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DDO68 is a star-forming (SF) dwarf galaxy residing in a nearby void. Its gas metallicity is among the lowest known in the local Universe, with parameter 12+log(O/H) in the range of 6.96-7.3 dex. Six of its SF regions are located in or near the so-called 'Northern Ring', in which the Hubble Space Telescope (HST) images reveal many luminous young stars. We present for these SF regions (Knots) the results of optical monitoring in 35 epochs during the years 2016--2023. The data was acquired with the 6m (BTA) and the 1m telescopes of the Special Astrophysical Observatory and the 2.5m telescope of the MSU Caucasian Mountain Observatory. We complement the above results with the archive data from 10 other telescopes for 11 epochs during the years 1988-2013 and with 3 our BTA observations between 2005 and 2015. Our goal is to search for variability of these Knots and to relate it to the probable light variations of their brightest stars. One of them, DDO68-V1 (in Knot 3), was identified in 2008 with a luminous blue variable (LBV) star, born in the lowest metallicity environments. For Knot 3, variations of its integrated light in the previous epochs reached ~0.8 mag. In the period since 2016, the amplitude of variations of Knot 3 reached ~0.3 mag. For the rest Knots, due to the lower amplitudes, the manifestation of variability is less pronounced. We examine the presence of variability via the criterion chi^{2} and the Robust Median Statistics and discuss the robustness of the detected variations. The variability is detected according to the both criteria in the lightcurves of all Knots with the chi^{2} confidence level of alpha = 0.0005. The peak-to-peak amplitudes of variations are ~0.09, ~0.13, ~0.11, ~0.08 and ~0.16 mag for Knots 1, 2, 4, 5 and 6, respectively. The amplitudes of the related variations of the brightest supergiants in these regions can reach of ~3.0 mag., Comment: 24 pages, 9 figures, accepted to Astrophysical Bulletin, vol. 79, No. 4 (2024)

Superconducting qubits are considered as a promising platform for implementing a fault tolerant quantum computing. However, surface defects of superconductors and the substrate leading to qubit state decoherence and fluctuations in qubit parameters constitute a significant problem. The amount and type of defects depend both on the chip materials and fabrication procedure. In this work, transmons produced by two different methods of aluminum etching: wet etching in a solution of weak acids and dry etching using a chlorine-based plasma are experimentally studied. The relaxation and coherence times for dry-etched qubits are more than twice as long as those for wet-etched ones. Additionally, the analysis of time fluctuations of qubit frequencies and relaxation times, which is an effective method to identify the dominant dielectric loss mechanisms, indicates a significantly lower impact of two-level systems in the dry-etched qubits compared to the wet-etched ones., Comment: 7 pages, 6 figures

Objective: To develop and evaluate a bore-integrated patch antenna array designed for whole-body excitation in ultra-high-field (UHF) magnetic resonance imaging (MRI) with improved transmit efficiency and address the limitations of existing RF coil designs. Methods: The proposed patch antenna array utilizes the MRI bore's RF shield as a functional component to enhance the RF magnetic field ($B_1^+$) distribution. Numerical simulations were conducted to compare the performance of the patch antenna array to bore-integrated stripline and local dipole arrays. A decoupling structure was implemented to minimize coupling between adjacent patch antennas. The performance of the patch array was evaluated experimentally. Results: The proposed patch array provides 3.9 times higher averaged transmit (Tx) efficiency in the CP mode and 3.0 times higher for the phase shimming regime versus the bore-integrated stripline array. Conclusion: Compared to the stripline array, the bore-integrated patch antenna array offers significant improvements in Tx efficiency for whole-body UHF MRI. Significance: The findings support the feasibility of integrating arrays into the RF shield of MRI scanners. This could broaden the clinical use of UHF body MRI technology., Comment: 9 pages, 7 figures, 1 table

We present CWRCzech, Click Web Ranking dataset for Czech, a 100M query-document Czech click dataset for relevance ranking with user behavior data collected from search engine logs of Seznam$.$cz. To the best of our knowledge, CWRCzech is the largest click dataset with raw text published so far. It provides document positions in the search results as well as information about user behavior: 27.6M clicked documents and 10.8M dwell times. In addition, we also publish a manually annotated Czech test for the relevance task, containing nearly 50k query-document pairs, each annotated by at least 2 annotators. Finally, we analyze how the user behavior data improve relevance ranking and show that models trained on data automatically harnessed at sufficient scale can surpass the performance of models trained on human annotated data. CWRCzech is published under an academic non-commercial license and is available to the research community at https://github.com/seznam/CWRCzech., Comment: Accepted to SIGIR 2024

The Orion Molecular Cloud complex, one of the nearest (D = 406 pc) and most extensively studied massive star-forming regions, is ideal for constraining the physics of stellar feedback, but its ~12 deg diameter on the sky requires a dedicated approach to mapping ionized gas structures within and around the nebula. The Sloan Digital Sky Survey (SDSS-V) Local Volume Mapper (LVM) is a new optical integral field unit (IFU) that will map the ionized gas within the Milky Way and Local Group galaxies, covering 4300 deg^2 of the sky with the new LVM Instrument. We showcase optical emission line maps from LVM covering 12 deg^2 inside of the Orion belt region, with 195,000 individual spectra combined to produce images at 0.07 pc (35.3") resolution. This is the largest IFU map made (to date) of the Milky Way, and contains well-known nebulae (the Horsehead Nebula, Flame Nebula, IC 434, and IC 432), as well as ionized interfaces with the neighboring dense Orion B molecular cloud. We resolve the ionization structure of each nebula, and map the increase in both the [SII]/Ha and [NII]/Ha line ratios at the outskirts of nebulae and along the ionization front with Orion B. [OIII] line emission is only spatially resolved within the center of the Flame Nebula and IC 434, and our ~0.1 pc scale line ratio diagrams show how variations in these diagnostics are lost as we move from the resolved to the integrated view of each nebula. We detect ionized gas emission associated with the dusty bow wave driven ahead of the star sigma Orionis, where the stellar wind interacts with the ambient interstellar medium. The Horsehead Nebula is seen as a dark occlusion of the bright surrounding photo-disassociation region. This small glimpse into Orion only hints at the rich science that will be enabled by the LVM., Comment: 13 pages, 10 figures, accepted for publication in A&A

Building a scalable universal high-performance quantum processor is a formidable challenge. In particular, the problem of realizing fast high-perfomance two-qubit gates of high-fidelity remains needful. Here we propose a unitary cell for a scalable quantum processor consisting of two transmons and a tunable three-mode coupler allowing for a ZZ interaction control. We experimentally demonstrate the native CZ gate with the pulse duration of 60~ns achieving the two-qubit gate fidelity above 98%, limited mostly by qubit coherence time. Numerical simulations show that by optimizing the gate duration the fidelity can be pushed over 99.97%., Comment: 13 pages, 9 figures, 3 tables

We present the Sloan Digital Sky Survey V (SDSS-V) Local Volume Mapper (LVM). The LVM is an integral-field spectroscopic survey of the Milky Way, Magellanic Clouds, and of a sample of local volume galaxies, connecting resolved pc-scale individual sources of feedback to kpc-scale ionized interstellar medium (ISM) properties. The 4-year survey covers the southern Milky Way disk at spatial resolutions of 0.05 to 1 pc, the Magellanic Clouds at 10 pc resolution, and nearby large galaxies at larger scales totaling $>4300$ square degrees of sky, and more than 55M spectra. It utilizes a new facility of alt-alt mounted siderostats feeding 16 cm refractive telescopes, lenslet-coupled fiber-optics, and spectrographs covering 3600-9800A at R ~ 4000. The ultra-wide field IFU has a diameter of 0.5 degrees with 1801 hexagonally packed fibers of 35.3 arcsec apertures. The siderostats allow for a completely stationary fiber system, avoiding instability of the line spread function seen in traditional fiber feeds. Scientifically, LVM resolves the regions where energy, momentum, and chemical elements are injected into the ISM at the scale of gas clouds, while simultaneously charting where energy is being dissipated (via cooling, shocks, turbulence, bulk flows, etc.) to global scales. This combined local and global view enables us to constrain physical processes regulating how stellar feedback operates and couples to galactic kinematics and disk-scale structures, such as the bar and spiral arms, as well as gas in- and out-flows., Comment: 29 pages, 12 figures, accepted for publication in The Astronomical Journal

We investigated the ionised and atomic gas kinematics and excitation state in the central region of ongoing star formation of the nearby low-metallicity dwarf galaxy Sextans B. The analysis is based on the new observations performed in Ha emission line with high resolution ($R \sim 16000$) scanning Fabry-Perot interferometer at the 6-m BTA SAO RAS telescope, and on the long-slit spectral observations at the 9.2-m SALT and 2.5-m CMO SAI MSU telescopes. Strong non-circular gas motions detected in the studied regions probably resulted from the off-plane gas motions and impact of stellar feedback. We identified six regions of elevated Ha velocity dispersion, five of which exhibit asymmetric or two-component Ha line profiles. Three of these regions are young ($<1.1$ Myr) expanding ($V_{\rm exp} \sim 25-50\ {\rm km\ s^{-1}}$) superbubbles. We argue that at least three regions in the galaxy could be supernova remnants. We conclude that supernovae feedback is the dominant source of energy for superbubbles in Sextans B, which is expected for such a low metallicity, although we cannot rule out a strong impact of pre-supernova feedback for one superbubble., Comment: 16 pages, 6+6 figures, 4 tables. submitted to MNRAS after revision

Search for the population of the low-energy continuum of tetraneutron system was performed for reactions of the $^{8}$He beam on deuterium target. These studies are performed for the data [I.A. Muzalevskii et al., Phys. Rev. C 103, 044313 (2021)], previously used for the studies of $^{7}$H and $^{6}$H in the $^2\text{H}(^8\text{He},{^3\text{He}})^{7}$H and $^2\text{H}(^8\text{He},{^4\text{He}})^{6}$H reactions. Evidence for a hump in the $^4n$ continuum at $3.5 \pm 0.7$ and $3.2 \pm 0.8$ MeV, was observed in the $^2$H($^8$He,$^6$Li)$^4$n and $^2$H($^8$He,$^3$He)$^7$H$\rightarrow ^3$H+$^4$n reactions, respectively. The observed statistics is quite low (6 and up to 40 events) corresponding to very low cross sections of few microbarns or tens of microbarns. The background conditions for the $^2$H($^8$He,$^6$Li)$^4n$ reaction are shown to be good, favoring the physical nature of the observed events. The $^2$H($^8$He,$^3$He)$^7$H$\rightarrow ^3$H+$^4n$ process transforms to the $^2$H($^8$He,$^6$Li$^{\ast})^4n$ reaction in the limit of the highest $^7$H decay energies. The population of the low-energy region in the $^{4}$n spectrum is found to be perfectly correlated with the population of the lowest $^{6}$Li states in the $^{3}$He+$^{3}$H continuum. Theoretical calculations of $^{8}$He in a five-body $\alpha$+$4n$ and of $^{4}$n in a four-body hyperspherical models are presented. The $^{8}$He wave function is shown to contain strong specific correlations, which may give rise to very low-energy structures in tetraneutron continuum in extreme-peripheral reaction scenarios., Comment: 13 pages, 9 figures

In the framework of the ongoing project, aimed at the systematical studying galaxies in nearby voids, we conducted spectroscopy with the Southern African Large Telescope (SALT) of 62 objects from the Nearby Void Galaxy (NVG) sample. They include 8 remaining objects of the 60 preselected candidates to eXtremely Metal-Poor (XMP) dwarfs, two known void XMP dwarfs and 52 void dwarfs residing within the Local Volume. For 47 galaxies residing in the nearby voids, we obtained spectra of the diverse quality. For 42 of them, we detected the Hydrogen and Oxygen lines that allowed us to get estimates of O/H in the observed HII regions. For 12 of the 42 objects, we detected the faint line [Oiii]4363, that allowed us to directly derive the electron temperature T_e and obtain their gas O/H by the direct method. 14 objects with the undetected [Oiii]4363 line fall to the lowest metallicities range (12+log(O/H) < 7.5 dex). For them, we use a carefully checked new empirical 'Strong line' method of Izotov et al. For 14 other objects with only strong lines detected and with 12+log(O/H) of ~7.5-8.0 dex, we used the modified version of 'semi-empirical' method of Izotov and Thuan. It accounts for effect of the excitation parameter O32 on T_e. 16 new galaxies are found with parameter 12+log(O/H) < 7.39 dex. Of them, four have 12+log(O/H) = 7.07 - 7.20 dex. Of the 60 observed NVG objects, 15 have mistaken radial velocities in HyperLEDA. They do not reside in the nearby voids., Comment: Accepted to MNRAS. 18 pages, 7 figures, 4 tables. Plus a separate file with the supplementary on-line material which includes finding charts, plots of 1d spectra and tables with emission-line fluxes and derived physical parameters and O/H

We present and discuss the results of the Giant Metrewave Radio Telescope (GMRT) HI 21-cm line mapping for five isolated low-mass (M_bary ~(2--8)*10^7 Mo) eXtremely Metal Poor (XMP) dwarfs [12+log(O/H)=7.13-7.28], selected from the Nearby Void Galaxy (NVG) sample. All the studied void dwarfs show the disturbed morphology in the HI maps with the angular resolutions of ~11" to ~40". We examine the HI morphology and velocity field and the relative orientation of their stellar and gas body spins. We discuss the overall non-equilibrium state of their gas and the possible origin and evolution of the studied void dwarfs. The most straightforward interpretation of the ubiquitous phenomenon of the gas component non-equilibrium state in these and similar void dwarfs is the cold accretion from the void filaments and/or minor mergers. The cold gas accretion in voids could be linked to the presence of small filaments that constitute the substructure of voids., Comment: 20 pages, 8 Figures, Accepted for publication in MNRAS

Scalable quantum computers hold the promise to solve hard computational problems, such as prime factorization, combinatorial optimization, simulation of many-body physics, and quantum chemistry. While being key to understanding many real-world phenomena, simulation of non-conservative quantum dynamics presents a challenge for unitary quantum computation. In this work, we focus on simulating non-unitary parity-time symmetric systems, which exhibit a distinctive symmetry-breaking phase transition as well as other unique features that have no counterpart in closed systems. We show that a qutrit, a three-level quantum system, is capable of realizing this non-equilibrium phase transition. By using two physical platforms -- an array of trapped ions and a superconducting transmon -- and by controlling their three energy levels in a digital manner, we experimentally simulate the parity-time symmetry-breaking phase transition. Our results indicate the potential advantage of multi-level (qudit) processors in simulating physical effects, where additional accessible levels can play the role of a controlled environment., Comment: 20 pages, 10 figures