15,378 research outputs found

    Nanoscale Quantification of Octahedral Tilts in Perovskite Films

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    NiO6-octahedral tilts in ultrathin LaNiO3 films were studied using position averaged convergent beam electron diffraction (PACBED) in scanning transmission electron microscopy. Both the type and magnitude of the octahedral tilts were determined by comparing PACBED experiments to frozen phonon multislice simulations. It is shown that the out-of-plane octahedral tilt of an epitaxial film under biaxial tensile stress (0.78 % in-plane tensile strain) increases by ~ 20%, while the in-plane rotation decreases by ~ 80%, compared to the unstrained bulk material.Comment: The manuscript has been accepted by Applied Physics Letters. After it is published, it will be found at: http://apl.aip.org

    Mean Field Theoretical Structure of He and Be Isotopes

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    The structures of He and Be even-even isotopes are investigated using an axially symmetric Hartree-Fock approach with a Skyrme-IIIls mean field potential. In these simple HF calculations, He and Be isotopes appear to be prolate in their ground states and Be isotopes have oblate shape isomeric states. It is also shown that there exists a level crossing when the nuclear shape changes from the prolate state to the oblate state. The single neutron levels of Be isotopes exhibit a neutron magic number 6 instead of 8 and show that the level inversion between 1/2- and 1/2+ levels occurs only for a largely deformed isotope. Protons are bound stronger in the isotope with more neutrons while neutron levels are somewhat insensitive to the number of neutrons and thus the nuclear size and also the neutron skin become larger as the neutron number increases. In these simple calculations with Skyrme-IIIls interaction no system with a clear indication of neutron halo was found among He and Be isotopes. Instead of it we have found 8He+2n, 2n+8He+2n, and 16Be+2n like chain structures with clusters of two correlated neutrons. It is also shown that 8He and 14Be in their ground states are below the neutron drip line in which all nucleons are bound with negative energy and that 16Be in its ground state is beyond the neutron drip line with two neutrons in positive energy levels.Comment: CM energy correction, 1 figure and more discussions adde

    Kinetically-controlled thin-film growth of layered β\beta- and γ\gamma-Nax_{x}CoO2_{2} cobaltate

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    We report growth characteristics of epitaxial β\beta-Na0.6_{0.6}CoO2_{2} and γ\gamma-Na0.7_{0.7}CoO2_{2} thin films on (001) sapphire substrates grown by pulsed-laser deposition. Reduction of deposition rate could change structure of Nax_{x}CoO2_{2} thin film from β\beta-phase with island growth mode to γ\gamma-phase with layer-by-layer growth mode. The γ\gamma-Na0.7_{0.7}CoO2_{2} thin film exhibits spiral surface growth with multiterraced islands and highly crystallized texture compared to that of the β\beta-Na0.6_{0.6}CoO2_{2} thin film. This heterogeneous epitaxial film growth can give opportunity of strain effect of physical properties and growth dynamics of Nax_{x}CoO2_{2} as well as subtle nature of structural change.Comment: accepted for publication in Applied Physics Letter

    Infrared Hall conductivity of Na0.7_{0.7}CoO2_2

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    We report infrared Hall conductivity σxy(ω)\sigma_{xy}(\omega) of Na0.7_{0.7}CoO2_2 thin films determined from Faraday rotation angle θF\theta_{F} measurements. σxy(ω)\sigma_{xy}(\omega) exhibits two types of hole conduction, Drude and incoherent carriers. The coherent Drude carrier shows a large renormalized mass and Fermi liquid-like behavior of Hall scattering rate, γHaT2\gamma_{H} \sim aT^{2}. The spectral weight is suppressed and disappears at T = 120K. The incoherent carrier response is centered at mid-IR frequency and shifts to lower energy with increasing T. Infrared Hall constant is positive and almost independent of temperature in sharp contrast with the dc-Hall constant.Comment: 5 Pages, 5 Figures. Author list corrected in metadata only, paper is unchange

    Unusual superexchange pathways in a Ni triangular lattice of NiGa2_2S4_4 with negative charge-transfer energy

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    We have studied the electronic structure of the Ni triangular lattice in NiGa2_2S4_4 using photoemission spectroscopy and subsequent model calculations. The cluster-model analysis of the Ni 2pp core-level spectrum shows that the S 3pp to Ni 3dd charge-transfer energy is \sim -1 eV and the ground state is dominated by the d9Ld^9L configuration (LL is a S 3pp hole). Cell perturbation analysis for the NiS2_2 triangular lattice indicates that the strong S 3pp hole character of the ground state provides the enhanced superexchange interaction between the third nearest neighbor sites.Comment: 10 pages, 5 figures, accepted to PR

    Species Differentiation Of Fish Samples By Restriction Fragment Length Polymorphism Analysis Of Cytochrome B Gene

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    Metode pengukuran polimorfisme fragmen hasil pemotongan produkreaksi polimorfik berantai oleh enzim restriksi spesifik (polymerase chainreaction-restriction fragment length polymorphism, RFLP-PCR) telah digunakanuntuk membedakan beberapa jenis ikan mentah. Situs cytochrome b mitokondria,yang diamplifikasi oleh primer universal, dipotong menggunakan empat enzimrestriksi (Bfa I, Hinf I, Msp I, Mbo II) sehingga dapat dianalisa fragment-fragmentpendeknya. Hasil yang diperolah dari pemotongan oleh enzim restriksi tersebutternyata dapat digunakan untuk membedakan tiap jenis ikan sampel. Hasilpenelitian ini menunjukkan bahwa PCR dan RFLP-PCR merupakan metode yangsensitif dan dapat dilakukan dalam waktu singkat untuk membedakan berbagaijenis ikan mentah

    Structural origins of the properties of rare earth nickelate superlattices

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    NiO6 octahedral tilts in the LaNiO3/SrTiO3 superlattices are quantified using position averaged convergent beam electron diffraction in scanning transmission electron microscopy. It is shown that maintaining oxygen octahedra connectivity across the interface controls the octahedral tilts in the LaNiO3 layers, their lattice parameters and their transport properties. Unlike films and layers that are connected on one side to the substrate, subsequent LaNiO3 layers in the superlattice exhibit a relaxation of octahedral tilts towards bulk values. This relaxation is facilitated by correlated tilts in SrTiO3 layers and is correlated with the conductivity enhancement of the LaNiO3 layers in the superlattices relative to individual films.Comment: Accepted for publication in Physical Review B (Rapid Communication

    3-D self-assembly of flower-like particles via microwave irradiation for water treatment

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    Three-dimensional (3-D) flower-like shape (FLS) Fe 3O 4 and Fe particles were successfully synthesized using FLS precursor particles that are prepared through a facile microwave-assisted reaction. The mechanism underlying the self-assembly process and shape evolution of FLS particles was systematically investigated by changing reaction parameters such as reaction temperature, reaction time and reaction pressure. During the reaction, iron alkoxide, α-Fe 2O 3 and FeOOH nanoparticles are formed first and are subsequently transformed to 3-D hierarchical FLS particles by the self-assembly of the primary nanoparticles. Reaction temperature and pressure play critical roles in the formation of the hierarchical flower-like superstructure. There is an optimum window of the reaction temperature (∼180 °C) for the formation of 3-D FLS particles, which is attributed to the competition between the self-assembly process and growth process of the nanoparticles. Also, since FeCl 3, ethylene glycol, and urea are used together as raw materials, the appearance of FLS particles is strongly dependent on the reaction pressure. As the reaction pressure becomes larger than 1 MPa, the flake type particles become more thermodynamically favorable than the FLS particles, due to the limited decomposition of urea. Brunauer-Emmett-Teller (BET) analysis shows that FLS particles have a large surface area (>40 m 2 g -1). Because of their high specific surface area and intrinsic reactivity, FLS particles efficiently remove sulfur ions in aqueous solution. This suggests that these flower-like particles can be promising materials to treat toxic gas such as H 2S in an environment-friendly way. © 2012 The Royal Society of Chemistry
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