2,276 research outputs found
Mirrorless Negative-index Parametric Micro-oscillator
The feasibility and extraordinary properties of mirrorless parametric
oscillations in strongly absorbing negative-index metamaterials are shown. They
stem from the backwardness of electromagnetic waves inherent to this type of
metamaterials.Comment: 4 pages, 2 figure
Chlorine Adsorption on TiO2(110)/Water Interface: Nonadiabatic Molecular Dynamics Simulations for Photocatalytic Water Splitting
This study was financially supported M-ERA.NET project CatWatSplit. Institute of Solid State Physics, University of Latvia, as the Center of Excellence, has received funding from the European Union’s Horizon 2020 Framework Program H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under Grant Agreement No. 739508, project CAMART2. The calculations were performed at the Latvian SuperCluster (LASC) located in Institute of Solid State Physics, University of Latvia.Chloride is one of the most abundant ions in sea water, which is more available than fresh water. Due to lack of H2O adsorbate states near the valence band maximum (VBM) edge, the difficulty of water dissociation incidents has been reported on the rutile TiO2 surface as the excitation energy is around the band gap energy of TiO2. It is interesting whether the extra chloride can be a benefit to the water dissociation or not. In this study, the models of chlorine adatoms placed on the rutile TiO2 (110)/water interface are constructed using ab initio methods. The time-dependent spatial charges, bond-lengths of water molecules, and Hirshfeld charges are calculated by real-time time-dependent density functional theory and the Ehrenfest dynamics theory for investigating the excited state nonadiabatic dynamics of water dissociation. This study presents two photoinduced water-splitting pathways related to chlorine and analyzes the photogenerated hole along the reactions. The first step of water dissociation relies on the localized competition of oxygen charges between the dissociated water and the bridge site of TiO2 for transforming the water into hydroxyl and hydrogen by photoinduced driving force. --//-- This is an open access article Y.-P. Lin, D. Bocharov, I. Isakoviča, V. Pankratov, A.A. Popov, A.I. Popov, S. Piskunov; Chlorine adsorption on TiO2(110)/water interface: Nonadiabatic molecular dynamics simulations for potocatalytic water splitting; Electron. Mater., 2023, 4, pp. 33-48; DOI: 10.3390/electronicmat4010004; https://www.mdpi.com/2673-3978/4/1/4 published under the CC BY 4.0 licence.M-ERA.NET project CatWatSplit; Institute of Solid State Physics, University of Latvia, as the Center of Excellence, has received funding from the European Union’s Horizon 2020 Framework Program H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under Grant Agreement No. 739508, project CAMART2
Micromagnetic and Magnetoresistance Studies of Ferromagnetic La\u3csub\u3e0.83\u3c/sub\u3eSr\u3csub\u3e0.13\u3c/sub\u3eMnO\u3csub\u3e2.98\u3c/sub\u3e Crystals
Magnetic force microscopy (MFM) and atomic force microscopy (AFM) were used to investigate the surface topography and micromagnetic structure of La0.83Sr0.13MnO2.98 single crystals with colossal magnetoresistance (CMR). The crystals were grown by fused salt electrolysis and characterized by chemical analysis, X-ray diffraction, magnetic and transport measurements. The crystals are rhombohedral (R 3 c). Magnetic and transport measurements indicate that the ferromagnetic ordering at 310 K is associated with an insulator-metal transition at the same temperature. A maximum negative magnetoresistance (-62 %) is observed at 290 K in an applied magnetic field of 5 T. The magnetoresistance increases in magnitude sharply (1.8 %), comparing to the rest of the change, with increasing magnetic field up to 20 G, and then it increases slowly with increasing field.
MFM and AFM were used to study the (110) surface as well as a number of unspecified surfaces. Surface topography of an as-grown crystal exhibits well-developed surface corrugations due to extensive twinning. The corrugation angle at twin boundaries can be related to the unit cell parameters, surface and twinning planes. Magnetic force microscopy images show that magnetic domain boundaries are pinned to the crystallographic twins; a small number of unpinned boundaries are observed. The statistical analysis of domain boundary angle distribution is consistent with cubic magnetocrystalline anisotropy with easy axis along [100] directions for this material. Unusual magnetization behavior in the vicinity of topological defects on the surface is also reported. MFM contrast was found to disappear above the ferromagnetic Curie temperature; after cooling a new magnetic structure comprised of Bloch walls of opposite chiralities developed
Nonlinear coherent optical systems in the presence of equalization enhanced phase noise
Equalization enhanced phase noise (EEPN) occurs due to the interplay between laser phase noise and electronic dispersion compensation (EDC) module. It degrades significantly the performance of uncompensated long-haul coherent optical fiber communication systems. In this work, a general expression accounting for EEPN is presented based on Gaussian noise model to evaluate the performance of multi-channel optical communication systems using EDC and digital nonlinearity compensation (NLC). The nonlinear interaction between the signal and the EEPN is analyzed. Numerical simulations are carried out in nonlinear Nyquist-spaced wavelength division multiplexing (WDM) coherent transmission systems. Significant performance degradation due to EEPN in the cases of EDC and NLC are observed, with and without the consideration of transceiver (TRx) noise. The validation of the analytical approach has been done via split-step Fourier simulations. The maximum transmission distance and the laser linewidth tolerance are also estimated to provide important insights into the impact of EEPN
First results of the Kourovka Planet Search: discovery of transiting exoplanet candidates in the first three target fields
We present the first results of our search for transiting exoplanet
candidates as part of the Kourovka Planet Search (KPS) project. The primary
objective of the project is to search for new hot Jupiters which transit their
host stars, mainly in the Galactic plane, in the magnitude range of 11 to
14 mag. Our observations were performed with the telescope of the MASTER
robotic network, installed at the Kourovka astronomical observatory of the Ural
Federal University (Russia), and the Rowe-Ackermann Schmidt Astrograph,
installed at the private Acton Sky Portal Observatory (USA). As test
observations, we observed three celestial fields of size deg
during the period from 2012 to 2015. As a result, we discovered four transiting
exoplanet candidates among the 39000 stars of the input catalogue. In this
paper, we provide the description of the project and analyse additional
photometric, spectral, and speckle interferometric observations of the
discovered transiting exoplanet candidates. Three of the four transiting
exoplanet candidates are most likely astrophysical false positives, while the
nature of the fourth (most promising) candidate remains to be ascertained.
Also, we propose an alternative observing strategy that could increase the
project's exoplanet haul.Comment: 11 pages, 16 figures; Accepted for publication in Monthly Notices of
the Royal Astronomical Society 201
Sulfide mineralization, native gold and its geochemical connections in the Riphean deposits of the Avzyan ore-bearing region (the Southern Urals)
In the Avzyan ore-bearing region the sulfides from the low-sulfide gold-quartz deposits (Ulyuk-Bar, Kurgashly) are characterized by higher concentrations of As, Co, Ni, Cu, Pb in comparison with sulfides from sediments outside of ore-bearing zones. The gold is associated with As and sometimes - with S and Co. Gold-bearing sulfides are situated mostly in sandstones, where they were formed as a result of replacement of early formed ore-free pyrites by arsenopyrite and its association with arsenic pyrite during fluid movement ( Т = 250-450°С, Р = 26-360 bar) through fault zones. This process is fixed in the zonal distribution of arsenic pyrite and in varying behavior of total As in rocks. The proportion of p-type conduction pyrite increases with the depth, and zones of its development and high content of As in rocks are controlled by faults. The strong positive correlation of Au with S, Cu, Co, Pb, Ni, Zn is marked at the gold-sulfide (Bogryashka) and gold-sulfide-quartz (Gorny Priisk) occurrences. The connection of Au with As is not clear. At the Bogryashka occurrence pyrites are characterized by high concentrations of Sb, at the Vostochno-Aktashskoe occurrence - by Co and V. The gold in the Gorny Priisk ore deposit and in the Bogryashka occurrence is characterized by high ratio Au/Ag (>21) and impurity of Bi (0.4-1.2 wt %). The ratio Au/Ag is 5-8 in the gold from the Ulyuk-Bar and the Vostochno-Aktashskoe occurrences. Native gold in the Ulyuk-Bar and the Bogryashka occurences is associated with uranium-thorium minerals
The January 2015 outburst of a red nova in M31
M31N 2015-01a (or M31LRN 2015) is a red nova that erupted in January 2015 --
the first event of this kind observed in M31 since 1988. Very few similar
events have been confirmed as of 2015. Most of them are considered to be
products of stellar mergers. Results of an extensive optical monitoring of the
transient in the period January-March 2015 are presented. Eight optical
telescopes were used for imaging. Spectra were obtained on BTA, GTC and the
Rozhen 2m telescope. We present a highly accurate 70 d lightcurve and
astrometry with a 0.05" uncertainty. The color indices reached a minimum 2-3 d
before peak brightness and rapidly increased afterwards. The spectral type
changed from F5I to F0I in 6 d before the maximum and then to K3I in the next
30 d. The luminosity of the transient was estimated to
during the optical maximum. Both the
photometric and the spectroscopic results confirm that the object is a red
nova, similar to V838 Monocerotis.Comment: 5 pages, 4 figures, 4 tables, accepted for publication in Astronomy
and Astrophysics as a Letter to the Editor; page 5 is online material onl
Electron Beam-Assisted Synthesis of YAG:Ce Ceramics
The work was carried out within the framework of the grant AP14870696 of the Ministry of Education and Science of the Republic of Kazakhstan. This research was funded by the Russian Science Foundation of the Russian Federation. (Grant No. 23-73-00108). A.I.P is also thankful for financial support from Latvian Project LZP-2018/1-0214. In addition, A.I.P. is thanking the Institute of Solid State Physics, University of Latvia (ISSP UL). ISSP UL as the Centre of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD01-2016-2017-Teaming Phase2 under grant agreement No. 739508, project CAMART2.In this work, we present the results of the structure and luminescence properties of YAG:Ce (Y3Al5O12 doped with Ce3+ ions) ceramic samples. Their synthesis was carried out by sintering samples from the initial oxide powders under the powerful action of a high-energy electron beam with an energy of 1.4 MeV and a power density of 22–25 kW/cm2. The measured diffraction patterns of the synthesized ceramics are in good agreement with the standard for YAG. Luminescence characteristics at stationary/time-resolved regimes were studied. It is shown that under the influence of a high-power electron beam on a mixture of powders, it is possible to synthesize YAG:Ce luminescent ceramics with characteristics close to the well-known YAG:Ce phosphor ceramics obtained by traditional methods of solid-state synthesis. Thus, it has been demonstrated that the technology of radiation synthesis of luminescent ceramics is very promising. © 2023 by the authors. --//-- Karipbayev Z.T., Lisitsyn V.M., Golkovski M.G., Zhilgildinov Z.S., Popov A.I., Zhunusbekov A.M., Polisadova E., Tulegenova A., Mussakhanov D.A., Alpyssova G., Piskunov S.; Electron Beam-Assisted Synthesis of YAG:Ce Ceramics; (2023) Materials, 16 (11), art. no. 4102; DOI: 10.3390/ma16114102; https://www.scopus.com/inward/record.uri?eid=2-s2.0-85161490971&doi=10.3390%2fma16114102&partnerID=40&md5=e33da4c2d44c563881bdeffe410d734b published under the CC BY 4.0 licence.Grant AP14870696 of the Ministry of Education and Science of the Republic of Kazakhstan; Russian Science Foundation of the Russian Federation Grant No. 23-73-00108; the Latvian Council of Science LZP-2018/1-0214; ISSP UL as the Centre of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD01-2016-2017-Teaming Phase2 under grant agreement No. 739508, project CAMART2
Impact of Plasmonic Nanoparticles on Poikilocytosis and Microrheological Properties of Erythrocytes
Plasmonic nanoparticles (NP) possess great potential in photothermal therapy and diagnostics. However, novel NP require a detailed examination for potential toxicity and peculiarities of interaction with cells. Red blood cells (RBC) are important for NP distribution and the development of hybrid RBC-NP delivery systems. This research explored RBC alterations induced by noble (Au and Ag) and nitride-based (TiN and ZrN) laser-synthesized plasmonic NP. Optical tweezers and conventional microscopy modalities indicated the effects arising at non-hemolytic levels, such as RBC poikilocytosis, and alterations in RBC microrheological parameters, elasticity and intercellular interactions. Aggregation and deformability significantly decreased for echinocytes independently of NP type, while for intact RBC, all NP except Ag NP increased the interaction forces but had no effect on RBC deformability. RBC poikilocytosis promoted by NP at concentration 50 μg mL−1 was more pronounced for Au and Ag NP, compared to TiN and ZrN NP. Nitride-based NP demonstrated better biocompatibility towards RBC and higher photothermal efficiency than their noble metal counterparts
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