Observation of Supercavity Modes in Subwavelength Dielectric Resonators

Electromagnetic response of dielectric resonators with high refractive index is governed by optically induced electric and magnetic Mie resonances facilitating confinement of light with the amplitude enhancement. Traditionally, strong subwavelength trapping of light was associated only with plasmonic or epsilon‐near‐zero structures, which however suffer from material losses. Recently, an alternative localization mechanism was proposed allowing the trapping of light in individual subwavelength optical resonators with a high quality factor in the regime of a supercavity mode. Here, the experimental observation of the supercavity modes in subwavelength ceramic resonators in the radio‐frequency range is presented. It is experimentally demonstrated that the regime of supercavity modes can be achieved via precise tuning of the resonator's dimensions. A huge growth of the unloaded quality factor is achieved with experimental values up to 1.25 × 10⁴, limited only by material losses of ceramics. It is revealed that the supercavity modes can be excited efficiently both in the near‐ and far‐field. In both cases, the supercavity mode manifests itself explicitly as a Fano resonance with characteristic peculiarities of spectral shape and radiation pattern. A comparison of supercavities made of diversified materials for the visible, infrared, THz, and radio‐frequency regimes is provided.     

Heart Rate Extraction from Vowel Speech Signals

This paper presents a novel non-contact heart rate extraction method from vowel speech signals.The proposed method is based on modeling the relationship between speech production of vowel speech signals and heart activities for humans where it is observed that the moment of heart beat causes a short increment(evolution) of vowel speech formants.The short-time Fourier transform(STFT) is used to detect the formant maximum peaks so as to accurately estimate the heart rate.Compared with traditional contact pulse oximeter,the average accuracy of the proposed non-contact heart rate extraction method exceeds 95%.The proposed non-contact heart rate extraction method is expected to play an important role in modern medical applications.     

Size driven thermodynamic crossovers in phase stability in zirconia and hafnia

Hafnia (HfO₂) and zirconia (ZrO₂) are of great interest in the quest for replacing silicon oxide in semiconductor field effect transistors because of their high permittivity. Both exhibit extensive polymorphism and understanding the energetics of their transitions is of major fundamental and practical importance. In this study, we present a systematic thermodynamic summary of the influence of particle size on thermodynamic phase stability in hafnia and zirconia using recently measured enthalpy data from the literature. The amorphous phase is found to be the most energetically stable above 165 and 363 m²/g of surface area for HfO₂ and ZrO₂, respectively. Below 16 and 20.3 m²/g of surface area, respectively, the monoclinic phase is the most energetically stable for HfO₂ and ZrO₂. At intermediate sizes there are closely balanced energetics among monoclinic, tetragonal, and cubic phases. The energy crossovers reflect decreasing surface enthalpy in the order monoclinic, tetragonal, cubic and amorphous for both hafnia and zirconia.     

Composition dependence of the electro-optic properties of iron-doped lithium niobate crystals mounted as bulk modulator

In this contribution, we report a complete set of electro-optic coefficients of iron-doped lithium niobate as function of the composition varying from sub-congruent to near-stoichiometric in a series of four crystals. The concentration of iron is constant for all crystals of the series. The electro-optic measurements of the r₂₂ and r_c coefficients were performed on a Sènarmont ellipsometric setup while those of r₁₃ and r₃₃ were performed on a Mach-Zehnder interferometric setup, by adaptation of the same frequency doubling electro-optic modulation and the MDM methods implemented in both electro-optical arrangements. The corresponding dielectric permittivities ε₁₁ and ε₃₃ as a function of composition were also determined. All electro-optic coefficients reveal a small change with composition, but significant above the experimental error. The nonmonotonous dependences of all electro-optic coefficients are found to be closely linked to their corresponding dielectric permittivities.     

Residual porosity and optical properties of spark plasma sintered transparent polycrystalline cerium-doped YAG

Transparent cerium-doped yttrium aluminum garnet (Ce:YAG) phosphors are promising candidates for high-power white light emitting diode applications. In the present study, Ce:YAG powder was synthesized by a co-precipitation method and highly transparent ceramics were fabricated by spark plasma sintering. The effects of temperature and pressure, as well as post-sintering treatments (annealing or hot isostatic pressing), on residual porosity were studied by electron and confocal laser microscopy. Correlation between residual porosity characteristics (pore size and volume fraction) and optical properties (in-line transmittance and photoluminescence intensity) of the luminescent transparent ceramics was established.     

The toolbox for local and global plagiarism detection

Digital plagiarism is a problem for educators all over the world. There are many software tools on the market for uncovering digital plagiarism. Most of them can work only with text submissions. In this paper, we present a new architecture for a plagiarism detection tool that can work with many different kinds of digital submissions, from plain or formatted texts to audio podcasts. The open architecture is based on converting the digital submission into text form for processing by a plagiarism detection algorithm. To process non-text submissions, the system is extended with the appropriate converter. Such an open architecture makes the anti-plagiarism toolbox universal and easily adaptable for processing virtually any kind of digital submissions. This paper describes a software prototype based on the proposed architecture and presents the results of its implementation on a large archive of student papers.     

SGLT2 Inhibitor Empagliflozin Modulates Ion Channels in Adult Zebrafish Heart

Empagliflozin, an inhibitor of sodium-glucose co-transporter 2 (iSGLT2), improves cardiovascular outcomes in patients with and without diabetes and possesses an antiarrhythmic activity. However, the mechanisms of these protective effects have not been fully elucidated. This study aimed to explore the impact of empagliflozin on ion channel activity and electrophysiological characteristics in the ventricular myocardium. The main cardiac ionic currents (I_Na, I_CaL, I_CaT, I_Kr, I_Ks) and action potentials (APs) were studied in zebrafish. Whole-cell currents were measured using the patch clamp method in the isolated ventricular cardiomyocytes. The conventional sharp glass microelectrode technique was applied for the recording of APs from the ventricular myocardium of the excised heart. Empagliflozin pretreatment compared to the control group enhanced potassium I_Kr step current density in the range of testing potentials from 0 to +30 mV, I_Kr tail current density in the range of testing potentials from +10 to +70 mV, and I_Ks current density in the range of testing potentials from −10 to +20 mV. Moreover, in the ventricular myocardium, empagliflozin pretreatment shortened AP duration APD as shown by reduced APD50 and APD90. Empagliflozin had no influence on sodium (I_Na) and L- and T-type calcium currents (I_CaL and I_CaT) in zebrafish ventricular cardiomyocytes. Thus, we conclude that empagliflozin increases the rapid and slow components of delayed rectifier K⁺ current (I_Kr and I_Ks). This mechanism could be favorable for cardiac protection.     

Mathematical modeling of heat transfer processes of coal waste combustion in a chamber of automated energy generating complex

The automated energy generating complex allows obtaining heat energy from waste coal-water slurry fuel (WCF) that is a mixture of fine coal particles from coal enrichment wastes with water. The mixture is blown into the swirl chamber under the pressure through the special sprayers. The received heat energy is used in different ways. One of the important issues is to estimate the heat losses through the walls of this chamber. In this paper we solved the boundary problem of mathematical physics to estimate the temperature fields in the walls of the swirl chamber. The obtained solution allows us to estimate the heat losses through the walls of the swirl chamber. The task of the mathematical physics has been solved by a numerical finite-difference method. The method for solving this problem can be used in the calculation of temperature fields and evaluation of heat losses in other thermal power units.