7,535 research outputs found
Structure formation in electromagnetically driven granular media
We report structure formation in submonolayers of magnetic microparticles
subjected to periodic electrostatic and magnetic excitations. Depending on the
excitation parameters, we observe the formation of a rich variety of
structures: clusters, rings, chains, and networks. The growth dynamics and
shapes of the structures are strongly dependent on the amplitude and frequency
of the external magnetic field. We find that for pure ac magnetic driving at
low densities of particles, the low-frequency magnetic excitation favors
clusters while high frequency excitation favors chains and net-like structures.
An abrupt phase transition from chains to a network phase was observed for a
high density of particles.Comment: 4 pages, 5 figure
An increase in under hydrostatic pressure in the superconducting doped topological insulator NbBiSe
We report an unexpected positive hydrostatic pressure derivative of the
superconducting transition temperature in the doped topological insulator \NBS
via SQUID magnetometry in pressures up to 0.6 GPa. This result is contrary
to reports on the homologues \CBS and \SBS where smooth suppression of is
observed. Our results are consistent with recent Ginzburg-Landau theory
predictions of a pressure-induced enhancement of in the nematic
multicomponent state proposed to explain observations of rotational
symmetry breaking in doped BiSe superconductors.Comment: 5 pages, 5 figure
Fokker-Planck equation with variable diffusion coefficient in the Stratonovich approach
We consider the Langevin equation with multiplicative noise term which
depends on time and space. The corresponding Fokker-Planck equation in
Stratonovich approach is investigated. Its formal solution is obtained for an
arbitrary multiplicative noise term given by , and the
behaviors of probability distributions, for some specific functions of %
, are analyzed. In particular, for , the physical
solutions for the probability distribution in the Ito, Stratonovich and
postpoint discretization approaches can be obtained and analyzed.Comment: 6 pages in LATEX cod
Design of dry powder formulations of pH responsive peptide/plasmid DNA complexes for pulmonary delivery
Poster Presentation: no. 13PS50Respiratory diseases are substantial public health problems around the world. Recently, nucleic acid was developed as a potential therapeutic strategy to tackle a series of lung diseases. Delivery still poses one of the major challenges for their clinical application. pH responsive peptides containing either histidine or derivatives of 2,3-diaminopropionic acid (Dap) can mediate effective DNA transfection in lung epithelial cells with the latter remaining effective even in the presence of lung surfactant containing bronchoalveolar fluid (BALF), which make them promising vectors for delivering therapeutic nucleic acid to the airways .....published_or_final_versio
Longitudinal Current Dissipation in Bose-glass Superconductors
A scaling theory of vortex motion in Bose glass superconductors with currents
parallel to the common direction of the magnetic field and columnar defects is
presented. Above the Bose-glass transition the longitudinal DC resistivity
vanishes much faster than the
corresponding transverse resistivity , thus {\it reversing} the usual anisotropy of electrical transport in
the normal state of layered superconductors. In the presence of a current at an angle with the common field and columnar defect axis, the
electric field angle approaches as .
Scaling also predicts the behavior of penetration depths for the AC currents as
, and implies a {\it jump discontinuity} at in
the superfluid density describing transport parallel to the columns.Comment: 5 pages, revte
Absence of the Transition into Abrikosov Vortex State of Two-Dimensional Type-II Superconductor with Weak Pinning
The resistive properties of thin amorphous NbO_{x} films with weak pinning
were investigated experimentally above and below the second critical field
H_{c2}. As opposed to bulk type II superconductors with weak pinning where a
sharp change of resistive properties at the transition into the Abrikosov state
is observed at H_{c4}, some percent below H_{c2} (V.A.Marchenko and
A.V.Nikulov, 1981), no qualitative change of resistive properties is observed
down to a very low magnetic field, H_{c4} < 0.006 H_{c2}, in thin films with
weak pinning. The smooth dependencies of the resistivity observed in these
films can be described by paraconductivity theory both above and below H_{c2}.
This means that the fluctuation superconducting state without phase coherence
remains appreciably below H_{c2} in the two-dimensional superconductor with
weak pinning. The difference the H_{c4}/H_{c2} values, i.e. position of the
transition into the Abrikosov state, in three- and two-dimensional
superconductors conforms to the Maki-Takayama result 1971 year according to
which the Abrikosov solution 1957 year is valid only for a superconductor with
finite dimensions. Because of the fluctuation this solution obtained in the
mean field approximation is not valid in a relatively narrow region below
H_{c2} for bulk superconductors with real dimensions and much below H_{c2} for
thin films with real dimensions. The superconducting state without phase
coherence should not be identified with the mythical vortex liquid because the
vortex, as a singularity in superconducting state with phase coherence, can not
exist without phase coherence.Comment: 4 pages, 4 figure
Hall Anomaly and Vortex-Lattice Melting in Superconducting Single Crystal YBa2Cu3O7-d
Sub-nanovolt resolution longitudinal and Hall voltages are measured in an
ultra pure YBa2Cu3O7-d single crystal. The Hall anomaly and the first-order
vortex-lattice melting transition are observed simultaneously. Changes in the
dynamic behavior of the vortex solid and liquid are correlated with features of
the Hall conductivity sxy. With the magnetic field oriented at an angle from
the twin-boundaries, the Hall conductivity sharply decreases toward large
negative values at the vortex-lattice melting transition.Comment: 6 pages, 2 figures included, Postscript, to appear in Phys. Rev. Let
Ground-state fidelity of Luttinger liquids: A wave functional approach
We use a wave functional approach to calculate the fidelity of ground states
in the Luttinger liquid universality class of one-dimensional gapless quantum
many-body systems. The ground-state wave functionals are discussed using both
the Schrodinger (functional differential equation) formulation and a path
integral formulation. The fidelity between Luttinger liquids with Luttinger
parameters K and K' is found to decay exponentially with system size, and to
obey the symmetry F(K,K')=F(1/K,1/K') as a consequence of a duality in the
bosonization description of Luttinger liquids.Comment: 13 pages, IOP single-column format. Sec. 3 expanded with discussion
of short-distance cut-off. Some typos corrected. Ref. 44 in v2 is now
footnote 2 (moved by copy editor). Published versio
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