332 research outputs found
Initiation and blocking of the action potential in the axon in weak ultrasonic or microwave fields
In this paper, we analyze the effect of the redistribution of the
transmembrane ion channels in the axon caused by longitudinal acoustic
vibrations of the membrane. These oscillations can be excited by an external
source of ultrasound and weak microwave radiation interacting with the charges
sitting on the surface of the lipid membrane. It is shown, using the
Hodgkin-Huxley model of the axon, that the density redistribution of
transmembrane sodium channels may reduce the threshold of the action potential,
up to its spontaneous initiation. At the significant redistribution of sodium
channels in membrane, the rarefaction zones of the transmembrane channels
density are formed, blocking the propagation of the action potential. Blocking
the action potential propagation along the axon is shown to cause anestesia in
the example case of a squid axon. Various approaches to experimental
observation of the effects considered in this paper are discussed
Non-thermal influence of a weak microwave on nerve fiber activity
This paper presents a short selective review of the non-thermal weak
microwave field impact on a nerve fiber. The published results of recent
experiments are reviewed and analyzed. The theory of the authors is presented,
according to which there are strongly pronounced resonances in the range of
about 30-300 GHz associated with the excitation of ultrasonic vibrations in the
membrane as a result of interactions with the microwave radiation. These forced
vibrations create acoustic pressure, which may lead to the redistribution of
the protein transmembrane channels, thus changing the threshold of the action
potential excitation in the axons of the neural network. The problem of surface
charge on the bilayer lipid membrane of the nerve fiber is discussed. Various
experiments for observing the effects considered are also discussed.Comment: arXiv admin note: text overlap with arXiv:1309.594
Cavitation nanopore in the dielectric fluid in the inhomogeneous, pulsed electric fields
This paper discusses the nanopores emerging and developing in a liquid
dielectric under the action of the ponderomotive electrostrictive forces in a
nonuniform electric field. It is shown that the gradient of the electric field
in the vicinity of the rupture (cavitation nanopore) substantially increases
and determines whether the rupture grows or collapses. The cavitation rupture
in the liquid (nanopore) tends to stretch along the lines of the original
field. The mechanism of the breakdown associated with the generation of
secondary ruptures in the vicinity of the poles of the nanopore is proposed.
The estimations of the extension time for nanopore in water and oil (polar and
nonpolar liquids, respectively) are presented. A new mechanism of nano- and
subnanosecond breakdown in the insulating (transformer) oil that can be
realized in the vicinity of water microdroplets in modern nanosecond
high-voltage devices is considere
Initial stage of cavitation in liquids and its observation by Rayleigh scattering
A theory is developed for the initial stage of cavitation in the framework of
Zel'dovich-Fisher theory of nucleation in the field of negative pressure, while
taking into account the surface tension dependence on the nanopore radius. A
saturation mechanism is proposed that limits the exponential dependence of the
nucleation rate on the energy required to create nanopores. An estimate of the
saturated density of nanopores at the nucleation stage is obtained. It is shown
that Rayleigh scattering can detect nanopores arising at the initial stage of
cavitation development
Cavitation near the oscillating piezoelectric plate in water
It is known that gas bubbles on the surface bounding a fluid flow can change
the coefficient of friction and affect the parameters of the boundary layer. In
this paper, we propose a method that allows us to create, in the near-wall
region, a thin layer of liquid filled with bubbles. It will be shown that if
there is an oscillating piezoelectric plate on the surface bounding a liquid,
then, under certain conditions, cavitation develops in the boundary layer. The
relationship between the parameters of cavitation and the characteristics of
the piezoelectric plate oscillations is obtained. Possible applications are
discussed
Dielectric Fluid in Inhomogeneous Pulsed Electric Field
We consider the dynamics of a compressible fluid under the influence of
electrostrictive ponderomotive forces in strong inhomogeneous nonstationary
electric fields. It is shown that if the fronts of the voltage rise at a sharp,
needle-like electrode are rather steep (less than or about nanoseconds), and
the region of negative pressure arises, which can reach values at which the
fluid loses its continuity with the formation of cavitation ruptures. If the
voltage on the electrode is not large enough or the front is flatter, the
cavitation in the liquid does not occur. However, a sudden shutdown of the
field results in a reverse flow of liquid from the electrode, which leads to
appearance of negative pressure, and, possibly, cavitation
Correlation of action potentials in adjacent neurons
A possible mechanism for the synchronization of action potential propagation
along a bundle of neurons (ephaptic coupling) is considered. It is shown that
this mechanism is similar to the salutatory conduction of the action potential
between the nodes of Ranvier in myelinated axons. The proposed model allows us
to estimate the scale of the correlation, i.e., the distance between neurons in
the nervous tissue, wherein their synchronization becomes possible. The
possibility for experimental verification of the proposed model of
synchronization is discussed
The surface charge of a cell lipid membrane
In this paper the problem of surface charge of the lipid membrane immersed in
the physiological solution is considered. It is shown that both side of the
bilayer phospholipid membrane surface are negatively charged. A self-consistent
model of the potential in solution is developed, and a stationary charge
density on the membrane surface is found. It is shown that the ions of the
surface charge are in a relatively deep (as compared to kBT) potential wells,
which are localized near the dipole heads of phospholipid membrane. It makes
impossible for ions to slip along the membrane surface. Simple experiments for
verifying the correctness of the considered model are proposed. A developed
approach can be used for estimations of the surface charges on the outer and
inner membrane of the cell
Andreev Blockade in a Double Quantum Dot with a Superconducting Lead
A normal metal source reservoir can load two electrons onto a double quantum
dot in the spin-triplet configuration. We show that if the drain lead of the
dot is a spin-singlet superconductor, these electrons cannot form a Cooper pair
and are blockaded on the double dot. We call this phenomenon Andreev blockade
because it arises due to suppressed Andreev reflections. We identify transport
characteristics unique to Andreev blockade. Most significantly, it occurs for
any occupation of the dot adjacent to the superconductor, in contrast with the
well-studied Pauli blockade which requires odd occupations. Andreev blockade is
lifted if quasiparticles are allowed to enter the superconducting lead, but it
should be observable in the hard gap superconductor-semiconductor devices.
Andreev blockade should be considered in the design of topological quantum
circuits, hybrid quantum bits and quantum emulators.Comment: 5 pages + supplemen
Amplitude / Higgs Modes in Condensed Matter Physics
The order parameter and its variations in space and time in many different
states in condensed matter physics at low temperatures are described by the
complex function . These states include superfluids,
superconductors, and a subclass of antiferromagnets and charge-density waves.
The collective fluctuations in the ordered state may then be categorized as
oscillations of phase and amplitude of . The phase
oscillations are the {\it Goldstone} modes of the broken continuous symmetry.
The amplitude modes, even at long wavelengths, are well defined and decoupled
from the phase oscillations only near particle-hole symmetry, where the
equations of motion have an effective Lorentz symmetry as in particle physics,
and if there are no significant avenues for decay into other excitations. They
bear close correspondence with the so-called {\it Higgs} modes in particle
physics, whose prediction and discovery is very important for the standard
model of particle physics. In this review, we discuss the theory and the
possible observation of the amplitude or Higgs modes in condensed matter
physics -- in superconductors, cold-atoms in periodic lattices, and in uniaxial
antiferromagnets. We discuss the necessity for at least approximate
particle-hole symmetry as well as the special conditions required to couple to
such modes because, being scalars, they do not couple linearly to the usual
condensed matter probes.Comment: 39 pages, 12 figures. Replaced with published version; Annual Reviews
of Condensed Matter Physics Volume 6 (2015
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