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Robotic manipulation of fresh fruits and vegetables, including the grasping of multiple loose items, has a strong industrial need but it still is a challenging task for robotic manipulation. This paper outlines the distinctive manipulation strategies used by humans to pick loose fruits and vegetables with the aim to better adopt them for robotic manipulation of diverse items. In this work we present a first version of a robotic setup designed to pick different single or multiple fresh items, featuring multi-fingered compliant robotic gripper. We analyse human grasping strategies from the perspective of industrial Key Performance Indicators (KPIs) used in the logistic sector. The robotic system was validated using the same KPIs, as well as taking into account human performance and strategies. This paper lays the foundation for future development of the robotic demonstrator for fresh fruit and vegetable intelligent manipulation, and outlines the need for generic approaches to handle the complexity of the task., Comment: *Authors contributed equally

During the last decade and a half, the new generation spectropolarimeter Narval at Pic du Midi, France allowed the study of weak magnetic fields in cool giant stars that are fairly evolved after main sequence. We present a short summary on the recent knowledge on the magnetic fields and activity in giants situated in the upper right part of the Hertzsprung-Russel (H-R) diagram and discuss on the possible mechanisms for magnetic field generation in the asymptotic giants branch (AGB) and post-AGB stars., Comment: Accepted for publication in Bulgarian Astronomical Journal, volume 42 (2025)

We present high resolution (0.06 A/px) spectroscopic observations of the recurrent nova T Coronae Borealis obtained during the last 1.5 years (September 2022 -- January 2024), with the 2.0m RCC telecope of the Rozhen National Astronomical Observatory, Bulgaria. Double-peaked emission is visible in the H-alpha line after the end of the superactive state. We subtract the red giant contribution and measure the distance between the peaks ($\Delta v_a$) of the line. For the period July 2023 -- January 2024, we find that $\Delta v_a$ is in range $90 < \Delta v_a < 120$ km/s. Assuming that the emission is from the accretion disc around the white dwarf, we find average radius of the accretion disc $R_{disc} = 89 \pm 19$ R$_\odot$, which is approximately equal to the Roche lobe size of the white dwarf. Our results indicate that tidal torque plays an important role but that the disc can extend up to the Roche lobe of the accreting star., Comment: Astronomische Nachrichten (accepted)

We present a detailed long-term study of the single M6 III giant RZ~Ari to obtain direct and simultaneous measurements of the magnetic field, activity indicators, and radial velocity in order to infer the origin of its activity. We study its magnetic activity in the context of stellar evolution, and for this purpose, we also refined its evolutionary status and Li abundance. In general, for the M giants, little is known about the properties of the magnetic activity and its causes. RZ~Ari posses the strongest surface magnetic field of the known Zeeman-detected M giants and is bright enough to allow a deep study of its surface magnetic structure. The results are expected to shed light on the activity mechanism in these stars.

In this note we answer positively a question of Chris Godsil and Karen Meagher on the existence of a 2-design whose block graph has a non-canonical maximum clique without a design structure.

Dielectric losses are one of the key factors limiting the coherence of superconducting qubits. The impact of materials and fabrication steps on dielectric losses can be evaluated using coplanar waveguide (CPW) microwave resonators. Here, we report on superconducting CPW microwave resonators with internal quality factors systematically exceeding 5x106 at high powers and 2x106 (with the best value of 4.4x106) at low power. Such performance is demonstrated for 100-nm-thick aluminum resonators with 7-10.5 um center trace on high-resistivity silicon substrates commonly used in quantum Josephson junction circuits. We investigate internal quality factors of the resonators with both dry and wet aluminum etching, as well as deep and isotropic reactive ion etching of silicon substrate. Josephson junction compatible CPW resonators fabrication process with both airbridges and silicon substrate etching is proposed. Finally, we demonstrate the effect of airbridges positions and extra process steps on the overall dielectric losses. The best quality fa ctors are obtained for the wet etched aluminum resonators and isotropically removed substrate with the proposed ultrasonic metal edge microcutting., Comment: 6 pages, 2 figures

Transposition graph $T_n$ is defined as a Cayley graph over the symmetric group generated by all transpositions. It is known that all eigenvalues of $T_n$ are integers. Moreover, zero is its eigenvalue for any $n\geqslant 4$. But the exact distribution of the spectrum of the graph $T_n$ is unknown. In this paper we prove that integers from the interval $[-\frac{n-4}{2}, \frac{n-4}{2}]$ lie in the spectrum of $T_n$ if $n \geqslant 19$., Comment: 11 pages. arXiv admin note: text overlap with arXiv:2204.03153

We present the surface magnetic field conditions of the brightest pulsating RV Tauri star, R Sct. Our investigation is based on the longest spectropolarimetric survey ever performed on this variable star. The analysis of high resolution spectra and circular polarization data give sharp information on the dynamics of the atmosphere and the surface magnetism, respectively. Our analysis shows that surface magnetic field can be detected at different phases along a pulsating cycle, and that it may be related to the presence of a radiative shock wave periodically emerging out of the photosphere and propagating throughout the stellar atmosphere., Comment: 16 pages, 14 figures

Study of the local optical properties using electron beam (e-beam) can provide a valuable information concerning the inspection of the materials quality, the presence of the different phase inclusions and defects. Halide perovskites have been shown to be highly sensitive to external stress conditions like ambient atmosphere, light, and heat. In this paper, the cathodoluminescence (CL) spectroscopy has been exploited to carry out the investigation of CH3NH3PbBr3 monocrystals under low energy electron beam irradiation. The CL spectra exhibited strong transformation with the increase of the irradiation dose and significant shifts of the peak maximums from 2.23 eV to >2.5 eV. Utilizing a larger e-beam energy (>20 keV) was found to be preferable to slow down the dynamics of the decomposition and corrosion. The mechanisms of the changes in MAPbBr3 properties after e-beam exposure and correlation to the in-depth distribution of deposited energy were discussed., Comment: 8 pages, 3 figures

The defect-activity in halide perovskites remains a critical factor for the application in optoelectronics. The imperfections (vacancies, anti-sites, interstitials) formed in the lattice of the halide perovskites were considered as a main origin for the corrosion of the interfaces and decomposition process under external stress. At the same time, the self-healing effect was reported as one of the features for the devices based on halide perovskites, which manifests in the recovery of device performance under specific conditions. Such processes require a detailed analysis for the quantitative analysis of the defect parameters. In this work, we used Admittance and Optical Deep-level Transient spectroscopy to determine the evolution of the defect energy levels in the simplified rectifying device architecture based on CH3NH3PbBr3 after consecutive accumulation of the absorbed radiation dose (fast electrons, 5 MeV). We found that electron beam irradiation induces the formation of the deep states of anti-sites PbBr with activation energy of 0.83 eV. Increase of the absorbed radiation dose up to 1.5 Mrad resulted in a critical raise of 0.83 eV defect concentration, which can be effectively annealed during the temperature sweep. The changes in the defect parameters after different values of the absorbed radiation dose were analyzed and discussed. The current work provides new insights for the self-healing process of halide perovskite-based devices under hard external stress, revealing the important specifics of the defect behavior., Comment: Upgrade of results

The connected coalition in a graph $G=(V,E)$ consists of two disjoint sets of vertices $V_{1}$ and $V_{2}$, neither of which is a connected dominating set but whose union $V_{1}\cup V_{2}$, is a connected dominating set. A connected coalition partition in a graph $G$ of order $n=|V|$ is a vertex partition $\psi$ = $\{V_1, V_2,..., V_k \}$ such that every set $V_i \in \psi$ either is a connected dominating set consisting of a single vertex of degree $n-1$, or is not a connected dominating set but forms a connected coalition with another set $V_j\in \psi$ which is not a connected dominating set. The connected coalition number, denoted by $CC(G)$, is the maximum cardinality of a connected coalition partition of $G$. In this paper, we initiate the study of connected coalition in graphs and present some basic results. Precisely, we characterize all graphs that have a connected coalition partition. Moreover, we show that for any graph $G$ of order $n$ with $\delta(G)=1$ and with no full vertex, it holds that $CC(G)

Lab-on-a-chip (LOC) forms the basis of the new-generation portable analytical systems. LOC allows the manipulation of ultralow flows of liquid reagents and multistep reactions on a microfluidic chip, which requires a robust and precise instrument to control the flow of liquids on a chip. However, commercially available flow meters appear to be a standalone option adding a significant dead volume of tubes for connection to the chip. Furthermore, most of them cannot be fabricated within the same technological cycle as microfluidic channels. Here, we report on a membrane-free microfluidic thermal flow sensor (MTFS) that can be integrated into a silicon-glass microfluidic chip with a microchannel topology. We propose a membrane-free design with thin-film thermo-resistive sensitive elements isolated from microfluidic channels and 100 mm wafers silicon-glass fabrication route. It ensures MTFS compatibility with corrosive liquids, which is critically important for biological applications. MTFS design rules for the best sensitivity and measurement range are proposed. A method for automated thermo-resistive sensitive elements calibration is described. The device parameters are experimentally tested for hundreds of hours with a reference Coriolis flow sensor demonstrating a relative flow error of less than 5% within the range of 2-30 uL/min along with a sub-second time response.

The coalition in a graph $G$ consists of two disjoint sets of vertices $V_{1}$ and $V_{2}$, neither of which is a dominating set but whose union $V_{1}\cup V_{2}$, is a dominating set. A coalition partition in a graph $G$ is a vertex partition $\pi$ = $\{V_1, V_2,..., V_k \}$ such that every set $V_i \in \pi$ is not a dominating set but forms a coalition with another set $V_j\in \pi$ which is not a dominating set. The coalition number $C(G)$ equals the maximum $k$ of a coalition partition of $G$. In this paper, we compute the coalition number of all cubic graphs of order at most $10$., Comment: 14 pages, 3 figures

Fused silica glass is a material of choice for micromechanical, microfluidic, and optical devices due to its ultimate chemical resistance, optical, electrical, and mechanical performance. Wet etching in hydrofluoric solutions especially a buffered oxide etching (BOE) solution is still the key method for fabricating fused silica glass-based microdevices. It is well known that protective mask integrity during deep fused silica wet etching is a big challenge due to chemical stability of fused glass and extremely aggressive BOE properties. Here, we propose a multilevel fused silica glass microstructures fabrication route based on deep wet etching through a stepped mask with just a one grayscale photolithography step. First, we provide a deep comprehensive analysis of a fused quartz dissolution mechanism in BOE solution and calculate the main fluoride fractions like $HF^-_2$, $F^-$, $(HF)_2$ components in a BOE solution as a function of pH and $NH_4F:HF$ ratio at room temperature. Then, we experimentally investigate the influence of BOE concentration ($NH_4F:HF$ from 1:1 to 14:1) on the mask resistance, etch rate and profile isotropy during fused silica 60 minutes etching through a metal/photoresist mask. Finally, we demonstrate a high-quality multilevel over-200 um isotropic wet etching process with the rate up to 3 um/min, which could be of a great interest for advanced fused silica microdevices with flexure suspensions, inertial masses, microchannels, and through-wafer holes., Comment: 11 pages, 6 figures

V. Levenshtein first proposed the sequence reconstruction problem in 2001. This problem studies the model where the same sequence from some set is transmitted over multiple channels, and the decoder receives the different outputs. Assume that the transmitted sequence is at distance $d$ from some code and there are at most $r$ errors in every channel. Then the sequence reconstruction problem is to find the minimum number of channels required to recover exactly the transmitted sequence that has to be greater than the maximum intersection between two metric balls of radius $r$, where the distance between their centers is at least $d$. In this paper, we study the sequence reconstruction problem of permutations under the Hamming distance. In this model we define a Cayley graph over the symmetric group, study its properties and find the exact value of the largest intersection of its two metric balls for $d=2r$. Moreover, we give a lower bound on the largest intersection of two metric balls for $d=2r-1$.

During the last years, giant optical anisotropy demonstrated its paramount importance for light manipulation which resulted in numerous applications ranging from subdiffraction light guiding to switchable nanolasers. In spite of recent advances in the field, achieving continuous tunability of optical anisotropy remains an outstanding challenge. Here, we present a solution to the problem through chemical alteration of the ratio of halogen atoms (X = Br or Cl) in single-crystal CsPbX$_3$ halide perovskites. It turns out that the anisotropy originates from an excitonic resonance in the perovskite, which spectral position and strength are determined by the halogens composition. As a result, we manage to continually modify the optical anisotropy by 0.14. We also discover that the halide perovskite can demonstrate optical anisotropy up to 0.6 in the visible range -- the largest value among non-van der Waals materials. Moreover, our results reveal that this anisotropy could be in-plane and out-of-plane, depending on perovskite shape -- rectangular and square. Hence, it can serve as an additional degree of freedom for anisotropy manipulation. As a practical demonstration, we created perovskite anisotropic nanowaveguides and show a significant impact of anisotropy on high-order guiding modes. These findings pave the way for halide perovskites as a next-generation platform for tunable anisotropic photonics., Comment: 18 pages, 3 figures