378 research outputs found
Математическое моделирование явления теплообмена в условиях фазового перехода и конвекции
We present a simple and compact design for an all-solid-state laser amplifier system which can output 9.43-kHz 630-ps, 3.5-W pulse trains under 20W absorbed pumping power. The excellent matching between the repetition of its seed source and the fluorescence lifetime of the amplifying medium makes it quiet efficient for the four-pass amplifier to be pumped in cw mode without need of any synchronization device between the oscillator and the amplifier. The entire setup just covers an area of 55x25cm2. The output average power fluctuation is less than +/- 1.5% within 10min and 3% within 6h
Bulk experimental evidence of half-metallic ferromagnetism in doped manganites
We report precise measurements and quantitative data analysis on the
low-temperature resistivity of several ferromagnetic manganite films. We
clearly show that there exists a T^{4.5} term in low-temperature resistivity,
and that this term is in quantitative agreement with the quantum theory of
two-magnon scattering for half metallic ferromagnets. Our present results
provide the first bulk experimental evidence of half-metallic ferromagnetism in
doped manganites.Comment: 4 pages, 4 figure
Probing unparticle theory via lepton flavor violating process at BESIII
The lepton flavor violating process serves as an
ideal place to probe the unparticle theory. Such process can only occur at loop
level in the Standard model (SM), so that should be very suppressed, by
contrast in unparticle scenario, it happens at tree level and its contribution
may be sizable for practical measurement. Moreover, the BESIII will offer the
largest database on which makes more accurate measurements possible.
Furthermore, for such purely leptonic decays background is relatively low and
signal would be cleaner. Our work carefully investigates the possibility of
observing such processes from both theoretical and experimental aspects.Comment: 11 pages, 2 figures, revised version for publicatio
Final State Interactions in
It is believed that the production rate of is almost
solely determined by final state interactions (FSI) and hence provides an ideal
place to test FSI models. Here we examine model calculations of the
contributions from s-channel resonance and t-channel exchange to
the FSI effects in . The contribution from s-channel
is sma The results from
two methods are roughly consistent with each other and can reproduce the large
rate of reasonably well$Comment: Latex, 16 pages, with 2 figure
Spin-Polarized Transport Across an LaSrMnO/YBaCuO Interface: Role of Andreev Bound States
Transport across an
LaSr_{3}/YBa_{3}_{7}_{3}$/YBCO and Ag/YBCO. In all cases, YBCO is used as bottom layer to
eliminate the channel resistance and to minimize thermal effects. The observed
differential conductance re ects the role of Andreev bound states in a-b
planes, and brings out for the first time the suppression of such states by the
spin-polarized transport across the interface. The theoretical analysis of the
measured data reveals decay of the spin polarization near the LSMO surface with
temperature, consistent with the reported photoemission data.Comment: 5 pages LaTeX, 3 eps figures included, accepted by Physical Review
Charmless Three-Body Baryonic B Decays
Motivated by recent data on B-> p pbar K decay, we study various charmless
three-body baryonic B decay modes, including Lambda pbar pi, Sigma0 pbar pi, p
pbar pi, p pbar Kbar0, in a factorization approach. These modes have rates of
order 10^{-6}. There are two mechanisms for the baryon pair production,
current-produced and transition. The behavior of decay spectra from these
baryon production mechanisms can be understood by using QCD counting rules.
Predictions on rates and decay spectra can be checked in the near future.Comment: 26 pages, 9 figures; version to appear in Phys. Rev.
A note on Friedmann equation of FRW universe in deformed Horava-Lifshitz gravity from entropic force
With entropic interpretation of gravity proposed by Verlinde, we obtain the
Friedmann equation of the Friedmann-Robertson-Walker universe for the deformed
Ho\v{r}ava-Lifshitz gravity. It is shown that, when the parameter of
Ho\v{r}ava-Lifshitz gravity , the modified Friedmann
equation will go back to the one in Einstein gravity. This results may imply
that the entropic interpretation of gravity is effective for the deformed
Ho\v{r}ava-Lifshitz gravity.Comment: 9 pages, no figure
Cosmic Evolution in Brans-Dicke Chameleon Cosmology
We have investigated the Brans-Dicke Chameleon theory of gravity and obtained
exact solutions of the scale factor , scalar field , an
arbitrary function which interact with the matter Lagrangian in the
action of the Brans-Dicke Chameleon theory and potential for
different epochs of the cosmic evolution. We plot the functions ,
, and for different values of the Brans-Dicke
parameter. In our models, there is no accelerating solution, only decelerating
one with . The physical cosmological distances have been investigated
carefully. Further the statefinder parameters pair and deceleration parameter
are discussed.Comment: To be appear in "The European Physical Journal - Plus (EPJ
Plus)",Extended version,15 pages, 17eps figure
Grain boundary effects on magnetotransport in bi-epitaxial films of LaSrMnO
The low field magnetotransport of LaSrMnO (LSMO) films
grown on SrTiO substrates has been investigated. A high qualtity LSMO film
exhibits anisotropic magnetoresistance (AMR) and a peak in the
magnetoresistance close to the Curie temperature of LSMO. Bi-epitaxial films
prepared using a seed layer of MgO and a buffer layer of CeO display a
resistance dominated by grain boundaries. One film was prepared with seed and
buffer layers intact, while a second sample was prepared as a 2D square array
of grain boundaries. These films exhibit i) a low temperature tail in the low
field magnetoresistance; ii) a magnetoconductance with a constant high field
slope; and iii) a comparably large AMR effect. A model based on a two-step
tunneling process, including spin-flip tunneling, is discussed and shown to be
consistent with the experimental findings of the bi-epitaxial films.Comment: REVTeX style; 14 pages, 9 figures. Figure 1 included in jpeg format
(zdf1.jpg); the eps was huge. Accepted to Phys. Rev.
Magnetoresistance and spin-transfer torque in magnetic tunnel junctions
We comment on both recent progress and lingering puzzles related to research
on magnetic tunnel junctions (MTJs). MTJs are already being used in
applications such as magnetic-field sensors in the read heads of disk drives,
and they may also be the first device geometry in which spin-torque effects are
applied to manipulate magnetic dynamics, in order to make nonvolatile magnetic
random access memory. However, there remain many unanswered questions about
such basic properties as the magnetoresistance of MTJs, how their properties
change as a function of tunnel-barrier thickness and applied bias, and what are
the magnitude and direction of the spin-transfer-torque vector induced by a
tunnel current.Comment: 37 pages, 2 figures. Contribution to a collection of "Current
Perspectives" articles on spin transfer torque now available in the Journal
of Magnetism and Magnetic Material
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