59,319 research outputs found
Giant isotope effect and spin state transition induced by oxygen isotope exchange in (
We systematically investigate effect of oxygen isotope in
which shows a crossover with x from
ferromagnetic metal to the insulator with spin-state transition. A striking
feature is that effect of oxygen isotope on the ferromagnetic transition is
negligible in the metallic phase, while replacing with leads
to a giant up-shift of the spin-state transition temperature () in the
insulating phase, especially shifts from 36 to 54 K with isotope
component for the sample with x=0.175. A metal-insulator
transition is induced by oxygen isotope exchange in the sample x=0.172 being
close to the insulating phase. The contrasting behaviors observed in the two
phases can be well explained by occurrence of static Jahn-Teller distortions in
the insulating phase, while absence of them in the metallic phase.Comment: 4 pages, 5 figure
Strain and Electronic Nematicity in La₂₋ₓSrₓCuO₄
Electronic nematicity has previously been observed in La2-xSrxCuO4 thin films by the angle-resolved transverse resistivity method with a director whose orientation is always pinned to the crystal axes when the film is grown on an orthorhombic substrate but not when the substrate is tetragonal. Here we report on measurements of thin films grown on (tetragonal) LaSrAlO4 and subsequently placed in an apparatus that allows the application of uniaxial compressive strain. The apparatus applied enough force to produce a 1% orthorhombicity in LaSrAlO4 and yet no change in the electronic nematicity was observed in films under strain compared to when they were unstrained. The lattice effects are weak, and the origin of nematicity is primarily electronic
Transgenic Italian ryegrass ( Lolium multiflorum ) plants from microprojectile bombardment of embryogenic suspension cells
Transgenic forage-type Italian ryegrass (Lolium multiflorum Lam.) plants have been obtained by microprojectile bombardment of embryogenic suspension cells using a chimeric hygromycin phosphotransferase (hph) gene construct driven by riceActl 5′ regulatory sequences. Parameters for the bombardment of embryogenic suspension cultures with the particle inflow gun were partially optimized using transient expression assays of a chimericβ-glucuronidase (gusA) gene driven by the maizeUbi1 promoter. Stably transformed clones were recovered with a selection scheme using hygromycin in liquid medium followed by a plate selection. Plants were regenerated from 33% of the hygromycin-resistant calli. The transgenic nature of the regenerated plants was demonstrated by Southern hybridization analysis. Expression of the transgene in transformed adult Italian ryegrass plants was confirmed by northern analysis and a hygromycin phosphotransferase enzyme assa
Novel method for refinement of retained austenite in micro/nano-structured bainitic steels
A comparative study was conducted to assess the effects of two different heat treatments on the amount and morphology of the retained austenite in a micro/nano-structured bainitic steel. The heat treatments used in this work were two-stage bainitic transformation and bainitic-partitioning transformation. Both methods resulted in the generation of a multi-phase microstructure containing nanoscale bainitic ferrite, and/or fresh martensitic phases and much finer retained austenite. Both heat treatments were verified to be effective in refining the retained austenite in micro/nano-structured bainite and increasing the hardness. However, the bainitic transformation followed by partitioning cycle was proved to be a more viable approach than the two-stage bainitic transformation due to much shorter processing time, i.e. ∼2 h compared to ∼4 day, respectively
Suppression of the superconducting energy gap in intrinsic Josephson junctions of single crystals
We have observed back-bending structures at high bias current in the
current-voltage curves of intrinsic Josephson junctions. These structures may
be caused by nonequilibrium quasiparticle injection and/or Joule heating. The
energy gap suppression varies considerably with temperature. Different levels
of the suppression are observed when the same level of current passes through
top electrodes of different sizes. Another effect which is seen and discussed,
is a super-current ``reentrance'' of a single intrinsic Josephson junction with
high bias current.Comment: accepted by Supercond. Sci. and Tech., 200
Rare case of magnetic Ag ion: double perovskite CsKAgF
Normally or transition metals are in a low-spin state. Here using
first-principles calculations, we report on a rare case of a high-spin =1
magnetic state for the Ag ion in the double perovskite
CsKAgF. We also explored a possibility of a conventional low-spin
=0 ground state and find an associated tetragonal distortion to be 0.29
{\AA}. However, the lattice elastic energy cost and the Hund exchange loss
exceed the e crystal-field energy gain, thus making the low-spin
tetragonal structure less favorable than the high-spin cubic structure. We
conclude that the compact perovskite structure of CsKAgF is an
important factor in stabilizing the unusual high-spin ground state of
Ag.Comment: 6 pages, 6 figures, accepted for publication in PR
Uncertainties of reverberation time estimation via adaptively identified room impulse responses
© 2016 Acoustical Society of America. This paper investigates the reverberation time estimation methods which employ backward integration of adaptively identified room impulse responses (RIRs). Two kinds of conditions are considered; the first is the "ideal condition" where the anechoic and reverberant signals are both known a priori so that the RIRs can be identified using system identification methods. The second is that only the reverberant speech signal is available, and blind identification of the RIRs via dereverberation is employed for reverberation time estimation. Results show that under the "ideal condition," the average relative errors in 7 octave bands are less than 2% for white noise and 15% for speech, respectively, when both the anechoic and reverberant signals are available. In contrast, under the second condition, the average relative errors of the blindly identified RIR-based reverberation time estimation are around 20%-30% except the 63 Hz octave band. The fluctuation of reverberation times estimated under the second condition is more severe than that under the ideal condition and the relative error for low frequency octave bands is larger than that for high octave bands under both conditions
Nonequilibrium 1/f Noise in Low-doped Manganite Single Crystals
1/f noise in current biased La0.82Ca0.18MnO3 crystals has been investigated.
The temperature dependence of the noise follows the resistivity changes with
temperature suggesting that resistivity fluctuations constitute a fixed
fraction of the total resistivity, independently of the dissipation mechanism
and magnetic state of the system. The noise scales as a square of the current
as expected for equilibrium resistivity fluctuations. However, at 77 K at bias
exceeding some threshold, the noise intensity starts to decrease with
increasing bias. The appearance of nonequilibrium noise is interpreted in terms
of bias dependent multi-step indirect tunneling.Comment: 4pages, 3figures,APL accepte
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