have performed simulations on a coplanar structured alternating current plasma display panel sustained in the He-Ne-Xe gas mixture, by using the two-dimensional fluid model simulator. As the He concentration increases, luminance and luminous efficiencies increase but power consumption decreases, which agrees well with the recent experimental findings. He atoms increase the number of Xe*(P23) in the excited state and thus, the dimer emission is increased while the resonant line is reduced with the He content. As a result, the total vacuum ultraviolet emission is increased and higher luminance and higher luminous efficiency can be obtained. The enhanced mobilities of the ions in the gas mixture by adding He gas to the mixture also play an important role in increasing luminous efficiency.
Liquid–crystal phase diagrams of binary mixtures of hard spherocylinders
Authors: Cinacchi Giorgio , Mederos Luis , Velasco Enrique
Published: August 2004

We have built the liquid crystal phase diagram of several binary mixtures of freely rotating hard spherocylinders employing a second-order virial density functional theory with Parsons scaling, suitably generalized to deal with mixtures and smectic phases. The components have the same diameter and aspect ratio of moderate value, typical of many mesogens. Attention has been paid to smectic–smectic demixing and the types of arrangement that rods can adopt in layered phases. Results are shown to depend on the aspect ratio of the individual components and on the ratio of their lengths. Smectic phases are seen not to easily mix together at sufficiently high pressures. Layered phases where the longer rods are the majority component have a smectic-A structure. In the opposite case, a smectic-A2 phase is obtained where the shorter particles populate the layers and the longer ones prefer to stay parallel to the latter in the interlayer region.
High-field magnetoresistance of Fe∕GaAs∕Fe tunnel junctions
Authors: Zenger M. , Moser J. , Wegscheider W. , Weiss D. , Dietl T.
Published: August 2004

We investigate transport through 6–10nm thin epitaxial GaAs(001) barriers sandwiched between polycrystalline iron films. Apart from a pronounced tunneling magnetoresistance effect at low magnetic fields, we observe a distinct negative magnetoresistance (MR) at low and a positive MR at higher temperatures. We show that the negative MR contribution is only observed for the ferromagnetic iron contacts but is absent if iron is replaced by copper or gold electrodes. Possible explanations of the negative MR involve suppression of spin-flip scattering or Zeeman splitting of the tunneling barrier, but neither of these explanations is fully consistent with the data.
Influence of grain size on the electronic and the magnetic properties of La0.7Ca0.3MnO3−δ
Authors: Park J. S. , Kim C. O. , Lee Y. P. , Lee Y. S. , Shin H. J. , Han H. , Lee B. W.
Published: August 2004

Polycrystalline La0.7Ca0.3MnO3−δ (LCMO), prepared by a solid-state reaction, was annealed at different temperatures TA. The variation of TA was responsible for observed changes in the physical properties, including a shift in the metal-insulator transition temperature, which is explained by variation in the oxygen content. At low temperatures the magnetization of LCMO samples was also observed to be dependent on TA. A reduction of the grain boundaries leads to enhancement of both the magnetization and the sensitivity for low-field magnetoresistance. By using Mn L3-edge x-ray absorption, it was also found that the Mn3+∕Mn4+ ratio increases with the grain size, and that the oxygen content in LCMO is governed by the grain boundaries.
Kinetic pathways of sheared block copolymer systems derived from Minkowski functionals
Authors: Sevink G. J. A. , Zvelindovsky A. V.
Published: August 2004

We employ Minkowski functionals to analyze the kinetics of pattern formation under an applied external shear flow. The considered pattern formation model describes the dynamics of phase separating block copolymer systems. For our purpose, we have chosen two block copolymer systems (a melt and a solution) that exhibit a hexagonal cylindrical morphology as an equilibrium structure. Our main objective is the determination of efficient choices for the treshold values that are required for the calculation of the Minkowski functionals. We find that a minimal set of two treshold values (one from which should be equal to an average density value and another to a higher density value) is sufficient to unraffle the phase separation kinetics. Given these choices, we focus on the influence of the degree of phase separation, and the instance at which the shear is applied, on the kinetic pathways. We also found a remarkable similarity of the time evolution of Euler characteristic and the segregation parameter for the average density choice.
Molecular dynamics investigation of a density-driven glass transition in a liquid crystal system
Authors: Vieira Pablo A. , Lacks Daniel J.
Published: August 2004

Molecular dynamics simulations are carried out to address the density-driven glass transition in a system of rodlike particles that interact with the Gay–Berne potential. Since crystallization occurs in this system on the time scale of the simulations, direct simulation of the glass transition is not possible. Instead, glasses with isotropic orientational order are heated to a temperature T, and the relaxation times by which nematic orientational order develops are determined. These relaxation times appear to diverge at a critical density ρc; i.e., the system can equilibrate at ρ<ρc, but it cannot equilibrate at ρ>ρc (at the temperature T). The relaxation times follow a power-law scaling as the critical density is approached, suggesting that this density-driven glass transition concurs with mode coupling theory.
Method of determining the wall conductivity of a multimode microwave applicator
Authors: Gold S. H. , Fliflet A. W. , Lewis D. , Bruce R. W. , Zharova N. A. , Semenov V. E.
Published: August 2004

We present results for the estimation of the effective surface conductivity of the walls of a multimode microwave cavity applicator, based on measurements of reflected power from the cavity. During microwave thermal processing, this conductivity is a critical issue because the walls of the microwave applicator can become contaminated with evaporated material or process by-products, resulting in significantly reduced surface reflectivity from that of the bare metal. Thus, the cavity walls may absorb an increased amount of microwave energy, compared to that expected based on reflectivity data for clean metallic walls. A method based on the expansion of the total microwave fields in eigenmodes of a cylindrical waveguide is used to find the power reflection coefficient from an overmoded cylindrical applicator cavity as a function of the wall conductivity. The results of this analysis are compared with power reflection measurements from an experimental multimode applicator cavity, in order to determine a realistic value for the cavity wall loss. Because of the sensitivity of the calculated reflection spectrum to small changes in cavity geometry, a detailed comparison of the calculated reflectivity with that measured is not practical. It is found instead that a comparison of the average reflectivity over a broad frequency interval containing many cavity resonances, combined with a calculation of microwave reflectivity as a function of surface reflectivity, is the best means of determining the effective conductivity (effective surface reflectivity) of the walls of a multimode cavity applicator. The realistic surface conductivities and cavity wall loss determined by this means can be used for modeling and optimization of microwave material processing. A comparison is also shown of the calculated contours of microwave power density in the cavity with experimental measurements using thermal paper, showing reasonable agreement. This is done for various transverse and circumferential sections in the cavity and demonstrates the potential and limitations of this technique for characterizing power distributions in microwave systems. The nonlinear response of the thermal paper complicates interpretation, but image analysis techniques could extract substantial amounts of more detailed information from the thermal paper results with suitable calibration techniques.
Real time quantum propagation on a Monte Carlo trajectory guided grids of coupled coherent states: 26D simulation of pyrazine absorption spectrum
Authors: Shalashilin Dmitrii V. , Child Mark S.
Published: August 2004

In this work we apply the coupled coherent states technique of quantum molecular dynamics to simulation of the absorption spectrum of pyrazine. All 24 vibrational modes are taken into account. The nonadiabatic coupling obetween the S1 and S2 electronic states is treated by a mapping approach that adds two extra degrees of freedom to the effective vibronic Hamiltonian. The results are in a good agreement with experiment and with previous calculations by quantum multiconfigurational time dependent Hartree and semiclassical Herman-Kluk methods.
Organic light-emitting diodes based on a blend of poly[2-(2-ethylhexyloxy)-5-methoxy-1,4-phenylenevinylene] and an electron transporting material
Authors: Ahn J. H. , Wang C. , Pearson C. , Bryce M. R. , Petty M. C.
Published: August 2004

Organic light-emitting devices (OLEDs) containing a blend of poly[2-(2-ethylhexyloxy)-5-methoxy-1,4-phenylenevinylene] (MEH-PPV) and an electron transporting material, 2,7-bis[2-(4-tert-butylphenyl)-1,3,4-oxadiazol-5-yl]-9,9-dihexylfluorene have been fabricated. The external quantum efficiencies of the OLEDs containing the electron transport compound were increased significantly over those obtained for devices based only on MEH-PPV. For example, the efficiency for a device incorporating 95% of electron transport compound was two orders of magnitude greater than that for a nonblended device. In all of our investigations, the electroluminescence (orange/yellow emission) originated exclusively from the MEH-PPV material, even for very high concentrations (>90%) of the electron transport component.
Stimulated Raman scattering of a laser beam in a plasma with azimuthal magnetic field
Authors: Sajal Vivek , Tripathi V. K.
Published: August 2004

A strong azimuthal magnetic field localizes the lower hybrid waves radially in laser produced plasmas. The laser pump parametrically excites a lower hybrid wave and a backscattered electromagnetic sideband wave. The density perturbation due to the lower hybrid wave couples with the oscillatory velocity of electrons due to the pump wave, to produce a nonlinear current driving the sideband. The pump and sideband waves exert a ponderomotive force on electrons driving the lower hybrid wave. The local effects reduce the growth rate of stimulated Raman scattering. The fundamental radial eigenmode (p=0) of the lower hybrid wave is the maximally growing mode. The scattering process can be used as a diagnostic for the azimuthal magnetic field.
Effects of electron inertia in capacitively coupled radio frequency discharges
Authors: Xiang Nong
Published: August 2004

The effects of the electron inertia on the plasma and sheath dynamics in capacitively coupled rf discharges with frequency ωωpi are investigated (here, ω and ωpi are the rf frequency and bulk ion plasma frequency, respectively). It is found that the effects of the electron inertia on the plasma density and ion velocity in the quasi-neutral region depend on the ratio of the amplitudes of the discharge current Irf and ion current IB=en0Cs (here, e is the unit charge, n0 is the plasma density at center, and Cs is the ion sound speed). If the ratio is small so that Irf/IBmi/me (here, mi and me are ion and electron masses, respectively), the ion and time-averaged electron densities, ion velocity, and electric fields are little affected by the electron inertia. Otherwise, the effects of the electron inertia are significant. It is also shown that the assumption that the electrons obey the Boltzmann distribution in the sheath is invalid when the electron flux flowing to the electrode is significant.
Solid-state power supply for gas lasers
Authors: Bertolini A. , Beverini N. , Carelli G. , Francesconi M. , Nannizzi M. , Strumia F. , Ioli N. , Moretti A.
Published: August 2004

A novel pulsed power supply for gas lasers is presented. The device uses only solid state components and is based on a capacitor bank discharge. Fast switching of the discharge is triggered by an insulated gate bipolar transistor. The terminal section of the power supply is a transformer designed to match the reactive capacitance of a gas discharge. Strokes up to 30 kV and 30 mA are achieved across the secondary windings of this transformer. The power supply delivers high voltage pulses with a duration between 0.5 and 50 μs and a repetition rate up to some kHz. The power supply has been tested on a longitudinal discharge quasi-cw regime CO2 laser. Laser pulses were generated with a duration down to the microseconds region, a peak power exceeding some kilowatts, and a repetition rate ranging from 200 Hz to a few kHz.
The combined effects of magnetic field and magnetic field gradients on convection in crystal growth
Authors: Qi Jianwei , Wakayama Nobuko I.
Published: August 2004

The effect of an external magnetic field on convection in crystal growth is investigated numerically. The geometry considered is a cylindrical vessel filled with crystal solutions. The vessel partially heated from below is placed outside or inside a superconducting magnet. Numerical simulations show that the convection can be suppressed or promoted mainly due to the location of the vessel in the magnet. When the vessel is located above the center of the magnet, the convection is reduced more greatly than that at the center of the magnet. However, when the vessel is located below the center of the magnet, the convection is greater than that at the center of the magnet and that outside the magnet in absence of the field. The above results demonstrate that both magnetic effects on convection in solution will occur due to the magnetic field and its gradient. Generally, the magnetic field will induce the Lorentz force to damp the convection when the solution is electrically conducting. On the other hand, the magnetic field gradient resulted from the inhomogeneity of the field will produce the magnetization force and the magnetic buoyancy to suppress or promote the convection when the vertical magnetization force is opposite to or the same as the gravity. The above results can qualitatively explain recent experimental findings in protein crystal growth and show the potential of using both the magnetic field and field gradient to control convection in nonconducting or low conducting solutions, especially in the process of crystal growth from aqueous solutions.
Effect of thermal excitation on intermolecular charge transfer efficiency in conducting polyaniline
Authors: Li Guofeng , Josowicz Mira , Janata Jiří , Semancik Steve
Published: August 2004

A conductometric gas-sensing platform with temperature control has been adopted to probe temperature-dependent phenomena in conducting polymers. This letter describes our recent observation of thermal effects on the intermolecular charge transfer efficiency of conducting polyaniline at both ends of the charge transfer—either as a donor or as an acceptor, upon exposure to gaseous analytes. When polyaniline is serving as a donor, the thermal excitation of electrons in polyaniline facilitates the charge transfer. However, if polyaniline assumes the role of an acceptor, the charge transfer becomes less efficient at higher temperatures. Furthermore, a simplified band structure model is employed to elucidate such discriminative behavior.
Variable-focus liquid lens for miniature cameras
Authors: Kuiper S. , Hendriks B. H. W.
Published: August 2004

The meniscus between two immiscible liquids can be used as an optical lens. A change in curvature of this meniscus by electrowetting leads to a change in focal distance. It is demonstrated that two liquids in a tube form a self-centered lens with a high optical quality. The motion of the lens during a focusing action was studied by observation through the transparent tube wall. Finally, a miniature achromatic camera module was designed and constructed based on this adjustable lens, showing that it is excellently suited for use in portable applications.
Dielectric characteristics of nanocrystalline Ag–Ba0.5Sr0.5TiO3 composite thin films
Authors: Jayadevan K. P. , Liu C. Y. , Tseng T. Y.
Published: August 2004

Nanocrystalline Ag–Ba0.5Sr0.5TiO3 (Ag–BST) composite thin films are deposited on Pt/Ti/SiO2/Si substrates by a sol-gel method. The voltage-dependent capacitance (C–V) and dielectric loss of the films decrease with increasing Ag up to 2mol% due to a series configuration involving low dielectric interface layers and dense microstructures. The evidence for asymmetric distribution of charge carriers in the Ag–BST film is derived from C–V measurements. The dielectric tunability of BST film with 1mol% Ag is comparable to that of pure BST.
Femtosecond-irradiation-induced refractive-index changes and channel waveguiding in bulk Ti3+:Sapphire
Authors: Apostolopoulos V. , Laversenne L. , Colomb T. , Depeursinge C. , Salathé R. P. , Pollnau M. , Osellame R. , Cerullo G. , Laporta P.
Published: August 2004

We have employed femtosecond laser writing in order to induce refractive-index changes and waveguides in Ti3+-doped sapphire. Doping the sapphire crystal with an appropriate ion significantly reduces the threshold for creating structural changes, thus enabling the writing of waveguide structures. Passive and active buried channel waveguiding is demonstrated and images of the guided modes, propagation-loss values, fluorescence spectra, and output efficiencies are presented. The guiding area is located around the laser-damaged region, indicating that the guiding effect is stress induced. Refractive-index changes are measured by digital holography. Proper active doping should enable femtosecond processing and waveguide writing in various crystalline materials.
Synthesis of 4Å single-walled carbon nanotubes in catalytic Si-substituted AlPO4-5 molecular sieves
Authors: Li Z. M. , Zhai J. P. , Liu H. J. , Li I. L. , Chan C. T. , Sheng Ping , Tang Z. K.
Published: August 2004

4 Å single-walled carbon nanotubes (SWCNs) were fabricated using Si-substituted AlPO4-5 (SAPO-5) molecular sieves as the template. In comparison with neutral AlPO4-5, the SAPO-5 framework plays an important role as a catalyst in pyrolyzing the hydrocarbon molecules, owing to the Bønsted acid sites. The first-principles calculation shows the Si decoration to be very favorable to the formation of carbon nanotubes in the SAPO-5 channels. The resulting SWCNs have better quality than those fabricated without Si doping, evidenced by clearer and stronger radial breathing modes in the Raman spectra.
Waveguide of amorphous perfluoropolymer for visible light
Authors: Sasaki Kentaro , Kawamura Norikazu , Tokumaru Haruki , Sakane Yoshihiko
Published: August 2004

We developed an amorphous polymer of cyclized perfluoropolymer, which is highly transparent throughout the visible range, and fabricated waveguides of the polymer for visible light. At a wavelength of 405nm, approximately 60% of lightwaves are propagated through the straight waveguide and over 50% of the lightwaves are propagated through the buried waveguides with a radius of more than 30mm, demonstrating the feasibility of the waveguides as light sources with a small angle of a beam divergence in a single mode. The waveguides are prospective candidates for multiple beams in line for parallel information processing, such as optical recording systems.
White light emission from transparent SiO2 glass prepared from nanometer-sized silica particles
Authors: Uchino Takashi , Yamada Tomoko
Published: August 2004

We report that nanometer-sized silicon-dioxide particles are sintered to optical transparency at temperatures even below 1000°C, forming nonporous bulk silica glass. The resultant silica glass exhibits visible emission, which appears white to the naked eye, in the wavelength range from ∼400to∼700nm at room temperature under ultraviolet excitation. The observed emission is quite stable after prolonged exposure to the atmosphere and shows no appreciable light-induced degradation. The present photoluminescence characteristics are found to be basically different from those reported previously for silica nanoparticles and silica-based porous materials.
Metal piezoelectric semiconductor field effect transistors for piezoelectric strain sensors
Authors: Wu Yuh-Renn , Singh Jasprit
Published: August 2004

In this letter, we examine the potential of a functional device that can have good transistor and stress sensor properties. The device examined is based on the use of a thin oxide with high piezoelectric coefficients under the gate region. Channel charge and current are controlled by gate voltage or by stress. We examine the performance of two classes of heterostructures that are important semiconductor technologies: (i) Si∕SiO2∕BaTiO3 heterostructure junctions that would be an important breakthrough for silicon sensor technology and (ii) GaN∕AlN∕BaTiO3 heterostructure field effect transistors. The calculations show that with a very thin piezoelectric layer we can have a highly sensitive stress sensor and transistor. For optimum performance, the piezoelectric layer thickness should be ∼30–60Å.
In vitro shoot regeneration from commercial cultivars of Australian canola (Brassica napus L.)
Authors: Zhang Yan , L. Bhalla Prem
Published: August 2004

Canola, (Brassica napus L.) is an important crop in Australia. Large genetic variability in the Australian canola cultivars is reflected by their diverse agronomic characteristics. Further improvement using modern breeding methods will lead to the generation of better canola varieties suited for Australian conditions. Genetic engineering relies on the development of efficient methods for regeneration of viable shoots from cultured tissues, and the successful application of transformation techniques. This study reports the in vitro shoot regeneration potential from seedling explants of 7 commercial genotypes (Dunkeld, Grouse, RK7, RI25, Oscar, Rainbow, and Monty) of Australian canola. Seedling explants of these genotypes were all responsive to shoot regeneration. Total number of shoots regenerated varied significantly among the 7 genotypes. Based on the number of shoots regenerated, Rainbow was found to be the most amenable to in vitro regeneration with 55% of cotyledon explants regenerating 2.47 shoots per explants on shoot initiation medium containing 6-benzylaminopurine (3 mg/L), 1-naphthylacetic acid (0.2 mg/L), and gibberellic acid (0.01 mg/L). Normal fertile canola plants from all the 7 genotypes were regenerated. The results obtained from this study will form the basis for genetic transformation studies.
Effect of genotype and environment on seed quality in sweet narrow-leafed lupin (Lupinus angustifolius L.)
Authors: Cowling Wallace A. , Tarr Allen
Published: August 2004

Seed quality of 6 sweet narrow-leafed lupin (Lupinus angustifolius) cultivars was measured in 126 field trials in Western Australia over 11 years at 55 locations to determine the effect of locations (l), years (y), genotypes (g), and genotype × environment interactions on total seed alkaloids, seed oil, seed protein, seed size, and hectolitre weight. The variance component for g exceeded the sum of those for g × l, g × y, and g × l × y for all traits. The ranking of cultivars for each seed quality trait was fairly constant across years and locations. The largest variance component was l × y, which indicated that the ranking of locations for seed quality traits was unpredictable from year to year. There was a strong negative correlation between seed oil and seed protein across the 6 cultivars (r = –0.96, P < 0.01) and 126 experiments (r = –0.522, P < 0.001). Large seeds, produced at some experimental sites, were associated with high seed alkaloids and high seed oil. Seed quality traits were not associated with soil pH, latitude, or longitude of the experiments, but low pre-season rainfall was associated with higher hectolitre weight. This study indicates that it should be possible to identify genotypes with superior quality from relatively few field trials. Progress in breeding for protein and oil combined will be slowed by the strong negative genotypic correlation between the two traits.
Could Tetragonisca angustula Latreille (Apinae, Meliponini) be effective as strawberry pollinator in greenhouses?
Authors: Malagodi-Braga Kátia Sampaio , Kleinert Astrid de Matos Peixoto
Published: August 2004

We evaluated the contribution of the stingless bee Tetragonisca angustula as a strawberry pollinator using primary flowers of the ‘Oso Grande’ cultivar. We applied 4 pollination treatments: open-pollination in the field, T. angustula pollination inside a greenhouse, and spontaneous self-pollination in the field and greenhouse. In each treatment we determined berry weight, number of achenes, number of fertilised ovules, fertilisation rates, and the percentage of marketable fruit. The results showed that one colony of this species in a greenhouse with approximately 1350 strawberry plants was adequate to pollinate ‘Oso Grande’ primary flowers. The contribution of T. angustula to the weight and shape of primary berries demonstrated that this bee species is an effective strawberry pollinator and it can promote a significant increase in overall strawberry production.
Effects of combined Actinobacillus pleuropneumoniae challenge and change in environmental temperature on calcitonin receptor expression levels in growing pigs
Authors: Kerr C. A. , Mathews K. O. , Giles L. R. , Jones M. R.
Published: August 2004

We have identified through differential gene expression polymerase chain reaction that porcine calcitonin receptor expression levels could be altered in porcine leukocytes in response to Actinobacillus pleuropneumoniae (App) challenge. This study further investigates the effects of mild pleuropneumonia and changes in environmental temperature, singularly and in combination, on leukocyte expression levels of the calcitonin receptor in domestic pigs. Forty entire male pigs were allocated by weight and temperament at a starting liveweight of 33 0± 5 kg to 4 treatments: control (22°C room temperature); A. pleuropneumoniae challenge (Day 1); varied temperature (15°C for 8 h on Days 0, 1, and 2; 30°C for 24 h on Day 6); and the combined A. pleuropneumoniae challenge and varied temperature treatment. The analysis of the leukocyte expression levels of calcitonin receptor using semi-quantitative reverse transcription PCR revealed that calcitonin receptor was up-regulated in response to the A. pleuropneumoniae challenge (P < 0.001) and the temperature treatment (P < 0.001). In addition, up-regulation of the calcitonin receptor correlated with decreased weight gain, feed intake, and plasma IGF-I. Thus, expression levels of the calcitonin receptor reflect changes in growth performance associated with alteration in ambient temperature and App challenge. In addition, this study indicates that calcitonin receptor expression represents a mechanism through which endocrine and immune systems interact to affect growth.
Feeding strategies for grain-fed cattle in a hot environment
Authors: Holt Simone M. , Gaughan John. B. , Mader Terry L.
Published: August 2004

Six Bos taurus (Hereford) steers (body weight 324 ± 22 kg) were used in a 45-day study with a replicated 3 × 3 Latin-square design. Three treatments [ad libitum feeding (ADLIB); limit feeding, 85% of ad libitum (LIMIT); bunk management feeding where steers were only given access to feed from 1600 to 0800 hours the following day (BUNK)] were imposed over 3 periods, with 2 steers assigned to each treatment in each period. Cattle were managed in a temperature-controlled metabolism unit and were exposed to both thermoneutral (17.7°C–26.1°C) and hot (16.7°C–32.9°C) environmental conditions. By design, during the thermoneutral period, the ADLIB cattle displayed greater intake (P < 0.05) than the LIMIT group, with the BUNK group being intermediate. However, during the hot period, both the LIMIT and BUNK treatment groups increased feed intake 4–5%, whereas feed intake of the ADLIB treatment group declined nearly 2%. During both periods respiration rate (RR, breath/min) followed the same pattern that was observed for feed intake, with the greatest (P < 0.05) RR found in the ADLIB treatment group (81.09 and 109.55, thermoneutral and hot, respectively) and lowest (P < 0.05) RR in the LIMIT treatment group (74.47 and 102.76, thermoneutral and hot, respectively). Rectal temperature (RT) did not differ among treatments during the thermoneutral period or the first hot day, although during the thermoneutral period the ADLIB treatment group did tend to display a lower RT, possibly as a result of other physiological processes (pulse rate and RR) aiding to keep RT lower. During the hot period, differences in RT were found on Day 5, with the LIMIT cattle having lower (P < 0.10) RT (38.92°C) than the ADLIB (39.18°C) cattle, with BUNK cattle RT (39.14°C) being intermediate. However, when hourly data were examined, the ADLIB cattle had greater (P < 0.05) RT than the BUNK and LIMIT at 1800 hours and greater RT (P < 0.05) than the LIMIT group at 1400, 1500, and 1600 hours. Clearly, a change in diurnal RT pattern was obtained by using the LIMIT and BUNK feeding regimen. Both of these groups displayed a peak RT during the hot conditions, between 2100 and 2200 hours, whereas the ADLIB group displayed a peak RT between 1400 and 1500 hours, a time very close to when peak climatic stress occurs.
Based on these results it is apparent that feedlot managers could alleviate the effects of adverse hot weather on cattle by utilising either a limit-feeding regimen or altering bunk management practices to prevent feed from being consumed several hours prior to the hottest portion of the day.
Effects of dietary conjugated linoleic acid on haematological and humoral responses in the grower pig
Authors: Ostrowska E. , Knowles A. , Muralitharan M. , Cross R. F. , Bauman D. E. , Dunshea F. R.
Published: August 2004

The effects of conjugated linoleic acid (CLA) on the levels of total serum leucocytes, granulocytes including neutrophils, basophils, and eosinophils, as well as on monocytes and leucocytes were measured in pigs selected from a clean (minimal disease) herd. Thirty pigs were fed different rates of dietary CLA (0, 1.25, 2.5, 5.0, 7.5, and 10.0 g CLA-55/kg diet) for 8 weeks. Blood samples were collected at the end of the study for assessment of haematological and humoral responses to CLA supplementation. No difference in total white blood cells including the neutrophil, monocyte, and lymphocyte counts was observed among different dietary groups. A dose-dependent reduction (P = 0.02) in eosinophil concentrations suggests that CLA exerts anti-inflammatory activities. A 2-fold increase in the level of basophils was recorded in pigs fed lower levels of CLA (1.25 and 2.5 g CLA/kg diet) but the levels decreased gradually (P = 0.05) and were below the detection limit at the highest rate (10 g/kg) of CLA supplementation. The level of IgG was reduced by over 50% in CLA-fed pigs (P < 0.001), although the response was quadratic in nature (P < 0.001). T-cell population analysis showed that CD4+ cells tended (P = 0.06) to be reduced linearly with increasing inclusion of CLA in the diet. Our results suggest that dietary CLA modulates haematological and humoral responses in a dose-dependent manner.
Stimulating dormancy release and emergence of annual ryegrass (Lolium rigidum) seeds using short-term hydrated storage in darkness
Authors: Steadman Kathryn J. , Bignell Gavin P. , Michael Pippa J.
Published: August 2004

Experiments were performed to determine whether the dormancy release effect of hydrated storage in darkness (dark-stratification) is common amongst annual ryegrass populations and has the potential to occur under field conditions. Dormant seeds from all populations tested (22) became sensitive to light during dark-stratification, enabling them to germinate when subsequently exposed to light. Under controlled temperature (25/15°C), light (12-h photoperiod), and hydration (solidified agar-water) conditions, more seeds germinated by 28 days if the first 14 days were in darkness followed by exposure to light for 12 h per day than if they were exposed to light throughout or darkness throughout. Constraint over the conditions imposed during dark-stratification and germination was gradually reduced to investigate whether the dormancy release effect was diminished. Dark-stratification was effective in promoting germination when performed under natural diurnal temperatures, and burial in moist soil provided suitable conditions for dark-stratification to occur. The surface of moist soil, with natural diurnal temperatures and sunlight, was suitable for germination of dark-stratified seeds. Dark-stratification is a quick and effective means to enhance the sensitivity of dormant annual ryegrass seeds to light, enabling the majority of the population to germinate. However, large quantities of light are required to promote germination of dark-stratified seeds, so buried seeds must be moved to the soil surface to allow exposure to adequate light for germination.
Occurrence of virus infection in seed stocks and 3-year-old pastures of lucerne (Medicago sativa)
Authors: Jones R. A. C.
Published: August 2004

In tests on seed samples from 26 commercial seed stocks of lucerne (Medicago sativa) to be sown in south-western Australia in 2001, infection with Alfalfa mosaic virus (AMV) was found in 21 and Cucumber mosaic virus (CMV) in 3 of them. Bean yellow mosaic virus (BYMV) and Pea seed-borne mosaic virus (PSbMV) were not detected in any. Incidences of infection within individual affected seed samples were 0.1–4% (AMV) and 0.1–0.3% (CMV), and the infected seed stocks were from 3 (CMV) and at least 11 (AMV) different lucerne cultivars. In a survey of 31 three-year-old lucerne pastures in the same region in 2001, in randomly collected samples, AMV was found in 30 and luteovirus infection in 11 pastures. Pastures in high, medium, and low rainfall zones were all infected. Incidences of AMV within individual infected pastures were high, with 50–98% of plants infected in 20 of them and only 3 having <10% infection, but luteovirus incidences were only 1–5%. In addition to various cultivar mixtures, at least 8 (AMV) and 3 (luteoviruses) different individual lucerne cultivars were infected. When the species of luteovirus present were identified, they were Bean leaf roll virus, Beet western yellows virus ( = Turnip yellows virus), or Subterranean clover red leaf virus ( = Soybean dwarf virus). CMV and legume-infecting potyviruses (BYMV, PSbMV, and Clover yellow vein virus) were not detected in any of the lucerne samples. Acyrthosiphon kondoi infestation was common in the samples collected, and A. pisum and Aphis craccivora were also found. Widespread infection in lucerne stands, and their frequent colonisation by aphid vectors, are cause for concern not only because of virus-induced production losses in lucerne itself but also because they provide virus infection reservoirs for spread to nearby grain legume crops and annual legume pastures.