1,178 research outputs found
Condensation of Silica Nanoparticles on a Phospholipid Membrane
The structure of the transient layer at the interface between air and the
aqueous solution of silica nanoparticles with the size distribution of
particles that has been determined from small-angle scattering has been studied
by the X-ray reflectometry method. The reconstructed depth profile of the
polarizability of the substance indicates the presence of a structure
consisting of several layers of nanoparticles with the thickness that is more
than twice as large as the thickness of the previously described structure. The
adsorption of 1,2-distearoyl-sn-glycero-3-phosphocholine molecules at the
hydrosol/air interface is accompanied by the condensation of anion silica
nanoparticles at the interface. This phenomenon can be qualitatively explained
by the formation of the positive surface potential due to the penetration and
accumulation of Na+ cations in the phospholipid membrane.Comment: 7 pages, 5 figure
The effective action and equations of motion of curved local and global vortices: Role of the field excitations
The effective actions for both local and global curved vortices are derived,
based on the derivative expansion of the corresponding field theoretic actions
of the nonrelativistic Abelian Higgs and Goldstone models. The role of
excitations of the modulus and the phase of the scalar field and of the gauge
field (the Bogolyubov-Anderson mode) emitted and reabsorbed by vortices is
elucidated. In case of the local (gauge) magnetic vortex, they are necessary
for cancellation of the long distance divergence when using the transverse form
of the electric gauge field strength of the background field. In case of global
vortex taking them into account results in the Greiter-Wilczek-Witten form of
the effective action for the Goldstone mode. The expressions for transverse
Magnus-like force and the vortex effective mass for both local and global
vortices are found. The equations of motion of both type of vortices including
the terms due to the field excitations are obtained and solved in cases of
large and small contour displacements.Comment: 16 pages, no figures; accepted for publication in Int. Journ. Mod.
Phys.
Equilibrium properties of the mixed state in superconducting niobium in a transverse magnetic field: Experiment and theoretical model
Equilibrium magnetic properties of the mixed state in type-II superconductors
were measured with high purity bulk and film niobium samples in parallel and
perpendicular magnetic fields using dc magnetometry and scanning Hall-probe
microscopy. Equilibrium magnetization data for the perpendicular geometry were
obtained for the first time. It was found that none of the existing theories is
consistent with these new data. To address this problem, a theoretical model is
developed and experimentally validated. The new model describes the mixed state
in an averaged limit, i.e. %without detailing the samples' magnetic structure
and therefore ignoring interactions between vortices. It is quantitatively
consistent with the data obtained in a perpendicular field and provides new
insights on properties of vortices. % and the entire mixed state. At low values
of the Ginzburg-Landau parameter, the model converts to that of Peierls and
London for the intermediate state in type-I superconductors. It is shown that
description of the vortex matter in superconductors in terms of a 2D gas is
more appropriate than the frequently used crystal- and glass-like scenarios.Comment: 8 pages, 9 figure
Gauge vortex dynamics at finite mass of bosonic fields
The simple derivation of the string equation of motion adopted in the
nonrelativistic case is presented, paying the special attention to the effects
of finite masses of bosonic fields of an Abelian Higgs model. The role of the
finite mass effects in the evaluation of various topological characteristics of
the closed strings is discussed. The rate of the dissipationless helicity
change is calculated. It is demonstrated how the conservation of the sum of the
twisting and writhing numbers of the string is recovered despite the changing
helicity.Comment: considerably revised to include errata to journal versio
First principle computation of stripes in cuprates
We present a first principle computation of vertical stripes in
within the LDA+U method. We find that Cu centered
stripes are unstable toward O centered stripes. The metallic core of the stripe
is quite wide and shows reduced magnetic moments with suppressed
antiferromagnetic (AF) interactions. The system can be pictured as alternating
metallic and AF two-leg ladders the latter with strong AF interaction and a
large spin gap. The Fermi surface shows warping due to interstripe
hybridization. The periodicity and amplitude of the warping is in good
agreement with angle resolved photoemission experiment. We discuss the
connection with low-energy theories of the cuprates.Comment: 5 pages,4 figure
Sustainable Energy for Smart City
The article presents the results of a study of structural changes in the energy sector serving digital technologies for the urban environment of the future that is being created now. The study considers country-specific factors and problems of ensuring the sustainability of heat and power supply.
The authors look at the priority areas of a new phase of electrification aimed at the development of advanced energy-saving smart technologies, electric transport, electric cars and appropriate energy and utility infrastructure. The case is studied of developing engineering, technical, organizational and economic solutions when overhauling the heat supply system in a ‘smart’ residential district of Yekaterinburg, one of Russia’s megalopolises, that is being designed and constructed on the basis of the principles of intelligent engineering infrastructure.The work was supported by Act 211 of the Government of the Russian Federation, contract 02.A03.21.0006
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