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533 results on '"Yakovlev, I. P."'

9. Experimental Study of Terahertz Radiation Generation in the Interaction of Ultrashort Laser Pulse with Gas Targets

Author

Zemskov, R. S., Perevalov, S. E., Kotov, A. V., Bodrov, S. B., Stepanov, A. N., Solov’ev, A. A., Bakunov, M. I., Luchinin, A. G., Ginzburg, V. N., Kuz’min, A. A., Yakovlev, I. V., Stukachev, S. E., Kochetkov, A. A., Shaikin, I. A., Shaykin, A. A., Khazanov, E. A., Glyavin, M. Yu., Chekmarev, N. V., Vodop’yanov, A. V., and Starodubtsev, M. V.

Published
2023
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11. Inferring possible magnetic field strength of accreting inflows in EXor-type objects from scaled laboratory experiments

Author

Burdonov, K., Bonito, R., Giannini, T., Aidakina, N., Argiroffi, C., Beard, J., Chen, S. N., Ciardi, A., Ginzburg, V., Gubskiy, K., Gundorin, V., Gushchin, M., Kochetkov, A., Korobkov, S., Kuzmin, A., Kuznetsov, A., Pikuz, S., Revet, G., Ryazantsev, S., Shaykin, A., Shaykin, I., Soloviev, A., Starodubtsev, M., Strikovskiy, A., Yao, W., Yakovlev, I., Zemskov, R., Zudin, I., Khazanov, E., Orlando, S., and Fuchs, J.

Subjects
Astrophysics - Solar and Stellar Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract

Aims. EXor-type objects are protostars that display powerful UV-optical outbursts caused by intermittent and powerful events of magnetospheric accretion. These objects are not yet well investigated and are quite difficult to characterize. Several parameters, such as plasma stream velocities, characteristic densities, and temperatures, can be retrieved from present observations. As of yet, however, there is no information about the magnetic field values and the exact underlying accretion scenario is also under discussion. Methods. We use laboratory plasmas, created by a high power laser impacting a solid target or by a plasma gun injector, and make these plasmas propagate perpendicularly to a strong external magnetic field. The propagating plasmas are found to be well scaled to the presently inferred parameters of EXor-type accretion event, thus allowing us to study the behaviour of such episodic accretion processes in scaled conditions. Results. We propose a scenario of additional matter accretion in the equatorial plane, which claims to explain the increased accretion rates of the EXor objects, supported by the experimental demonstration of effective plasma propagation across the magnetic field. In particular, our laboratory investigation allows us to determine that the field strength in the accretion stream of EXor objects, in a position intermediate between the truncation radius and the stellar surface, should be of the order of 100 gauss. This, in turn, suggests a field strength of a few kilogausses on the stellar surface, which is similar to values inferred from observations of classical T Tauri stars.

Published
2021
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19. Photon echo from localized excitons in semiconductor nanostructures

Author

Poltavtsev, S. V., Yugova, I. A., Yakovlev, I. A. Akimov D. R., and Bayer, M.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

An overview on photon echo spectroscopy under resonant excitation of the exciton complexes in semiconductor nanostructures is presented. The use of four-wave-mixing technique with the pulsed excitation and heterodyne detection allowed us to measure the coherent response of the system with the picosecond time resolution. It is shown that, for resonant selective pulsed excitation of the localized exciton complexes, the coherent signal is represented by the photon echoes due to the inhomogeneous broadening of the optical transitions. In case of resonant excitation of the trions or donor-bound excitons, the Zeeman splitting of the resident electron ground state levels under the applied transverse magnetic field results in quantum beats of photon echo amplitude at the Larmor precession frequency. Application of magnetic field makes it possible to transfer coherently the optical excitation into the spin ensemble of the resident electrons and to observe a long-lived photon echo signal. The described technique can be used as a high-resolution spectroscopy of the energy splittings in the ground state of the system. Next, we consider the Rabi oscillations and their damping under excitation with intensive optical pulses for the excitons complexes with a different degree of localization. It is shown that damping of the echo signal with increase of the excitation pulse intensity is strongly manifested for excitons, while on trions and donor-bound excitons this effect is substantially weaker.

Published
2018
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37. Systematic variations of interstellar linear polarization and growth of dust grains

Author

Voshchinnikov, N. V., Das, H. K., Yakovlev, I. S., and Il'in, V. B.

Subjects
Astrophysics - Astrophysics of Galaxies
Abstract

A quantitative interpretation of the observed relation between the interstellar linear polarization curve parameters $K$ and $\lambda_{\max}$ characterizing the width and the wavelength of a polarization maximum, respectively, is given. The observational data available for 57 stars located in the dark clouds in Taurus, Chamaeleon, around the stars $\rho$ Oph and R CrA are considered. The spheroidal particle model of interstellar dust grains earlier applied to simultaneously interpret the interstellar extinction and polarization curves in a wide spectral range is utilized. The observed trend $K \approx 1.7 \lambda_{\max}$ is shown to be most likely related to a growth of dust grains due to coagulation rather than mantle accretion. The relation of the parameters $K$ and $\lambda_{\max}$ with an average size of silicate dust grains is discussed., Comment: 16 pages, 8 figures, accepted for publication in Astronomy Letters

Published
2013
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44. Analogues of poly(l -phosphoserine) via living polymerization of phosphonate-containing N -carboxyanhydride monomers

Author

Yakovlev, I and Deming, TJ

Subjects
Macromolecular and Materials Chemistry, Resources Engineering and Extractive Metallurgy, Physical Chemistry, Physical Chemistry (incl. Structural)
Abstract

We have synthesized new phosphonate-containing-amino acid N-carboxyanhydride (NCA) monomers and used these to prepare well-defined phosphonate-containing polypeptides and block copolypeptides. These NCAs were found to undergo living polymerization to high molecular weights with narrow chain length distributions. The methods described here demonstrate that phosphono polypeptides are also readily incorporated into block copolymers with controlled architecture and composition. One polymer, poly(l- phosphonohomoalanine) (poly(Pha)), is an isosteric analogue of poly(l-phosphoserine) and was found to display a pH-responsive conformational change. The pH-responsive -helical conformation of poly(Pha) is unprecedented and may prove to be useful in the preparation of stimuli-responsive block copolypeptides containing poly(Pha) segments. © 2014 American Chemical Society.

Published
2014

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