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A new method for precise optical measurements of the sub-micron height of levitation of droplet clusters

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Particuology 2024年第4期87卷 173-178页

作者： Alexander A.Fedorets eduard e.Kolmakov leonid A.Dombrovsky University of Tyumen 6 Volodarskogo StTyumen625003Russia engineering Faculty Ariel UniversityP0.B.3407000ArielIsrael Joint Institute for High Temperatures 17A Krasnokazarmennaya StMoscow111116Russia

Droplet clusters levitating over the locally heated water surface are considered a very promising phe-nomenon of microfluidics for the potential use of the droplets as unique microreactors for microbio-logical experiments.A new optical method is suggested for precise measurements of the sub-micron levitation height of single *** method is based on the analysis of variable colors of the inter-ference halo around the *** the first time,it is possible to measure the extremely low downward velocity of droplets,which grow due to steam *** velocity was found to be 5-8 nm/*** height of the levitation of various droplets just before their coalescence with a layer of water was also *** measurements might be used for the verification of sophisticated models for the droplet levitation to be developed for a very thin layer of humid air under the droplet when the Knudsen effect should be taken into account.

关键词： Precise measurements Interferometric method Droplet cluster Levitation height

Quantum Supercurrent Transistors in Silicon Quantum Wells Confined by Superconductor Barriers

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Journal of Modern Physics 2011年第4期2卷 256-273页

作者： Nikolay T. Bagraev edward Yu. Danilovsky leonid e. klyachkin Andrei A. Kudryavtsev Roman V. Kuzmin Anna M. Malyarenko Wolfgang Gehlhoff Vladimir V. Romanov 不详

We present the findings of spin-dependent single-hole and pair-hole transport in plane and across the p-type high mobility silicon quantum wells (Si-QW), 2 nm, confined by the superconductor δ-barriers on the n-type Si (100) surface. The oscillations of the conductance in normal state and the zero-resistance supercurrent in superconductor state as a function of the top gate voltage are found to be correlated by on- and off-resonance tuning the two-dimensional levels of holes in Si-QW with the Fermi energy in the superconductor δ-barriers. The SIMS and STM studies have shown that the δ-barriers heavily doped with boron, 5 × 1021 cm–3, represent really alternating arrays of silicon empty and doped dots, with dimensions restricted to 2 nm. This concentration of boron seems to indicate that each doped dot located between empty dots contains two impurity atoms of boron. The ePR studies show that these boron pairs are the trigonal dipole centres, B+ - B–, that contain the pairs of holes, which result from the negative -U reconstruction of the shallow boron acceptors, 2B0 => B+ - B–. The electrical resistivity, magnetic susceptibility and specific heat measurements demonstrate that the high density of holes in the Si-QW (> 1011 cm–2) gives rise to the high temperature superconductor properties for the δ-barriers. The value of the superconductor energy gap obtained is in a good agreement with the data derived from the oscillations of the conductance in normal state and of the zero-resistance supercurrent in superconductor state as a function of the bias voltage. These oscillations appear to be correlated by on- and off-resonance tuning the two-dimensional subbands of holes with the Fermi energy in the superconductor δ-barriers. Finally, the proximity effect in the S-Si-QW-S structure is revealed by the findings of the quantization of the supercurrent and the multiple Andreev reflection (MAR) observed both across and along the Si-QW plane thereby identifying the spin transis

关键词： Silicon Quantum Well Superconductor δ-barrier eSR Dipole Boron Center Multiple Andreev Reflection Supercurrent Conductance eDeSR Silicon Microcavity

eDeSR and ODMR of Impurity Centers in Nanostructures Inserted in Silicon Microcavities

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Journal of Modern Physics 2011年第6期2卷 544-558页

作者： Nikolay T Bagraev Vladimir A. Mashkov edward Yu Danilovsky Wolfgang Gehlhoff Dmitrii S. Gets leonid e klyachkin Andrei A Kudryavtsev Roman V. Kuzmin Anna M Malyarenko Vladimir V Romanov 不详

We present the first findings of the new electrically- and optically-detected magnetic resonance technique [eD electron spin resonance (eDeSR) and (ODMR)] which reveal single point defects in the ultra-narrow silicon quantum wells (Si-QW) confined by the superconductor δ-barriers. This technique allows the eSR identification without the application of the external cavity as well as a high frequency source and recorder, with measuring the only magnetoresistance (eDeSR) and transmission (ODMR) spectra within frameworks of the excitonic normal-mode coupling (NMC) caused by the microcavities embedded in the Si-QW plane. The new resonant positive magnetoresistance data are interpreted here in terms of the interference transition in the diffusive transport of free holes respectively between the weak antilocalization regime in the region far from the eSR of a paramagnetic point defect located inside or near the conductive channel and the weak localization regime in the nearest region of the eSR of that defect.

关键词： Silicon Microcavity Quantum Well eSR Bound exciton Trigonal Centers Single Centers Carbon ODMR

Pulsed THz radiation under ultrafast optical discharge of vacuum photodiode

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Frontiers of Optoelectronics 2024年第2期 100-113页

作者： Aleksandr A.Ushakov Kseniia A.Mamaeva leonid V.Seleznev Georgy e.Rizaev Vladimir Bukin Timophey V.Dolmatov Pavel A.Chizhov Vladimir Bagdasarov Sergey V.Garnov Prokhorov General Physics Institute of the Russian Academy of Sciences Physical Institute Russian Academy of Sciences Moscow Institute of Physics and Technology Russian Institute for Scientific and Technical Information

In this paper, we first present an experimental demonstration of terahertz radiation pulse generation with energy up to 5 pJ under the electron emission during ultrafast optical discharge of a vacuum photodiode. We use a femtosecond optical excitation of metallic copper photocathode for the generation of ultrashort electron bunch and up to 45 kV/cm external electric field for the photo-emitted electron acceleration. Measurements of terahertz pulses energy as a function of emitted charge density, incidence angle of optical radiation and applied electric field have been provided. Spectral and polarization characteristics of generated terahertz pulses have also been studied. The proposed semi-analytical model and simulations in COMSOL Multiphysics prove the experimental data and allow for the optimization of experimental conditions aimed at flexible control of radiation parameters.

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Quantum Supercurrent Transistors in Silicon Quantum Wells Confined by Superconductor Barriers

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eDeSR and ODMR of Impurity Centers in Nanostructures Inserted in Silicon Microcavities

Journal of Modern Physics（现代物理） 2011年第4期

作者： Nikolay T. Bagraev edward Yu. Danilovsky leonid e. klyachkin Andrei A. Kudryavtsev Roman V. Kuzmin Anna M. Malyarenko Wolfgang Gehlhoff Vladimir V. Romanov

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Mechanisms Modeling the Double Rotation of the elytra in Beetles （Coleoptera）

Journal of Modern Physics（现代物理） 2011年第6期

作者： Nikolay T Bagraev Vladimir A. Mashkov edward Yu Danilovsky Wolfgang Gehlhoff Dmitrii S. Gets leonid e klyachkin Andrei A Kudryavtsev Roman V. Kuzmin Anna M Malyarenko Vladimir V Romanov

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Journal of Bionic engineering 2011年第4期8卷 395-405页

作者： leonid Frantsevich Schmalhausen-Institute of Zoology B. Chmielnicki str. 15 Kiev-3 O 01601 Ukraine

We recorded transient movements, i.e. opening and closing, of beetle elytra. The beetles were tethered from below and filmed under a skew mirror; two markers were glued on each elytron at the apex and at the base. Body-fixed 3D traces of the apical and basal markers were reconstructed. The trace of the basal marker was, as a rule, non-parallel to the apical trace. The costal edge of the elytron uniformly supinated in the course of adduction of the apical marker. We found two essential attributes of double rotation：（1） the elytron to body articulation is approximately a spherical mechanism; （2） transient opening and closing possess single degree of freedom. The double rotation was modeled with two mechanisms：（1） a flexagon model of the Haas and Wootton＇s type simulated the elytral movement relative to the movement of one facet of the flexagon; （2） a screw and nut model provided traces as two sectors of a helical thread, one sector was phase shifted with respect to other one. Screw guideways in a spherical mechanism give rise to discrepancies. exact solution for a spherical mechanism with two guideways was proposed. The modeling revealed the attribute （3）： the elytron is actuated by two linked but differently directed drives. experimental investigations on the elytron to body articulation may be oriented at search of those mechanisms.

关键词： insect flight insect thorax flexagon screw and nut joint

Shock standards Cu, Ag, Ir, and Pt in a wide pressure range

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Matter and Radiation at extremes 2023年第4期8卷 37-46页

作者： leonid Burakovsky Dean L.Preston Scott D.Ramsey Charles e.Starrett Roy S.Baty Los Alamos National Laboratory Los AlamosNew Mexico 87545USA

Although they are polymorphic(multiphase)materials,both copper and silver are reliable Hugoniot standards,and thus it is necessary to establish an accurate analytic model of their principal *** we present analytic forms of their principal Hugoniots,as well as those of iridium and platinum,two“pusher”standards for shock-ramp experiments,over a wide range of *** are based on our new analytic model of the principal Hugoniot[Burakovsky et al.,***.132,215109(2022)].Comparison of the four Hugoniots with experimental and independent theoretical data(such data exist to very high pressures for both copper and silver)demonstrates excellent ***,the new model for copper and silver can be considered as providing the corresponding Hugoniot standards over a wide pressure *** also suggest an approach for calculating the Grüneisen parameter along the Hugoniot and apply it to copper as a prototype,and our results appear to be in good agreement with the available data.

关键词： silver copper analytic

Subcritical dynamo and hysteresis in a Babcock-Leighton type kinematic dynamo model

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Research in Astronomy and Astrophysics 2021年第10期21卷 250-256页

作者： Vindya Vashishth Bidya Binay Karak leonid Kitchatinov Department of Physics Indian Institute of Technology(BHU)Varanasi 221005India Institute of Solar-Terrestrial Physics SB RAS Lermontov Str.126A664033IrkutskRussia Pulkovo Astronomical Observatory Pulkovskoe Sh.65St.Petersberg196140Russia

In the Sun and Sun-like stars,it is believed that cycles of the large-scale magnetic field are produced due to the existence of differential rotation and helicity in the plasma flows in their convection zones(CZs).Hence,it is expected that for each star,there is a critical dynamo number for the operation of a large-scale *** a star slows down,it is expected that the large-scale dynamo ceases to operate above a critical rotation *** our study,we explore the possibility of the operation of the dynamo in the subcritical region using the Babcock–Leighton type kinematic dynamo *** some parameter regimes,we find that the dynamo shows hysteresis behavior,i.e.,two dynamo solutions are possible depending on the initial parameters—decaying solution if starting with weak field and strong oscillatory solution(subcritical dynamo)when starting with a strong ***,under large fluctuations in the dynamo parameter,the subcritical dynamo mode is unstable in some parameter ***,our study supports the possible existence of subcritical dynamo in some stars which was previously demonstrated in a mean-field dynamo model with distributedαand MHD turbulent dynamo simulations.

关键词： magnetic field Sun:activity Sun:magnetic fields stars:rotation stars:dynamo stars