Issue 5, 2026
Evaluation of memcapacitive properties of DPPC–CHOL lipid membrane by molecular dynamics
Evaluation of memcapacitive properties of DPPC–CHOL lipid membrane by molecular dynamics
I. I. Zlochevskiy$^1$, D. V. Zav’yalov$^1$
Coarse-grained molecular dynamics simulations using the Martini 2.2p force field were employed to investigate the effect of cholesterol (CHOL) on the memcapacitive properties of model lipid bilayers composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). Systems with different cholesterol mole fractions were considered, ranging from 0 to 400 CHOL molecules per 1024 lipids, in the presence of 1.5 M NaCl and an alternating electric field with amplitudes of 0.05, 0.10, and 0.15 V/nm. All investigated systems exhibited memcapacitive behavior regardless of cholesterol content, as evidenced by the nonlinear dependence of the surface charge density on the electric field strength and the presence of a characteristic hysteresis loop. An increase in the cholesterol fraction was accompanied by a decrease in the area of the σ(E) hysteresis loop, which characterizes the dissipative component of the electrical response of the membrane system under cyclic variation of the external electric field. Analysis of ion distributions showed that changes in cholesterol content were accompanied by changes in the local distributions of Na+ cations and Cl− anions in the vicinity of the membrane, which is associated with changes in the number of polar DPPC headgroups and the structural organization of the lipid bilayer. For the system containing DPPC alone, a deviation of the hysteresis loop from an elliptical shape was observed, indicating a more pronounced nonlinear character of the electrical response in the region near the membrane. Overall, the results demonstrate that cholesterol modulates the electrical response of the membrane by altering the redistribution of ions and the magnitude of dissipative losses under cyclic electric-field excitation. The results may be useful for further analysis of the influence of lipid composition on the electrical properties of membrane systems and their application in models of memcapacitors and neuromorphic materials.
Show AbstractA series-shunt MEMS switch for advanced radio electronics \\in the 1-20 GHz frequency range
A series-shunt MEMS switch for advanced radio electronics \\in the 1-20 GHz frequency range
M. O. Morozov$^{1,2}$, I. V. Uvarov$^2$
Modern communication systems have a growing need for miniature switching elements with high radio-frequency performance. A promising solution is switches based on microelectromechanical systems (MEMS). Conventional MEMS switches are typically based on series or shunt switching principle. The former typically operate in the 0-4 GHz range, while the latter operate at frequencies above 4 GHz, but also within a narrow band. This paper presents simulation results for a series-shunt MEMS switch with an operating bandwidth extended by more than 15 GHz.
Show AbstractExperimental study of the directivity patterns of emitters and receivers of airborne ultrasound in the frequency range of 25 - 40 kHz for the design of multi-element focusing systems
Experimental study of the directivity patterns of emitters and receivers of airborne ultrasound in the frequency range of 25 - 40 kHz for the design of multi-element focusing systems
N. G. Gogmachadze$^1$, E. A. Petrov$^1$, A. V. Lapina$^1$, S. A. Tsysar$^1$, O. A. Sapozhnikov$^1$
An experimental study of the directivity patterns of low-frequency ultrasound electroacoustic transducers in air, which are potential elements of a multi-element focused antenna, was conducted. The relevance of the study is due to the fact that the structure of the acoustic field in the focal region of a complex antenna array in linear mode is directly determined by the superposition of the fields of individual elements, whose far-field characteristics are described by their directivity patterns. In theoretical models, ultrasonic transducers (emitters and receivers) are often represented as an ideal circular piston in a rigid baffle, which allows the directivity pattern to be described by a first-order Bessel function. However, the actual characteristics of receiving and emitting devices may differ from this ideal model. In this paper, we compare the experimentally measured directivity patterns of low-frequency ultrasound transducers (25–40 kHz) with the directivity pattern of a circular piston in order to improve calibration accuracy and subsequently take these parameters into account when recording powerful nonlinear fields in air.
Show AbstractDevelopment of a new calibration scale for urine osmolality and density using a refractometer
Development of a new calibration scale for urine osmolality and density using a refractometer
J. A. Guseva$^1$, V. V. Davydov$^2$, D. S. Provodin$^2$, D. V. Davydova$^2$, M. A. Yakusheva$^3$
A new calibration scale has been developed for rapid determination of urine density and osmolality from the refractive index measured with a refractometer. Synchronous measurements of the refractive index n, density ρ, and osmolality Os were performed on the same urine samples from a control group in the temperature range 283–309 K, covering all physiologically relevant values. Using least-squares regression, the linear relationships constituting the new scale were obtained: ρ = 2.4147 n − 2.2379 (R2 = 0.9998) and Os = 36.68 ρ − 36.59 (R2 = 0.9995). The error of indirect osmolality determination from the refractive index, including temperature correction, is less than 2 mOsm/L, meeting the requirements of rapid diagnostics. An algorithm for converting measurements to the standard temperature of 293 K is proposed. The developed scale can be implemented in portable refractometers for early diagnosis of chronic kidney diseases in outpatient clinics and paramedic stations.
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