4,687 research outputs found
Giant electrocaloric effect in thin film Pb Zr_0.95 Ti_0.05 O_3
An applied electric field can reversibly change the temperature of an
electrocaloric material under adiabatic conditions, and the effect is strongest
near phase transitions. This phenomenon has been largely ignored because only
small effects (0.003 K V^-1) have been seen in bulk samples such as
Pb0.99Nb0.02(Zr0.75Sn0.20Ti0.05)0.98O3 and there is no consensus on macroscopic
models. Here we demonstrate a giant electrocaloric effect (0.48 K V^-1) in 300
nm sol-gel PbZr0.95Ti0.05O3 films near the ferroelectric Curie temperature of
222oC. We also discuss a solid state device concept for electrical
refrigeration that has the capacity to outperform Peltier or magnetocaloric
coolers. Our results resolve the controversy surrounding macroscopic models of
the electrocaloric effect and may inspire ab initio calculations of
electrocaloric parameters and thus a targeted search for new materials.Comment: 5 pages, 4 figure
Light scattering from a magnetically tunable dense random medium with weak dissipation : ferrofluid
We present a semi-phenomenological treatment of light transmission through
and its reflection from a ferrofluid, which we regard as a magnetically tunable
system of dense random dielectric scatterers with weak dissipation. Partial
spatial ordering is introduced by the application of a transverse magnetic
field that superimposes a periodic modulation on the dielectric randomess. This
introduces Bragg scattering which effectively enhances the scattering due to
disorder alone, and thus reduces the elastic mean free path towards Anderson
localization. Our theoretical treatment, based on invariant imbedding, gives a
simultaneous decrease of transmission and reflection without change of incident
linear polarisation as the spatial order is tuned magnetically to the Bragg
condition, namely the light wave vector being equal to half the Bragg vector
(Q). Our experimental observations are in qualitative agreement with these
results. We have also given expressions for the transit (sojourn) time of light
and for the light energy stored in the random medium under steady illumination.
The ferrofluid thus provides an interesting physical realization of effectively
a "Lossy Anderson-Bragg" (LAB) cavity with which to study the effect of the
interplay of spatial disorder, partial order and weak dissipation on light
transport. Given the current interest in propagation, optical limiting and
storage of light in ferrofluids, the present work seems topical
Nanoscale magnetic structure of ferromagnet/antiferromagnet manganite multilayers
Polarized Neutron Reflectometry and magnetometry measurements have been used
to obtain a comprehensive picture of the magnetic structure of a series of
La{2/3}Sr{1/3}MnO{3}/Pr{2/3}Ca{1/3}MnO{3} (LSMO/PCMO) superlattices, with
varying thickness of the antiferromagnetic (AFM) PCMO layers (0<=t_A<=7.6 nm).
While LSMO presents a few magnetically frustrated monolayers at the interfaces
with PCMO, in the latter a magnetic contribution due to FM inclusions within
the AFM matrix was found to be maximized at t_A~3 nm. This enhancement of the
FM moment occurs at the matching between layer thickness and cluster size,
where the FM clusters would find the optimal strain conditions to be
accommodated within the "non-FM" material. These results have important
implications for tuning phase separation via the explicit control of strain.Comment: 4 pages, submitted to PR
Unsupervised domain adaptation under label space mismatch for speech classification
Unsupervised domain adaptation using adversarial learning has shown promise in adapting speech models from a labeled source domain to an unlabeled target domain. However, prior works make a strong assumption that the label spaces of source and target domains are identical, which can be easily violated in real-world conditions. We present AMLS, an end-to-end architecture that performs Adaptation under Mismatched Label Spaces using two weighting schemes to separate shared and private classes in each domain. An evaluation on three speech adaptation tasks, namely gender, microphone, and emotion adaptation, shows that AMLS provides significant accuracy gains over baselines used in speech and vision adaptation tasks. Our contribution paves the way for applying UDA to speech models in unconstrained settings with no assumptions on the source and target label spaces
A nano-biosensor for DNA sequence detection using absorption spectra of SWNT-DNA composite
biosensor based on Single Walled Carbon Nanotube (SWNT)-Poly (GT)n ssDNA hybrid has been developed for medical diagnostics. The absorption spectrum of this assay is determined with the help of a Shimadzu UV-VIS-NIR spectrophotometer. Two
distinct bands each containing three peaks corresponding to first and second van Hove singularities in the density of states of the nanotubes were observed in the absorption spectrum. When a single-stranded DNA (ssDNA) having a sequence
complementary to probic DNA is added to the ssDNA-SWNT conjugates, hybridization takes place, which causes the red shift of absorption spectrum of nanotubes. On the
other hand, when the DNA is noncomplementary, no shift in the absorption spectrum occurs since hybridization between the DNA and probe does not take place. The red shifting of the spectrum is considered to be due to change in the dielectric
environment around nanotubes.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2212
Charmonium Spectrum from Quenched QCD with Overlap Fermions
We present preliminary results using overlap fermions for the charmonium
spectrum, in particular for hyperfine splitting. Simulations are performed on
lattices, with Wilson gauge action at .
Depending on how the scale is set, we obtain 104(5) MeV (using
) or 88(4) MeV (using =0.5 fm) for the hyperfine
splitting.Comment: 3 pages, 5 fiugres. Talk presented at Lattice 2004 (heavy
The structure of intercalated water in superconducting NaCoO1.37DO: Implications for the superconducting phase diagram
We have used electron and neutron powder diffraction to elucidate the
structural properties of superconducting \NaD. Our measurements show that our
superconducting sample exhbits a number of supercells ranging from
to , but the most predominant one, observed also in the neutron
data, is a double hexagonal cell with dimensions \dhx. Rietveld analysis
reveals that \deut\space is inserted between CoO sheets as to form a
layered network of NaO triangular prisms. Our model removes the need to
invoke a 5K superconducting point compound and suggests that a solid solution
of Na is possible within a constant amount of water .Comment: 4 pages, 3 figure
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