311 research outputs found
Mesoscopic field and current compensator based on a hybrid superconductor-ferromagnet structure
A rather general enhancement of superconductivity is demonstrated in a hybrid
structure consisting of submicron superconducting (SC) sample combined with an
in-plane ferromagnet (FM). The superconducting state resists much higher
applied magnetic fields for both perpendicular polarities, as applied field is
screened by the FM. In addition, FM induces (in the perpendicular direction to
its moment) two opposite current-flows in the SC plane, under and aside the
magnet, respectively. Due to the compensation effects, superconductivity
persists up to higher applied currents. With increasing current, the sample
undergoes SC-"resistive"-normal state transitions through a mixture of
vortex-antivortex and phase-slip phenomena.Comment: 4 pages, 5 figures, to appear in Phys. Rev. Let
Vertical pairing of identical particles suspended in the plasma sheath
It is shown experimentally that vertical pairing of two identical
microspheres suspended in the sheath of a radio-frequency (rf) discharge at low
gas pressures (a few Pa), appears at a well defined instability threshold of
the rf power. The transition is reversible, but with significant hysteresis on
the second stage. A simple model, which uses measured microsphere resonance
frequencies and takes into account besides Coulomb interaction between
negatively charged microspheres also their interaction with positive ion wake
charges, seems to explain the instability threshold quite well.Comment: 4 pages, 6 figures. to appear in Phys. Rev. Lett. 86, May 14th (2001
Nonlinear dynamics of large amplitude dust acoustic shocks and solitary pulses in dusty plasmas
We present a fully nonlinear theory for dust acoustic (DA) shocks and DA
solitary pulses in a strongly coupled dusty plasma, which have been recently
observed experimentally by Heinrich et al. [Phys. Rev. Lett. 103, 115002
(2009)], Teng et al. [Phys. Rev. Lett. 103, 245005 (2009)], and Bandyopadhyay
et al. [Phys. Rev. Lett. 101, 065006 (2008)]. For this purpose, we use a
generalized hydrodynamic model for the strongly coupled dust grains, accounting
for arbitrary large amplitude dust number density compressions and potential
distributions associated with fully nonlinear nonstationary DA waves.
Time-dependent numerical solutions of our nonlinear model compare favorably
well with the recent experimental works (mentioned above) that have reported
the formation of large amplitude non-stationary DA shocks and DA solitary
pulses in low-temperature dusty plasma discharges.Comment: 9 pages, 4 figures. To be published in Physical Review
Freezing and melting of 3D complex plasma structures under microgravity conditions driven by neutral gas pressure manipulation
Freezing and melting of large three-dimensional complex plasmas under
microgravity conditions is investigated. The neutral gas pressure is used as a
control parameter to trigger the phase changes: Complex plasma freezes (melts)
by decreasing (increasing) the pressure. Evolution of complex plasma structural
properties upon pressure variation is studied. Theoretical estimates allow us
to identify main factors responsible for the observed behavior.Comment: Phys. Rev. Lett. (in press); 4 pages, 4 figure
Fluid-solid phase transitions in 3D complex plasmas under microgravity conditions
Phase behavior of large three-dimensional complex plasma systems under
microgravity conditions onboard the International Space Station is
investigated. The neutral gas pressure is used as a control parameter to
trigger phase changes. Detailed analysis of structural properties and
evaluation of three different melting/freezing indicators reveal that complex
plasmas can exhibit melting by increasing the gas pressure. Theoretical
estimates of complex plasma parameters allow us to identify main factors
responsible for the observed behavior. The location of phase states of the
investigated systems on a relevant equilibrium phase diagram is estimated.
Important differences between the melting process of 3D complex plasmas under
microgravity conditions and that of flat 2D complex plasma crystals in ground
based experiments are discussed.Comment: 13 pages, 10 figures; submitted to Phys. Rev.
Unified analytical algorithm for identification of component composition of winemaking products
The article discusses a unified analytical algorithm for identification of component composition of winemaking products, established in the new national standard GOST R 59570-2021 «Winemaking products. Identification of component in terms of determination of the origin of ethanol and other compounds of physical-chemical composition». The standard provides modern scientific data on winemaking products, as well as data on natural, agrotechnical and technological factors that can impact the component composition of products to interpret the results of analytical evaluations. The article provides practical examples of use of analytical methods established in the standard for the study of winemaking products produced in Russia, Kazakhstan, Armenia and foreign countries
Current-voltage characteristics of quasi-one-dimensional superconductors: An S-curve in the constant voltage regime
Applying a constant voltage to superconducting nanowires we find that its
IV-characteristic exhibits an unusual S-behavior. This behavior is the direct
consequence of the dynamics of the superconducting condensate and of the
existence of two different critical currents: j_{c2} at which the pure
superconducting state becomes unstable and j_{c1}<j_{c2} at which the phase
slip state is realized in the system.Comment: 4 pages, 5 figures, replaced with minor change
Large Magnetoresistance Oscillations in Mesoscopic Superconductors Due to Current-Excited Moving Vortices
We show in the case of a superconducting Nb ladder that a mesoscopic
superconductor typically exhibits magnetoresistance oscillations whose
amplitude and temperature dependence are different from those stemming from the
Little-Parks effect. We demonstrate that these large resistance oscillations
(as well as the monotonic background on which they are superimposed) are due to
{\it current-excited moving vortices}, where the applied current in competition
with the oscillating Meissner currents imposes/removes the barriers for vortex
motion in increasing magnetic field. Due to the ever present current in
transport measurements, this effect should be considered in parallel with the
Little-Parks effect in low- samples, as well as with recently proposed
thermal activation of dissipative vortex-antivortex pairs in high-
samples
Dynamics of lane formation in driven binary complex plasmas
The dynamical onset of lane formation is studied in experiments with binary
complex plasmas under microgravity conditions. Small microparticles are driven
and penetrate into a cloud of big particles, revealing a strong tendency
towards lane formation. The observed time-resolved lane formation process is in
good agreement with computer simulations of a binary Yukawa model with Langevin
dynamics. The laning is quantified in terms of the anisotropic scaling index,
leading to a universal order parameter for driven systems.Comment: 4 pages, 3 figures, movies available at
http://www.mpe.mpg.de/pke/lane-formation
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