384 research outputs found
Effect of ferromagnetic film thickness on magnetoresistance of thin-film superconductor-ferromagnet hybrids
We study the influence of the thickness Df of the plain ferromagnetic (F)
film on the electrical resistance of the flux-coupled hybrids, consisting of
superconducting (S) Al film and multilayer [Co/Pt] F film with out-of-plain
magnetization. The behavior of such hybrids at high and low temperatures is
found to be different: the nucleation of superconductivity at high temperatures
is governed mainly by the typical lateral dimensions of the magnetic domains,
while low temperature properties are determined by topology of the magnetic
template. We show that an increase in the Df value leads to a broadening of the
field- and temperature intervals where non-monotonous dependence of the
superconducting critical temperature Tc on the applied magnetic field H is
observed (for demagnetized F films). Further increase in the Df value results
in a global suppression of superconductivity. Thus, we determined an optimal
thickness, when the non-monotonous dependence Tc(H) can be observed in rather
broad T and H range, what can be interesting for further studies of the
localized superconductivity in planar Al-based S/F hybrids and for development
of the devices which can exploit the localized superconductivity.Comment: 10 pages, 9 figure
Sonoluminescence and collapse dynamics of multielectron bubbles in helium
Multielectron bubbles (MEBs) differ from gas-filled bubbles in that it is the
Coulomb repulsion of a nanometer thin layer of electrons that forces the bubble
open rather than the pressure of an enclosed gas. We analyze the implosion of
MEBs subjected to a pressure step, and find that despite the difference in the
underlying processes the collapse dynamics is similar to that of gas-filled
bubbles. When the MEB collapses, the electrons inside it undergo strong
accelerations, leading to the emission of radiation. This type of
sonoluminescence does not involve heating and ionisation of any gas inside the
bubble. We investigate the conditions necessary to obtain sonoluminescence from
multielectron bubbles and calculate the power spectrum of the emitted
radiation.Comment: 6 figure
Charged-Surface Instability Development in Liquid Helium; Exact Solutions
The nonlinear dynamics of charged-surface instability development was
investigated for liquid helium far above the critical point. It is found that,
if the surface charge completely screens the field above the surface, the
equations of three-dimensional (3D) potential motion of a fluid are reduced to
the well-known equations describing the 3D Laplacian growth process. The
integrability of these equations in 2D geometry allows the analytic description
of the free-surface evolution up to the formation of cuspidal singularities at
the surface.Comment: latex, 5 pages, no figure
Stability of multi-electron bubbles in liquid helium
The stability of multi-electron bubbles in liquid helium is investigated
theoretically. We find that multi-electron bubbles are unstable against fission
whenever the pressure is positive. It is shown that for moving bubbles the
Bernoulli effect can result in a range of pressures over which the bubbles are
stable.Comment: 7 pages, 5 figure
Amplification of Fluctuations in Unstable Systems with Disorder
We study the early-stage kinetics of thermodynamically unstable systems with
quenched disorder. We show analytically that the growth of initial fluctuations
is amplified by the presence of disorder. This is confirmed by numerical
simulations of morphological phase separation (MPS) in thin liquid films and
spinodal decomposition (SD) in binary mixtures. We also discuss the
experimental implications of our results.Comment: 15 pages, 4 figure
WRAPPING AROUND THE RECONSTRUCTION PLATE WITH A PECTORALIS MUSCLE FLAP IN MANDIBULAR REPAIR AFTER SEGMENTAL RESECTION
The paper gives information on the proposed procedure for wrapping around the reconstruction plate with a pectoralis muscle flap in case of segmental resection of the lower jaw and recovery of its continuity with a titanium plate if there is a sufficient area of integuments (skin and mucosa) and soft tissue shortage
Microwave saturation of the Rydberg states of electrons on helium
We present measurements of the resonant microwave excitation of the Rydberg
energy levels of surface state electrons on superfluid helium. The temperature
dependent linewidth agrees well with theoretical predictions and is very small
below 300 mK. Absorption saturation and power broadening were observed as the
fraction of electrons in the first excited state was increased to 0.49, close
to the thermal excitation limit of 0.5. The Rabi frequency was determined as a
function of microwave power. The high values of the ratio of the Rabi frequency
to linewidth confirm this system as an excellent candidate for creating qubits.Comment: 4 pages, 4 figure
A CASE OF SURGICAL TREATMENT FOR A PARATRACHEOSTOMIC RECURRENCE OF LARYNGEAL CANCER
The paper presents information on a case of successful repair with a pectoral musculocutaneous flap for a paratracheostomic recurrence of laryngeal cancer
Highly Stable, Water-Soluble CdSe/ZnS/CdS/ZnS Quantum Dots with Additional SiO2 shell
Quantum dots (QDs) are fluorescent nanocrystals extensively used today in research and applications. They attract much interest due to the high photostability and fluorescence quantum yields close to 100%. The best QDs are made by synthesis in organic media, and they have to be transferred into aqueous solutions if biomedical applications are concerned. An advanced method for rendering QDs water-soluble is to coat them with hydrophilic SiO2 -layer. However, growing a silica shell with a predetermined thickness is a problem, because uncertain values of the molar extinction coefficients (ε) of core/shell QDs made it impossible to calculate precise yields of the chemical reactions involved. Here we suggest an approach to solving this problem by constructing the structural models of per se and silica-coated QDs followed by measuring ε in a course of the QD synthesis, thus carrying out precise quantitative reactions. Proceeding in such a way, we prepared the CdSe/ZnS/CdS/ZnS QDs with the structure predicted by the model and coated by silica shell. Prepared QDs are characterized by a narrow size distribution and the same fluorescence parameters as the original QDs in the organic medium. Developed approach permitted efficient QDs water-solubilisation and preparation of stable nanoparticles for plethora of biomedical applications.
Keywords: Quantum dots, QD, silica shell, core-shel
Applying an improved phonon confinement model to the analysis of Raman spectra of germanium nanocrystals
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