2,839 research outputs found
'Theory for the enhanced induced magnetization in coupled magnetic trilayers in the presence of spin fluctuations'
Motivated by recent experiments, the effect of the interlayer exchange
interaction on the magnetic properties of coupled Co/Cu/Ni
trilayers is studied theoretically. Here the Ni film has a lower Curie
temperature than the Co film in case of decoupled layers. We
show that by taking into account magnetic fluctuations the interlayer coupling
induces a strong magnetization for T\gtsim T_{C,\rm Ni} in the Ni film. For
an increasing the resonance-like peak of the longitudinal Ni
susceptibility is shifted to larger temperatures, whereas its maximum value
decreases strongly. A decreasing Ni film thickness enhances the induced Ni
magnetization for T\gtsim T_{C,\rm Ni}. The measurements cannot be explained
properly by a mean field estimate, which yields a ten times smaller effect.
Thus, the observed magnetic properties indicate the strong effect of 2D
magnetic fluctuations in these layered magnetic systems. The calculations are
performed with the help of a Heisenberg Hamiltonian and a Green's function
approach.Comment: 4 pages, 3 figure
Toward one-band superconductivity in MgB2
The two-gap model for superconductivity in MgB2 predicts that interband
impurity scattering should be pair breaking, reducing the critical temperature.
This is perhaps the only prediction of the model that has not been confirmed
experimentally. It was previously shown theoretically that common
substitutional impurities lead to negligible interband scattering - if the
lattice is assumed not to distort. Here we report theoretical results showing
that certain impurities can indeed produce lattice distortions sufficiently
large to create measurable interband scattering. On this basis, we predict that
isoelectronic codoping with Al and Na will provide a decisive test of the
two-gap model.Comment: 4 pages, 2 figures, to appear in Phys. Rev.
From tunneling to photoemission: correlating two spaces
Correlating the data measured by tunneling and photoemission spectroscopies
is a long-standing problem in condensed matter physics. The quasiparticle
interference, recently discovered in high-Tc cuprates, reveals a possibility to
solve this problem. Application of modern phase retrieval algorithms to Fourier
transformed tunneling data allows to recover the distribution of the
quasiparticle spectral weight in the reciprocal space of solids measured
directly by photoemission. This opens a direct way to unify these two powerful
techniques and may help to solve a number of problems related with space/time
inhomogeneities predicted in strongly correlated electron systems.Comment: more info at http://www.imp.kiev.ua/~kord/AC-ARPES/index.htm
Clones with finitely many relative R-classes
For each clone C on a set A there is an associated equivalence relation
analogous to Green's R-relation, which relates two operations on A iff each one
is a substitution instance of the other using operations from C. We study the
clones for which there are only finitely many relative R-classes.Comment: 41 pages; proofs improved, examples adde
Two-loop approximation in the Coulomb blockade problem
We study Coulomb blockade (CB) oscillations in the thermodynamics of a
metallic grain which is connected to a lead by a tunneling contact with a large
conductance in a wide temperature range, ,
where is the charging energy. Using the instanton analysis and the
renormalization group we obtain the temperature dependence of the amplitude of
CB oscillations which differs from the previously obtained results. Assuming
that at the oscillation amplitude weakly depends on
temperature we estimate the magnitude of CB oscillations in the ground state
energy as .Comment: 10 pages, 3 figure
Electromigration of Single-Layer Clusters
Single-layer atom or vacancy clusters in the presence of electromigration are
studied theoretically assuming an isotropic medium. A variety of distinctive
behaviors distinguish the response in the three standard limiting cases of
periphery diffusion (PD), terrace diffusion (TD), and evaporation-condensation
(EC). A general model provides power laws describing the size dependence of the
drift velocity in these limits, consistent with established results in the case
of PD. The validity of the widely used quasistatic limit is calculated. Atom
and vacancy clusters drift in opposite directions in the PD limit but in the
same direction otherwise. In absence of PD, linear stability analysis reveals a
new type of morphological instability, not leading to island break-down. For
strong electromigration, Monte Carlo simulations show that clusters then
destabilize into slits, in contrast to splitting in the PD limit.
Electromigration affects the diffusion coefficient of the cluster and
morphological fluctuations, the latter diverging at the instability threshold.
An instrinsic attachment-detachment bias displays the same scaling signature as
PD in the drift velocity.Comment: 11 pages, 4 figure
Magnetically Controllable Polymer Nanotubes from a Cyclized Crosslinker for Site-Specific Delivery of Doxorubicin
Externally controlled site specific drug delivery could potentially provide a means of reducing drug related side effects whilst maintaining, or perhaps increasing therapeutic efficiency. The aim of this work was to develop a nanoscale drug carrier, which could be loaded with an anti-cancer drug and be directed by an external magnetic field. Using a single, commercially available monomer and a simple one-pot reaction process, a polymer was synthesized and crosslinked within the pores of an anodized aluminum oxide template. These polymer nanotubes (PNT) could be functionalized with iron oxide nanoparticles for magnetic manipulation, without affecting the large internal pore, or inherent low toxicity. Using an external magnetic field the nanotubes could be regionally concentrated, leaving areas devoid of nanotubes. Lastly, doxorubicin could be loaded to the PNTs, causing increased toxicity towards neuroblastoma cells, rendering a platform technology now ready for adaptation with different nanoparticles, degradable pre-polymers and various therapeutics
First Principles Calculation of Elastic Properties of Solid Argon at High Pressures
The density and the elastic stiffness coefficients of fcc solid argon at high
pressures from 1 GPa up to 80 GPa are computed by first-principles
pseudopotential method with plane-wave basis set and the generalized gradient
approximation (GGA). The result is in good agreement with the experimental
result recently obtained with the Brillouin spectroscopy by Shimizu et al.
[Phys. Rev. Lett. 86, 4568 (2001)]. The Cauchy condition was found to be
strongly violated as in the experimental result, indicating large contribution
from non-central many-body force. The present result has made it clear that the
standard density functional method with periodic boundary conditions can be
successfully applied for calculating elastic properties of rare gas solids at
high pressures in contrast to those at low pressures where dispersion forces
are important.Comment: 4 pages, 5 figures, submitted to PR
Heavy ion event generator HYDJET++ (HYDrodynamics plus JETs)
HYDJET++ is a Monte-Carlo event generator for simulation of relativistic
heavy ion AA collisions considered as a superposition of the soft, hydro-type
state and the hard state resulting from multi-parton fragmentation. This model
is the development and continuation of HYDJET event generator (Lokhtin &
Snigirev, 2006, EPJC, 45, 211). The main program is written in the
object-oriented C++ language under the ROOT environment. The hard part of
HYDJET++ is identical to the hard part of Fortran-written HYDJET and it is
included in the generator structure as a separate directory. The soft part of
HYDJET++ event is the "thermal" hadronic state generated on the chemical and
thermal freeze-out hypersurfaces obtained from the parameterization of
relativistic hydrodynamics with preset freeze-out conditions. It includes the
longitudinal, radial and elliptic flow effects and the decays of hadronic
resonances. The corresponding fast Monte-Carlo simulation procedure, C++ code
FAST MC (Amelin et al., 2006, PRC, 74, 064901; 2008, PRC, 77, 014903) is
adapted to HYDJET++. It is designed for studying the multi-particle production
in a wide energy range of heavy ion experimental facilities: from FAIR and NICA
to RHIC and LHC.Comment: 44 pages including 6 figures as EPS-files; prepared using LaTeX
package for publication in Computer Physics Communication
Organogenesis of Phaseolus angularis L.: high efficiency of adventitious shoot regeneration from etiolated seedlings in the presence of N6-benzylaminopurine and thidiazuron
A step-wise procedure for the regeneration of fertile plants by organogenesis from cultures of the economically important Phaseolus angularis L., cultivars: KS-6, KS-7 and KS-8 using etiolated seedlings was established. Pre-culture of 5-day old seedling explants with MS (Murashige and Skoog (1962) Physiol Plant 15:473-493) + B-5-vitamins (Gamborg et al. (1968) Exp Cell Res 50:151-158) liquid medium containing either 5.0 mu M TDZ or 5.0 mu M BAP under dark condition was essential for organogenesis. Bud growth and shoot multiplication were stimulated by reducing the BAP concentrations from 5.0 to 2.5 mu M after 3 weeks. The maximum frequency of shoot induction was 65.2% (33.8 +/- 2.54 shoots/explant) in cultivar KS-8 followed by KS-7 34.6% (23.4 +/- 1.91 shoots/explant) and KS-6 30.6% (21.2 +/- 2.28 shoots/explant). The multiplied buds elongated after transferring to solid MSB5 medium supplemented with 4.0 mu M GA(3), 12.5 mu M AgNO3 and 0.4 mu M IBA. Up to 98% rooting efficiency of was obtained when the shoots were pulse-treated with liquid medium containing 4.5 mu M IBA for 10 min. The rooted plantlets were transferred to pots in the greenhouse, where they grew, mature, flowered and bared pod normally. The efficient shoot bud induction capability was found to be cultivar dependent. All the three cultivars tested formed multiple shoots. This efficient and rapid regeneration system may also be helpful for Agrobacterium- or particle gun-mediated transformation for this important legume crop
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