1,016 research outputs found
On stoichiometry and intermixing at the spinel/perovskite interface in CoFe2O4/BaTiO3 thin films
The performance of complex oxide heterostructures depends primarily on the interfacial coupling of the two component structures. This interface character inherently varies with the synthesis method and conditions used since even small composition variations can alter the electronic, ferroelectric, or magnetic functional properties of the system. The focus of this article is placed on the interface character of a pulsed laser deposited CoFe2O4/BaTiO3 thin film. Using a range of state-of-the-art transmission electron microscopy methodologies, the roles of substrate morphology, interface stoichiometry, and cation intermixing are determined on the atomic level. The results reveal a surprisingly uneven BaTiO3 substrate surface formed after the film deposition and Fe atom incorporation in the top few monolayers inside the unit cell of the BaTiO3 crystal. Towards the CoFe2O4 side, a disordered region extending several nanometers from the interface was revealed and both Ba and Ti from the substrate were found to diffuse into the spinel layer. The analysis also shows that within this somehow incompatible composite interface, a different phase is formed corresponding to the compound Ba2Fe3Ti5O15, which belongs to the ilmenite crystal structure of FeTiO3 type. The results suggest a chemical activity between these two oxides, which could lead to the synthesis of complex engineered interfaces
Data analysis of gravitational-wave signals from spinning neutron stars. V. A narrow-band all-sky search
We present theory and algorithms to perform an all-sky coherent search for
periodic signals of gravitational waves in narrow-band data of a detector. Our
search is based on a statistic, commonly called the -statistic,
derived from the maximum-likelihood principle in Paper I of this series. We
briefly review the response of a ground-based detector to the
gravitational-wave signal from a rotating neuron star and the derivation of the
-statistic. We present several algorithms to calculate efficiently
this statistic. In particular our algorithms are such that one can take
advantage of the speed of fast Fourier transform (FFT) in calculation of the
-statistic. We construct a grid in the parameter space such that
the nodes of the grid coincide with the Fourier frequencies. We present
interpolation methods that approximately convert the two integrals in the
-statistic into Fourier transforms so that the FFT algorithm can
be applied in their evaluation. We have implemented our methods and algorithms
into computer codes and we present results of the Monte Carlo simulations
performed to test these codes.Comment: REVTeX, 20 pages, 8 figure
Age-related changes in anaerobic power in the former highly trained oarsmen and kayakers
The purpose of this study was to evaluate the age-related changes in anaerobic power in the former highly trained oarsmen and kayakers, i.e. the representatives of sports requiring high endurance capacity and strength. Sixty-six former athletes, aged 30-67 years participated in this study. The subjects were assessed for peak anaerobic power in arms (Pan arms) and legs (Pan legs) during 10 s- maximal cycle ergometer exercise tests and for peak aerobic power (PVO2max) during incremental exercise. Body mass, lean body mass and body fat content were measured as well. The peak anaerobic power decline in the former highly trained athletes examined in the present study equalled to 0.6-0.7% per year. The recreational physical activity, based primarily on the endurance exercises, did not affect the peak anaerobic power whereas the peak aerobic power and body fat content strongly depended on the age and physical activity. The peak anaerobic power in the upper and lower extremities exhibited similar reduction with age of the subjects. Furthermore, in the less active group the ratio of Pan legs to PVO2max did not change with age whereas in physically active subjects this index increased. It was concluded that in the sample of former highly trained oarsmen and kayakers the age-related decline in the peak anaerobic power approximated that reported by other authors for untrained or endurance trained subjects, the peak anaerobic power in the arms was almost the same as that in the legs and that in the less active group the ratio of the peak anaerobic power to the peak aerobic power was independent of age and strongly tended to increase in the physically active subjects
Constraints on the luminosity of the stellar remnant in SNR1987A
We obtain photometric constraints on the luminosity of the stellar remnant in
SNR1987A using XMM-Newton and INTEGRAL data. The upper limit in the 2--10 keV
band based on the XMM-Newton data is L<5*10^{34}erg/s. We note, however, that
the optical depth of the envelope is still high in the XMM-Newton band,
therefore, this upper limit does not constrain the true unabsorbed luminosity
of the central source. The optical depth is expected to be small in the hard
X-ray band of the IBIS telescope aboard the INTEGRAL observatory, therefore it
provides an unobscured look at the stellar remnant. We did not detect
statistically significant emission from SN1987A in the 20-60 keV band with the
upper limit of L<1.1*10^{36}erg/s. We also obtained an upper limit on the mass
of radioactive 44Ti M(44Ti)<10^{-3}Msun.Comment: 5 pages, 3 figures, accepted for publication in Astronomy Letter
X-Ray Synchrotron Emitting Fe-Rich Ejecta in SNR RCW 86
Supernova remnants may exhibit both thermal and nonthermal X-ray emission. We
present Chandra observations of RCW 86. Striking differences in the morphology
of X-rays below 1 keV and above 2 keV point to a different physical origin.
Hard X-ray emission is correlated fairly well with the edges of regions of
radio emission, suggesting that these are the locations of shock waves at which
both short-lived X-ray emitting electrons, and longer-lived radio-emitting
electrons, are accelerated. Soft X-rays are spatially well-correlated with
optical emission from nonradiative shocks, which are almost certainly portions
of the outer blast wave. These soft X-rays are well fit with simple thermal
plane-shock models. Harder X-rays show Fe K alpha emission and are well
described with a similar soft thermal component, but a much stronger
synchrotron continuum dominating above 2 keV, and a strong Fe K alpha line.
Quantitative analysis of this line and the surrounding continuum shows that it
cannot be produced by thermal emission from a cosmic-abundance plasma; the
ionization time is too short, as shown both by the low centroid energy (6.4
keV) and the absence of oxygen lines below 1 keV. Instead, a model of a plane
shock into Fe-rich ejecta, with a synchrotron continuum, provides a natural
explanation. This requires that reverse shocks into ejecta be accelerating
electrons to energies of order 50 TeV. We show that maximum energies of this
order can be produced by radiation-limited diffusive shock acceleration at the
reverse shocks.Comment: ApJ, accepted; full resolution images in
http://spider.ipac.caltech.edu/staff/rho/rcw86chandra.p
A Deep Chandra Observation of Kepler's Supernova Remnant: A Type Ia Event with Circumstellar Interaction
We present initial results of a 750 ks Chandra observation of the remnant of
Kepler's supernova of AD 1604. The strength and prominence of iron emission,
together with the absence of O-rich ejecta, demonstrate that Kepler resulted
from a thermonuclear supernova, even though evidence for circumstellar
interaction is also strong. We have analyzed spectra of over 100 small regions,
and find that they fall into three classes. (1) The vast majority show Fe L
emission between 0.7 and 1 keV and Si and S K alpha emission; we associate
these with shocked ejecta. A few of these are found at or beyond the mean blast
wave radius. (2) A very few regions show solar O/Fe abundance rations; these we
associate with shocked circumstellar medium (CSM). Otherwise O is scarce. (3) A
few regions are dominated by continuum, probably synchrotron radiation.
Finally, we find no central point source, with a limit about 100 times fainter
than the central object in Cas A. The evidence that the blast wave is
interacting with CSM may indicate a Ia explosion in a more massive progenitor.Comment: Accepted by ApJ Letter
Quasiparticle spectrum of the hybrid s+g-wave superconductors YNi_2B_2C and LuNi_2B_2C
Recent experiments on single crystals of YNiBC have revealed the
presence of point nodes in the superconducting energy gap Delta(k} at k =
(1,0,0), (0,1,0), (-1,0,0), and (0,-1,0). In this paper we investigate the
effects of impurity scattering on the quasiparticle spectrum in the vortex
state of s+g-wave superconductors, which is found to be strongly modified in
the presence of disorder. In particular, a gap in the quasiparticle energy
spectrum is found to open even for infinitesimal impurity scattering, giving
rise to exponentially activated thermodynamic response functions, such as the
specific heat, the spin susceptibility, the superfluid density, and the nuclear
spin lattice relaxation. Predictions derived from this study can be verified by
measurements of the angular dependent magnetospecific heat and the
magnetothermal conductivity.Comment: 8 pages, RevTex, 4 figure
Key role of the meniscus shape in crystallization of organic semiconductors during meniscus-guided coating
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