4,281 research outputs found
Microencapsulation technology by nature: Cell derived extracellular vesicles with therapeutic potential
Cell derived extracellular vesicles are submicron structures surrounded by phospholipid bilayer and released by both prokaryotic
and eukaryotic cells. The sizes of these vesicles roughly fall into the size ranges of microbes, and they represent efficient delivery
platforms targeting complex molecular information to professional antigen presenting cells. Critical roles of these naturally formulated
units of information have been described in many physiological and pathological processes. Extracellular vesicles are not only
potential biomarkers and possible pathogenic factors in numerous diseases, but they are also considered as emerging therapeutic
targets and therapeutic vehicles. Strikingly, current drug delivery systems, designed to convey therapeutic proteins and peptides
(such as liposomes), show many similarities to extracellular vesicles. Here we review some aspects of therapeutic implementation
of natural, cell-derived extracellular vesicles in human diseases. Exploration of molecular and functional details of extracellular
vesicle release and action may provide important lessons for the design of future drug delivery systems
Dual-frequency ferromagnetic resonance
We describe a new experimental technique to investigate coupling effects
between different layers or modes in ferromagnetic resonance (FMR). Dual FMR
frequencies are excited (2-8 GHz) simultaneously and detected selectively in a
broadband RF circuit, using lock-in amplifier detection at separate modulation
frequencies.Comment: 4 pages, 4 figures, accepted by "Review of Scientific Instruments",
200
Current-spin coupling for ferromagnetic domain walls in fine wires
The coupling between a current and a domain wall is examined. In the presence
of a finite current and the absence of a potential which breaks the
translational symmetry, there is a perfect transfer of angular momentum from
the conduction electrons to the wall. As a result, the ground state is in
uniform motion. This remains the case when relaxation is accounted for. This is
described by, appropriately modified, Landau-Lifshitz-Gilbert equations.Comment: 4 pqges, no figure
Bose Einstein Condensation of incommensurate solid 4He
It is pointed out that simulation computation of energy performed so far
cannot be used to decide if the ground state of solid 4He has the number of
lattice sites equal to the number of atoms (commensurate state) or if it is
different (incommensurate state). The best variational wave function, a shadow
wave function, gives an incommensurate state but the equilibrium concentration
of vacancies remains to be determined. In order to investigate the presence of
a supersolid phase we have computed the one--body density matrix in solid 4He
for the incommensurate state by means of the exact Shadow Path Integral Ground
State projector method. We find a vacancy induced Bose Einstein condensation of
about 0.23 atoms per vacancy at a pressure of 54 bar. This means that bulk
solid 4He is supersolid at low enough temperature if the exact ground state is
incommensurate.Comment: 5 pages, 2 figure
A Fresh Look at Entropy and the Second Law of Thermodynamics
This paper is a non-technical, informal presentation of our theory of the
second law of thermodynamics as a law that is independent of statistical
mechanics and that is derivable solely from certain simple assumptions about
adiabatic processes for macroscopic systems. It is not necessary to assume
a-priori concepts such as "heat", "hot and cold", "temperature". These are
derivable from entropy, whose existence we derive from the basic assumptions.
See cond-mat/9708200 and math-ph/9805005.Comment: LaTex file. To appear in the April 2000 issue of PHYSICS TODA
Controlled switching between paramagnetic and diamagnetic Meissner effect in Pb/Co nanocomposites
A hybrid system which consists of a superconducting (SC) Pb film (100 nm
thickness) containing 1 vol% single domain ferromagnetic (FM) Co
particles of mean-size 4.5 nm reveal unusual magnetic properties: (i) a
controlled switching between the usual diamagnetic and the unusual paramagnetic
Meissner effect in field cooling as well as in zero-field cooling experiments
(ii) amplification of the positive magnetization when the sample enters the SC
state below T. These experimental findings can be explained by the
formation of spontaneous vortices and the possible alignment of these vortices
due to the foregoing alignment of the Co particle FM moments by an external
magnetic field.Comment: 5 pages, 3 figure
Unidimensional model of the ad-atom diffusion on a substrate submitted to a standing acoustic wave I. Derivation of the ad-atom motion equation
The effect of a standing acoustic wave on the diffusion of an ad-atom on a
crystalline surface is theoretically studied. We used an unidimensional space
model to study the ad-atom+substrate system. The dynamic equation of the
ad-atom, a Generalized Langevin equation, is analytically derived from the full
Hamiltonian of the ad-atom+substrate system submitted to the acoustic wave. A
detailed analysis of each term of this equation, as well as of their
properties, is presented. Special attention is devoted to the expression of the
effective force induced by the wave on the ad-atom. It has essentially the same
spatial and time dependences as its parent standing acoustic wave
Kondo Quantum Dots and the Novel Kondo-doublet interaction
We analyze the interactions between two Kondo Quantum Dots connected to a
Rashba-active Quantum Wire. We find that the Kondo-doublet interaction, at an
inter-dot distance of the order of the wire Fermi length, is over an order of
magnitude greater than the RKKY interaction. The effects induced on the
Kondo-doublet interaction by the wire spin-orbit coupling can be used to
control the Quantum Dots spin-spin correlation. These results imply that the
widely used assumption that the RKKY is the dominant interaction between
Anderson impurities must be revised.Comment: 4 pages, 4 figs, accepted for publication in PRL. title changed and
text polishe
Unconventional Hall effect in pnictides from interband interactions
We calculate the Hall transport in a multiband systems with a dominant
interband interaction between carriers having electron and hole character. We
show that this situation gives rise to an unconventional scenario, beyond the
Boltzmann theory, where the quasiparticle currents dressed by vertex
corrections acquire the character of the majority carriers. This leads to a
larger (positive or negative) Hall coefficient than what expected on the basis
of the carrier balance, with a marked temperature dependence. Our results
explain the puzzling measurements in pnictides and they provide a more general
framework for transport properties in multiband materials.Comment: 5 pages, 2 figure
Spin Polarization via Electron Tunneling through an Indirect-Gap Semiconductor Barrier
We study the spin dependent tunneling of electrons through a zinc-blende
semiconductor with the indirect X (or D) minimum serving as the tunneling
barrier. The basic difference between tunneling through the G vs. the X barrier
is the linear-k spin-orbit splitting of the two spin bands at the X point, as
opposed to the k3 Dresselhaus splitting at the G point. The linear coefficient
of the spin splitting b at the X point is computed for several semiconductors
using density-functional theory and the transport characteristics are
calculated using the barrier tunneling model. We show that both the
transmission coefficient as well as the spin polarization can be large,
suggesting the potential application of these materials as spin filters.Comment: 9 page
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