154 research outputs found
Vortex-antivortex wavefunction of a degenerate quantum gas
A mechanism of a pinning of the quantized matter wave vortices by optical
vortices in a specially arranged optical dipole traps is discussed. The
vortex-antivortex optical arrays of rectangular symmetry are shown to transfer
angular orbital momentum and form the "antiferromagnet"-like matter waves. The
separable Hamiltonian for matter waves in pancake trapping geometry is proposed
and 3D-wavefunction is factorized in a product of wavefunctions of the 1D
harmonic oscillator and 2D vortex-antivortex quantum state. The 2D
wavefunction's phase gradient field associated via Madelung transform with the
field of classical velocities forms labyrinth-like structure. The macroscopic
quantum state composed of periodically spaced counter-rotating BEC superfluid
vortices has zero angular momentum and nonzero rotational energy.Comment: 11 pages, 5 figure
Superfluid rotation sensor with helical laser trap
The macroscopic quantum states of the dilute bosonic ensemble in helical
laser trap at the temperatures about are considered in the
framework of the Gross-Pitaevskii equation. The helical interference pattern is
composed of the two counter propagating Laguerre-Gaussian optical vortices with
opposite orbital angular momenta and this pattern is driven in
rotation via angular Doppler effect. Macroscopic observables including linear
momentum and angular momentum of the atomic cloud are evaluated explicitly. It
is shown that rotation of reference frame is transformed into translational
motion of the twisted matter wave. The speed of translation equals the group
velocity of twisted wavetrain and alternates with a sign
of the frame angular velocity and helical pattern handedness .
We address detection of this effect using currently accessible laboratory
equipment with emphasis on the difference between quantum and classical fluids.Comment: 8 pages, 3 figures, accepted to publication Journ.Low Temp.Phy
Twisted speckle entities inside wavefront reversal mirrors
The previously unknown property of the optical speckle pattern reported. The
interference of a speckle with an oppositely moving phase-conjugated speckle
wave produces a randomly distributed ensemble of a twisted entities (ropes)
surrounding optical vortex lines. These entities appear in a wide range of
randomly chosen speckle parameters inside the phase-conjugating mirrors
regardless to an internal physical mechanism of the wavefront reversal. These
numerically generated interference patterns are relevant to a Brillouin -mirrors and to a four-wave mixing -mirrors based upon laser trapped
ultracold atomic cloud.Comment: 4 pages,3 figures, Accepted to Physical Review
Surface functionalization of biomedical Ti-6Al-7Nb alloy by liquid metal dealloying
Surface functionalization is an effective approach to change the surface properties of a material to achieve a specific goal such as improving the biocompatibility of the material. Here, the surface of the commercial biomedical Ti-6Al-7Nb alloy was functionalized through synthesizing of a porous surface layer by liquid metal dealloying (LMD). During LMD, the Ti-6Al-7Nb alloy is immersed in liquid magnesium (Mg) and both materials react with each other. Particularly, aluminum (Al) is selectively dissolved from the Ti-6Al-7Nb alloy into liquid Mg while titanium (Ti) and niobium (Nb) diffuse along the metal/liquid interface to form a porous structure. We demonstrate that the porous surface layer in the Ti-6Al-7Nb alloy can be successfully tailored by LMD. Furthermore, the concentration of harmful Al in this porous layer is reduced by about 48% (from 5.62 ± 0.11 wt.% to 2.95 ± 0.05 wt.%) after 30 min of dealloying at 1150 K. The properties of the porous layer (e.g., layer thickness) can be tuned by varying the dealloying conditions. In-vitro tests suggest improved bone formation on the functionalized porous surface of the Ti-6Al-7Nb alloy. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.European Research Council, ERCTohoku UniversityMinistry of Science and Higher Education of the Russian FederationNanjing University of Science and Technology, NUST: K2-2020-020MA 3333/13-1Supervision, I.V.O., R.W.-R., L.Z., L.M., J.E. and H.K.; Validation, I.V.O., S.-H.J., and B.L.; Writing – original draft, I.V.O. and B.L.; Writing – review & editing, all. All authors have read and agreed to the published version Funding: The financial support was provided by the German Science Foundation under the Leibniz Program of the manuscript. (Grant MA 3333/13-1), by the European Research Council (ERC) under the ERC Advanced Grant INTELHYB (grant Funding: The financial support was provided by the German Science Foundation under the Leibniz Program Ministry of Science and Higher Education of the Russian Federation, in the framework of the Increase Competitiveness (Grant MA 3333/13-1), by the European Research Council (ERC) under the ERC Advanced Grant INTELHYB Program of NUST «MISiS» (grant number K2-2020-020). I.V.O. is grateful for the financial support provided by the International Collaboration Center, Institute for Materials Research (ICC-IMR), Tohoku University, Japan. 02.A03.21.0006), and the Ministry of Science and Higher Education of the Russian Federation, in the framework Conflicts of Interest: The authors declare no conflict of interest. of the Increase Competitiveness Program of NUST «MISiS» (grant number K2-2020-020). I.V.O. is grateful for the financial support provided by the International Collaboration Center, Institute for Materials Research (ICC-IMR), Tohoku University, Japan
Experimental observation of spontaneous spin polarization of electrons in hybridized states of transition element impurities in semiconductors
Experimental evidence of the possible existence of spontaneous spin polarization of the electron system in hybridized states formed by transition element impurity atoms in the conduction band of semiconducting crystals is examined. The details of a quantitative interpretation of experiments on the temperature dependence of the specific heat and elastic moduli of mercury selenide crystals with iron impurities confirm the feasibility of establishing the presence of electron spin polarization in this type of experiment, as well as the possible existence of polarization in the crystals studied here. Theoretical arguments support the observation of a thermodynamic anomalous Hall effect owing to spontaneously polarized donor electrons from low-concentration impurities. © 2013 AIP Publishing LLC
ENDOR study of irradiated tooth enamel
γ- and x-irradiated tooth enamel has been studied by EPR and ENDOR. Radiation-induced EPR spectrum of tooth enamel was found to be a superposition of signals with dominant contribution determined by CO₂- radicals. Two types of these radicals were observed: ordered and disordered centers. EPR spectra of both CO₂- centers are described by axial g-tensor with g = 1.9975 and g ⊥= 2.0021 with g || c. The ENDOR spectrum of unannealed enamel powder consists of a singlet at Larmor frequency of ³¹P nuclei and doublet at Larmor frequency of ¹H nuclei. Samples annealing at T = 200-250 ⁰C resulted in the destruction of disordered centers and appearence of superhyperfine structure of ENDOR spectra. Its analysis with advanced the powder ENDOR theory allows to determine the superhyperfine constants and to find for the first time that the ordered CO₂- radical is located in B sites (phosphorous position) of bioapatite lattice. This substitution is accompanied by the shift of the nuclei of the first ³¹P shell towards the defects by 0.04 nm and the formation of the OH vacancy in the nearest radical surroundings
Open porous α + β titanium alloy by liquid metal dealloying for biomedical applications
Open porous dendrite-reinforced TiMo alloy was synthesized by liquid metal dealloying of the precursor Ti47.5Mo2.5Cu50 (at.%) alloy in liquid magnesium (Mg). The porous TiMo alloy consists of α-titanium and β-titanium phases and possesses a complex microstructure. The microstructure consists of micrometer scale β-titanium dendrites surrounded by submicrometer scale α-titanium ligaments. Due to the dendrite-reinforced microstructure, the porous TiMo alloy possesses relatively high yield strength value of up to 180 MPa combined with high deformability probed under compression loading. At the same time, the elastic modulus of the porous TiMo alloy (below 10 GPa) is in the range of that found for human bone. This mechanical behavior along with the open porous structure is attractive for biomedical applications and suggests opportunities for using the porous TiMo alloy in implant applications. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.Ilya V. Okulov is grateful for the financial support provided by the German Science Foundation under the Leibniz Program (grant MA 3333/13-1). We also want to acknowledge the fruitful discussion with Jürgen Markmann
Magnetization in AIIIBV semiconductor heterostructures with the depletion layer of manganese
The magnetic moment and magnetization in GaAs/GaInAs/GaAs
heterostructures with Mn deluted in GaAs cover layers and with atomically
controlled Mn -layer thicknesses near GaInAs-quantum well (3 nm)
in temperature range T=(1.8-300)K in magnetic field up to 50 kOe have been
investigated. The mass magnetization all of the samples of
GaAs/GaInAs/GaAs with Mn increases with the increasing of the
magnetic field that pointed out on the presence of low-dimensional
ferromagnetism in the manganese depletion layer of GaAs based structures. It
has been estimated the manganese content threshold at which the ferromagnetic
ordering was found.Comment: 8 pages, 3 figure
PIV study of the effect of piston position on the in-cylinder swirling flow during the scavenging process in large two-stroke marine diesel engines
A simplified model of a low speed large two-stroke marine diesel engine cylinder is developed. The effect of piston position on the in-cylinder swirling flow during the scavenging process is studied using the stereoscopic particle image velocimetry technique. The measurements are conducted at different cross-sectional planes along the cylinder length and at piston positions covering the air intake port by 0, 25, 50 and 75%. When the intake port is fully open, the tangential velocity profile is similar to a Burgers vortex, whereas the axial velocity has a wake-like profile. Due to internal wall friction, the swirl decays downstream, and the size of the vortex core increases. For increasing port closures, the tangential velocity profile changes from a Burgers vortex to a forced vortex, and the axial velocity changes correspondingly from a wake-like profile to a jet-like profile. For piston position with 75% intake port closure, the jet-like axial velocity profile at a cross-sectional plane close to the intake port changes back to a wake-like profile at the adjacent downstream cross-sectional plane. This is characteristic of a vortex breakdown. The non-dimensional velocity profiles show no significant variation with the variation in Reynolds numbe
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