433 research outputs found
Room temperature and low-field resonant enhancement of spin Seebeck effect in partially compensated magnets
Resonant enhancement of spin Seebeck effect (SSE) due to phonons was recently
discovered in Y3Fe5O12 (YIG). This effect is explained by hybridization between
the magnon and phonon dispersions. However, this effect was observed at low
temperatures and high magnetic fields, limiting the scope for applications.
Here we report observation of phonon-resonant enhancement of SSE at room
temperature and low magnetic field. We observed in Lu2BiFe4GaO12 and
enhancement 700 % greater than that in a YIG film and at very low magnetic
fields around 10-1 T, almost one order of magnitude lower than that of YIG. The
result can be explained by the change in the magnon dispersion induced by
magnetic compensation due to the presence of non-magnetic ion substitutions.
Our study provides a way to tune the magnon response in a crystal by chemical
doping with potential applications for spintronic devices.Comment: 17 pages, 4 figure
Tunable space-time crystal in room-temperature magnetodielectrics
We report the experimental realization of a space-time crystal with tunable
periodicity in time and space in the magnon Bose-Einstein Condensate (BEC),
formed in a room-temperature Yttrium Iron Garnet (YIG) film by radio-frequency
space-homogeneous magnetic field. The magnon BEC is prepared to have a well
defined frequency and non-zero wavevector. We demonstrate how the crystalline
"density" as well as the time and space textures of the resulting crystal may
be tuned by varying the experimental parameters: external static magnetic
field, temperature, thickness of the YIG film and power of the radio-frequency
field. The proposed space-time crystals provide a new dimension for exploring
dynamical phases of matter and can serve as a model nonlinear Floquet system,
that brings in touch the rich fields of classical nonlinear waves, magnonics
and periodically driven systems
Confinement of Bose-Einstein magnon condensates in adjustable complex magnetization landscapes
Coherent wave states such as Bose-Einstein condensates (BECs), which
spontaneously form in an overpopulated magnon gas even at room temperature,
have considerable potential for wave-based computing and information processing
at microwave frequencies. The ability to control the transport properties of
magnon BECs plays an essential role for their practical use. Here, we
demonstrate spatio-temporal control of the BEC density distribution through the
excitation of magnon supercurrents in an inhomogeneously magnetized yttrium
iron garnet film. The BEC is created by microwave parametric pumping and probed
by Brillouin light scattering spectroscopy. The desired magnetization profile
is prepared by heating the film with optical patterns projected onto its
surface using a phase-based wavefront modulation technique. Specifically, we
observe a pronounced spatially localized magnon accumulation caused by magnon
supercurrents flowing toward each other originating in two heated regions. This
accumulation effect increases the BEC lifetime due to the constant influx of
condensed magnons into the confinement region. The shown approach to manipulate
coherent waves provides an opportunity to extend the lifetime of freely
evolving magnon BECs, create dynamic magnon textures, and study the interaction
of magnon condensates formed in different regions of the sample.Comment: 8 pages, 4 figure
Out-of-Plane Magnetic Anisotropy in Ordered Ensembles of FeN Nanocrystals Embedded in GaN
Phase-separated semiconductors containing magnetic nanostructures are
relevant systems for the realization of high-density recording media. Here, the
controlled strain engineering of GaFeN layers with FeN embedded
nanocrystals (NCs) \textit{via} AlGaN buffers with different Al
concentration \% is presented. Through the addition of Al
to the buffer, the formation of predominantly prolate-shaped
-FeN NCs takes place. Already at an Al concentration
\,\,5\% the structural properties---phase, shape,
orientation---as well as the spatial distribution of the embedded NCs are
modified in comparison to those grown on a GaN buffer. Although the magnetic
easy axis of the cubic '-GaFeN nanocrystals in the layer on
the buffer lies in-plane, the easy axis of the
-FeN NCs in all samples with AlGaN buffers
coincides with the growth direction, leading to a sizeable
out-of-plane magnetic anisotropy and opening wide perspectives for
perpendicular recording based on nitride-based magnetic nanocrystals.Comment: 29 pages, 10 figures, submitte
The impact of quantitative optimization of hybridization conditions on gene expression analysis.
BACKGROUND: With the growing availability of entire genome sequences, an increasing number of scientists can exploit oligonucleotide microarrays for genome-scale expression studies. While probe-design is a major research area, relatively little work has been reported on the optimization of microarray protocols. RESULTS: As shown in this study, suboptimal conditions can have considerable impact on biologically relevant observations. For example, deviation from the optimal temperature by one degree Celsius lead to a loss of up to 44% of differentially expressed genes identified. While genes from thousands of Gene Ontology categories were affected, transcription factors and other low-copy-number regulators were disproportionately lost. Calibrated protocols are thus required in order to take full advantage of the large dynamic range of microarrays.For an objective optimization of protocols we introduce an approach that maximizes the amount of information obtained per experiment. A comparison of two typical samples is sufficient for this calibration. We can ensure, however, that optimization results are independent of the samples and the specific measures used for calibration. Both simulations and spike-in experiments confirmed an unbiased determination of generally optimal experimental conditions. CONCLUSIONS: Well calibrated hybridization conditions are thus easily achieved and necessary for the efficient detection of differential expression. They are essential for the sensitive pro filing of low-copy-number molecules. This is particularly critical for studies of transcription factor expression, or the inference and study of regulatory networks.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are
Electroexcitation of the Roper resonance from CLAS data
The helicity amplitudes of the electroexcitation of the Roper resonance on
proton are extracted at 1.7 < Q2 < 4.2 GeV2 from recent high precision
JLab-CLAS cross sections data and longitudinally polarized beam asymmetry for
pi+ electroproduction on protons. The analysis is made using two approaches,
dispersion relations and unitary isobar model, which give consistent results.
It is found that the transverse helicity amplitude for the gamma* p -->
P11(1440) transition, which is large and negative at Q2=0, becomes large and
positive at Q2 ~ 2 GeV2, and then drops slowly with Q2. Longitudinal helicity
amplitude, that was previously found from CLAS data as large and positive at
Q2=0.4,0.65 GeV2, drops with Q2. These results rule out the presentation of
P11(1440) as a 3qG hybrid state, and provide strong evidence in favor of this
resonance as a first radial excitation of the 3q ground state.Comment: 3 pages, 2 figures, Talk on the Workshop on "The Physics of Excited
Nucleons", Bonn, Germany, October 200
Long-distance supercurrent transport in a room-temperature Bose-Einstein magnon condensate
The term supercurrent relates to a macroscopic dissipation-free collective
motion of a quantum condensate and is commonly associated with such famous
low-temperature phenomena as superconductivity and superfluidity. Another type
of motion of quantum condensates is second sound - a wave of the density of a
condensate. Recently, we reported on an enhanced decay of a parametrically
induced Bose-Einstein condensate (BEC) of magnons caused by a supercurrent
outflow of the BEC phase from the locally heated area of a room temperature
magnetic film. Here, we present the direct experimental observation of a
long-distance spin transport in such a system. The condensed magnons being
pushed out from the potential well within the heated area form a density wave,
which propagates through the BEC many hundreds of micrometers in the form of a
specific second sound pulse - Bogoliubov waves - and is reflected from the
sample edge. The discovery of the long distance supercurrent transport in the
magnon BEC further advances the frontier of the physics of quasiparticles and
allows for the application of related transport phenomena for low-loss data
transfer in perspective magnon spintronics devices
Farmacocinética de la cefalexina administrada por vía oral conjuntamente con enalapril en caninos adultos
El objetivo de este estudio fue caracterizar la farmacocinética de la cefalexina administrada por vía oral a caninos y determinar si la administración conjunta con enalapril produce modificaciones en la misma. Se trabajó con 6 caninos mestizos sanos. Cada uno recibió una dosis única de 25 mg/kg de una suspensión de cefalexina (grupo 1) o cefalexina 20 minutos después de administrada una dosis oral única de 0,5 mg/kg de enalapril (grupo 2), con un diseño cross over (3x3). Las concentraciones plasmáticas de cefalexina se determinaron mediante el método microbiológico. El T>CIM fue siempre superior al 60% del intervalo posológico de 12 horas para ambos grupos. Los parámetros farmacocinéticos se compararon mediante el test de Wilcoxon (p≤0,05). Los resultados obtenidos se expresaron como media ± desvío estándar y para los grupos 1 y 2 fueron respectivamente: Cmax 27,66±4,20 y 26,51±6,04 μg/ml, Tmax 1,41±0,58 y 1,58±0,58 h, T1/2 1,55±0,12 y 1,62±0,22 h, ABC0-∞ 110,8±10,98 y 110,6±17,64 μg·h/ml, TMR 3,19±0,39 y 3,46±0,55 h. No se encontraron diferencias estadísticamente significativas entre los parámetros farmacocinéticos de efalexina obtenidos en cada grupo, por lo cual nuestros resultados sugieren que el tratamiento simultáneo con ambas drogas no modifica la farmacocinética del antibiótico
Experimental observation of Josephson oscillations in a room-temperature Bose-Einstein magnon condensate
The alternating current (ac) Josephson effect in a time-independent
spatially-inhomogeneous setting is manifested by the occurrence of Josephson
oscillations - periodic macroscopic phase-induced collective motions of the
quantum condensate. So far, this phenomenon was observed at cryogenic
temperatures in superconductors, in superfluid helium, and in Bose-Einstein
condensates (BECs) of trapped atoms. Here, we report on the discovery of the ac
Josephson effect in a magnon BEC carried by a room-temperature ferrimagnetic
film. The BEC is formed in a parametrically populated magnon gas in the spatial
vicinity of a magnetic trench created by a dc electric current. The appearance
of the Josephson effect is manifested by oscillations of the magnon BEC density
in the trench, caused by a coherent phase shift between this BEC and the BEC in
the nearby regions. Our findings advance the physics of room-temperature
macroscopic quantum phenomena and will allow for their application for data
processing in magnon spintronics devices
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