Fields Of Different Frequencies Research Articles

Molecular dynamics of deformation and fragmentation processes in liquid droplets under pulsed electric field

The deformation and breakup of droplets are widely observed in various aspects of production and daily life. Using molecular dynamics simulations, this study primarily investigated the deformation and breakup of droplets in a nitrogen environment under pulsed electric fields of different frequencies. The results indicate that the droplet deformation undergoes periodic changes under the influence of the pulsed electric field. At equivalent electric field strengths, droplets are more likely to break under a 6.25 GHz pulsed electric field compared to a 25 GHz pulsed electric field, where droplet deformation remains stable without breaking. At every frequency, the bond energy of water molecules consistently decreases. The solvent-accessible surface area changes with the electric field at 6.25 GHz. Furthermore, the minimum value of hydrogen bond quantity reached under high-frequency pulsed fields is higher than that under low-frequency fields. The change in hydrogen bond quantity is inversely proportional to the solvent-accessible surface area. These findings provide insights into the microscopic mechanisms of droplet deformation and breakup, offering a reference for future studies.

EXPERIMENTAL STUDIES OF NOISE POLLUTION OF MECHANICAL PROCESSING PLANTS

Purpose. Determination of noise pollution at the workplace of workers of metal-cutting machines of turning, milling and drilling groups. Methodology. An experimental study of the noise load at the workplace of workers working on lathes, milling and drilling group machines. The research was carried out using a testo 816-1 digital noise level meter, Sound Forge Pro software and a mathematical package for the formation of noise dependences on the type and mode of operation of the machines. Results. An experimental study of the noise load at the workplace of workers working on metal-cutting machines, namely universal lathe-screw-cutting machines (type 1K62 and CA6136), vertical milling machines (type 6P11A and F2-250), vertical milling machine with CNC (type XS5036C) and radial drilling machine (type 2L53U). In addition, it was established that the type of machine affects the level of noise pollution at the workplace of metal-cutting machine workers. For example, the machines used for drilling are characterized by high noise values in all octave frequency ranges and all operating modes, increasing the noise level by 15 dB (16.5%) on average. Milling machines, compared to lathes, show higher noise values at medium and high octave frequencies by 7 dB (8.4%). Based on the results of the study, an adequate polynomial dependence of the fifth order was determined, which describes the noise levels relative to the frequency and corresponds to the results of the natural experiment. The resulting dependencies have practical applications in the development of component materials for simultaneous shielding of both magnetic fields of an electromagnetic field of industrial frequency and electromagnetic fields of different frequencies. Scientific novelty. The solution of this problem can be used in the future to assess the risk of occupational diseases among workers working at mechanical processing stations. Practical significance. The determined dependence will allow further consideration of the issue related to the protection of employees of mechanical processing stations from noise pollution arising during the operation of metal-cutting machines of various groups. Key words: railway, metalworking machine, noise pollution, noise.

Changes in myelinated nerve fibers induced by pulsed electrical stimulation: A microstructural perspective on the causes of electrical stimulation side effects

Electrical brain stimulation technology is widely used in the clinic to treat brain neurological disorders. However, during treatment, patients may experience side effects such as pain, poor limb coordination, and skin rash. Previous reports have focused on the brilliant chapter on electrical brain stimulation technology and have not paid attention to patients' suffering caused by side effects during treatment. In this study, electrodes were arranged on the medulla oblongata. Pulsed electric fields of different frequencies were used to perform electrical stimulation to study the impact of electric fields on myelinated nerve fibers and reveal the possible microstructural origin of side effects. Transmission electron microscopy was used to analyze and quantify the changes in microstructure. The results illustrated that myelinated nerve fibers underwent atrophy under pulsed electric fields, with the mildest degree of atrophy under high-frequency (400 Hz) electric fields. Myelin sheaths experienced plate separation under pulsed electric fields, and a distinct laminar structure appeared. The microstructure changes may be related to the side effects of clinical electrical stimulation. This study can provide pathological possibilities for exploring the causes of the side effects of electrical stimulation and supply guidance for selecting electrical parameters for clinical electrical stimulation therapy from a distinctive perspective.

Regulation of local alternating electric fields on synaptic plasticity in brain tissue.

External electric fields can regulate the neural network and change the excitability of the in-vivo cerebral cortex. Here, to prove the effect of alternating electric fields on the synaptic plasticity of ex-vivo tissues, the regular changes in the synaptic structure under alternating electric fields were studied. This study applied alternating electric fields with a peak voltage of 20V and frequencies of 5, 20, 50, and 80Hz to the porcine cerebral cortex. Relying on transmission electron microscopy (TEM), the ultrastructure of synapses was observed, and the curvature radius of post-synaptic density (PSD) and the synaptic gap distance was quantified. The results indicated that under alternating electric fields, the average synaptic curvature of the PSD decreased by 30-59% with increasing frequency, and the average synaptic gap distance became narrower. In ex-vivo brain tissue, synaptic plasticity can be regulated by alternating electric fields of different frequencies. This study can provide reference data for the storage and regulation of ex-vivo organs, as well as comparable data for in-vivo studies.

Influence of electromagnetic fields of different frequencies on biological objects. Review = Вплив електромагнітних полів різних частот на біологічні об'єкти. Огляд літератури

Influence of electromagnetic fields of different frequencies on biological objects. Review = Вплив електромагнітних полів різних частот на біологічні об'єкти. Огляд літератури

Controlling the electrostatic Faraday instability using superposed electric fields

We present an experimental study of the electrostatic Faraday instability at the interface between a dielectric and a conducting liquid. We study the response of the interface to an ac electric field, which is superposed by either a second ac field of different frequency, or by a dc field. An important control parameter is the mixing ratio, which denotes the relative amplitudes of the different components of the driving signal. For ac/ac driving, gradual variations of the mixing ratio can induce a jump of the pattern wavelength, and for ac/dc driving, the response wavelength can be tuned continuously by adjusting the mixing ratio.

Frequency-Specific Modulation of Slow-Wave Neural Oscillations via Weak Exogeneous Extracellular Fields Reveals a Resonance Pattern.

Single neurons often exhibit endogenous oscillatory activity centered around a specific frequency band. Transcranial alternating current stimulation (tACS) can generate a weak oscillating extracellular field in the brain that causes subthreshold membrane potential shifts that can affect spike timing at the single neuron level. Many studies have now shown that the endogenous oscillation can be entrained when the tACS frequency matches that of the exogenous extracellular field. However, the effect of tACS on the amplitude of the endogenous oscillation has been less well studied. We investigated this by using exogenous extracellular fields to modulate slow-wave neural oscillations in the ketamine anesthetized male Wistar rat. We applied spatially broad extracellular fields of different frequencies while recording spiking activity from single neurons. The effect of the exogenous extracellular field on the slow-wave neural oscillation amplitude (NOA) followed a resonance pattern: large modulations were observed when the extracellular frequency matched the endogenous frequency of the neuron, while extracellular fields with frequencies far away from the endogenous frequency had little effect. No changes in spike-rate were observed for any of the extracellular fields applied. Our results demonstrate that in addition to the previously reported entrainment and Arnold tongue patterns, weak oscillating extracellular fields modulate the amplitude of the endogenous neural oscillation without any changes in spike-rate, and that this modulation follows a frequency-specific resonance pattern.SIGNIFICANCE STATEMENT Neural activity often oscillates around specific endogenous frequencies. Transcranial alternating current stimulation (tACS) is a neuromodulation method which biases spike-times and alter endogenous activity. Most tACS studies focus on entrainment effects which occur when tACS and endogenous neural frequencies are matched. In this study we varied the frequency of the applied tACS and investigated its effect on amplitude of the neural oscillation. Our results revealed a resonance pattern where tACS frequencies close to the endogenous frequency caused an increase in neural oscillation amplitude (NOA) specifically at the applied tACS frequency, while applying tACS frequencies farther away caused little or no change in NOA. Furthermore, applying tACS at differing frequencies caused the amplitude of the neural oscillation at the prestimulation endogenous frequency to decrease.

Disordered ensembles of strongly coupled single-molecule plasmonic picocavities as nonlinear optical metamaterials.

We propose to use molecular picocavity ensembles as macroscopic coherent nonlinear optical devices enabled by nanoscale strong coupling. For a generic picocavity model that includes molecular and photonic disorder, we derive theoretical performance bounds for coherent cross-phase modulation signals using weak classical fields of different frequencies. We show that strong coupling of the picocavity vacua with a specific vibronic sideband in the molecular emission spectrum results in a significant variation of the effective refractive index of the metamaterial relative to a molecule-free scenario due to a vacuum-induced Autler-Townes effect. For a realistic molecular disorder model, we demonstrate that cross-phase modulation of optical fields as weak as 10 kW/cm2 is feasible using dilute ensembles of molecular picocavities at room temperature, provided that the confined vacuum is not resonantly driven by the external probe field. Our work paves the way for the development of plasmonic metamaterials that exploit strong coupling for optical state preparation and quantum control.

Space-Charge Characteristics in Epoxy Composites Under Square Pulse Wave of Different Polarities With Various Frequencies at Various Temperatures

Space-charge characteristics of the pure epoxy resin (EP) and epoxy-based hybrid composites under square pulse waves of different polarities and frequencies at different temperatures are investigated. A specially built high-speed pulsed electro-acoustic (PEA) equipment for high-temperature testing is used. The square pulse of 40 kV/mm with different polarities and frequencies at 25 °C, 50 °C, and 80 °C, respectively, are adopted. The findings reveal that a negative electric field with a greater frequency and a positive electric field with a lower frequency can increase the space-charge accumulation. At low temperatures, there is no noticeable difference between the pure epoxy and micro-nano hybrid (MN) samples. The MN sample has fewer accumulated charges than the pure epoxy sample under the same electric field of different frequencies at different temperatures. At different temperatures, the electric field inside the pure epoxy sample distorts more severely than the MN sample, and such distortion increases with the temperature. On the other side, the electric field in the MN sample remains steady even at high temperatures. Negative electric fields have a more significant impact on average charge amounts than positive electric fields, especially at higher frequencies. A relevant mechanism is proposed to explain the results.

Study on the magnetic field influence around of the overhead power lines regarding the general public exposure level

This paper analyzes the distribution of the dimensions of the magnetic field in the vicinity of the high voltage overhead power lines (400 kV), in the context in which the effects of the electromagnetic field on living organisms and especially on humans are currently being analyzed. Electromagnetic fields of different frequencies interact with the human body in different ways, just as the effects of low frequency fields are not the same as those of the high frequency fields. Analysis of the electromagnetic field values near a high voltage overhead power line is very important for determining the degree of exposure to the electromagnetic field. The measurements are performed with the magnetic field tester, Hioki FT 3470-50 and the values obtained are compared with those indicated by current standards.

Vector Magnetic Properties of Electrical Steel Sheet Under DC-Biased Flux and Rotating Magnetic Fields of Varying Frequencies

In this study, we explore the vector magnetic properties of the electrical steel sheet under dc-biased flux and rotating magnetic field of different frequencies. The corresponding iron loss and the rotational eddy current loss are discussed. An enhanced vector magnetic hysteresis model is proposed to describe the B- H behavior under these conditions. The accuracy of the proposed model is verified by the close agreement between the hysteresis loops calculated with the proposed model and those measured experimentally, as well as by the neglectable calculation error of the total iron loss.

Group Velocity Modulation and Light Field Focusing of the Edge States in Chirped Valley Graphene Plasmonic Metamaterials.

The valley degree of freedom, like the spin degree of freedom in spintronics, is regarded as a new information carrier, promoting the emerging valley photonics. Although there exist topologically protected valley edge states which are immune to optical backscattering caused by defects and sharp edges at the inverse valley Hall phase interfaces composed of ordinary optical dielectric materials, the dispersion and the frequency range of the edge states cannot be tuned once the geometrical parameters of the materials are determined. In this paper, we propose a chirped valley graphene plasmonic metamaterial waveguide composed of the valley graphene plasmonic metamaterials (VGPMs) with regularly varying chemical potentials while keeping the geometrical parameters constant. Due to the excellent tunability of graphene, the proposed waveguide supports group velocity modulation and zero group velocity of the edge states, where the light field of different frequencies focuses at different specific locations. The proposed structures may find significant applications in the fields of slow light, micro–nano-optics, topological plasmonics, and on-chip light manipulation.

Lens mediated scattering of sound by sound with finite aperture beams.

An experimental concept for measuring sound-sound scattering of finite aperture acoustic beams in a water tank facility is presented. In order to achieve a measurable effect, the beams are collimated within their intersection domain by a focusing acoustic lens. A paraxial quasi-linear split step simulation tool has been developed and used in order to determine and optimize experiment setup parameters. The scattered part of the difference frequency field was measured and found to be compatible with simulations. Furthermore, the primary beams were also monitored in order to guarantee full compatibility with simulated propagation and compare the measured difference field with the overlap contribution. A spatially coherent post processing filtering was applied in order to improve the signal to noise ratio. A distinct clear scattering peak in the difference field has been identified propagating with the predicted off axis tilt angle.

РОЗРАХУНКОВІ МЕТОДИ ПРОЕКТУВАННЯ ЕЛЕКТРОМАГНІТНИХ ЕКРАНІВ ІЗ ЗАДАНИМИ ЗАХИСНИМИ ВЛАСТИВОСТЯМИ

На сьогоднішній день основна частина досліджень та прикладних розробок щодо розроблення матеріалів для екранування електромагнітних полів різних частотних діапазонів є експериментальними, особливо це стосується сучасних композиційних матеріалів. Встановлено, що актуальною є задача вироблення раціональної методології розрахункового прогнозування ефективності матеріалів для екранування електромагнітних полів. Мета роботи − надання зручного у використанні розрахункового апарату для прогнозування захисних властивостей матеріалів для екранування електромагнітних полів, що дозволить мінімізувати обсяги експериментальних робіт під час проектування захисних конструкцій. Наведено, виходячи з фундаментальних співвідношень електродинаміки суцільних середовищ, зручні у використанні залежності коефіцієнтів екранування металевих та композиційних матеріалів від їх геометричних, магнітних та електрофізичних властивостей. Обґрунтовано співвідношення щодо визначення внеску відбиття електромагнітних хвиль у загальний коефіцієнт екранування. Це дозволяє розрахувати товщину електромагнітного екрана на принципах розумної достатності. Показано, що для ефективного використання розрахункових методів оцінювання захисних властивостей композиційних матеріалів для екранування магнітних та електромагнітних полів потрібна наявність надійних експериментальних даних щодо магнітних та електрофізичних властивостей найбільш поширених за складом композиційних матеріалів

Frequency-Domain Quantum Interference with Correlated Photons from an Integrated Microresonator.

Frequency encoding of quantum information together with fiber and integrated photonic technologies can significantly reduce the complexity and resource requirements for realizing all-photonic quantum networks. The key challenge for such frequency domain processing of single photons is to realize coherent and selective interactions between quantum optical fields of different frequencies over a range of bandwidths. Here, we report frequency-domain Hong-Ou-Mandel interference with spectrally distinct photons generated from a chip-based microresonator. We use four-wave mixing to implement an active "frequency beam splitter" and achieve interference visibilities of 0.95±0.02. Our work establishes four-wave mixing as a tool for selective high-fidelity two-photon operations in the frequency domain which, combined with integrated single-photon sources, provides a building block for frequency-multiplexed photonic quantum networks.

Эффективность метода обработки быстрыми электронами для снижения порчи растительного сырья при хранении и транспортировке

Актуальной и не до конца решенной в настоящее время является проблема снижения потерь пищевого сырья и продовольственных товаров при транспортировке и хранении, снижения качества продукции в результате заражения насекомыми и микроорганизмами, порчи продукции грызунами. Применение традиционных методов дезинфекции, дезинсекции и дератизации не всегда бывает достаточным для полного обеззараживания, а иногда и нецелесообразным, и требуется использование альтернативных способов, например воздействие электромагнитных полей различного частотного диапазона. Из всего спектра электромагнитных волн исследователи особо выделяют ионизирующее излучение, способное убивать или видоизменять клетки растений, фрагментировать ДНК. Это свойство ионизирующего излучения можно использовать для борьбы с микроорганизмами, насекомыми, гельмитами и грызунами. Настоящая работа является развитием научных идей академика РАН И.А. Рогова в области использования ионизирующих излучений для обработки сельскохозяйственного сырья и продуктов питания. В статье приведены результаты экспериментов по обработке быстрыми электронами пищевого сырья и продуктов, зараженных микроорганизмами и насекомыми. Для различных объектов исследования определены дозы воздействия, вызывающие хороший биологический эффект, но не приводящие к деструкции биополимеров. Показано, что помимо дозы, другие факторы оказывают значительное воздействие на результаты процесса обработки, например температура и физическое состояние пищи. Замораживание оказывает защитное влияние во время облучения, предупреждая образование продуктов водного радиолиза, которые образуются в результате реакции с субстратом. При нагревании эти продукты (гидроксильные радикалы) имеют тенденцию реагировать преимущественно друг с другом, а не с субстратом, так что опасность для последнего обычно уменьшается, когда производят облучение замороженной пищи. Анаэробные условия также влияют на природу радиолитических продуктов, поскольку присутствие кислорода во время облучения может генерировать высокореактивные супероксидные радикалы и пероксирадикалы и пероксид водорода. Поведен сравнительный анализ результатов действия различных доз облучения на продукты растительного и животного происхождения. Показана эффективность и экономическая целесообразность применения обработки быстрыми электронами для снижения микробиальной порчи и зараженности насекомыми пищевого сырья и продовольсвенных товаров, а также для увеличения сроков хранения продукции.

A versatile computational approach for the numerical modelling of parametric acoustic array.

This work presents a versatile computational approach for the numerical modelling of a parametrically generated low-frequency sound. The proposed method is based on the quasi-linear approximation, and it does not employ the paraxial approximation. The primary acoustic field is calculated by the Rayleigh integral or the boundary element method; the secondary difference-frequency field is calculated by the finite element method. As governing wave equations, a general second-order wave equation for acoustic pressure, the Westervelt equation, and Kuznetsov equation are tested, and the corresponding numerical results are compared. The proposed approach allows studying the near-field, far-field, as well as the off-axis field of the difference-frequency wave parametrically radiated from complex emitters. As numerical examples, parametric radiation from a baffled piston and a piston combined with a horn are examined.

P11.25 Assessing electrical properties of cells as predictive marker for patient-specific TTFields response and optimal frequency

Abstract BACKGROUND Tumor treating fields (TTFields) are currently approved for the treatment of glioblastoma multiforme (GBM, using 200 kHz), and being tested in other tumor types such as non-small cell lung cancer and brain metastases occurring in this indication (LUNAR and METIS trials, using 150 kHz). Response to TTFields in cancer cells was empirically shown to be frequency-dependent specific for cell type; however, there are no markers available predicting optimal frequency or response in different cancer types or individual patients to date. There is evidence indicating electrical properties determine the optimal anti-mitotic frequency. This study analyzed the correlation of electrical properties of cells with their optimal TTFields frequency and sensitivity using the 3DEP reader (LabTech) to determine the electrical properties with the help of Dielectrophoresis (DEP) force. With this technique, cell movements within electric fields of different frequencies can by analyzed based on the physical effect of DEP, exercising a force on polarizable particles inside a non-homogeneous electric field. MATERIAL AND METHODS We used the 3DEP reader to obtain baseline properties (permittivity and conductivity) of 17 different cell lines of several tumor types. The resulting curves were analyzed by a 2-way ANOVA. Additionally, we determined the optimal frequency for maximum cytotoxic effect for each cell line using the inovitroTM system and eventually compared with the detected electrical properties. RESULTS We found cell lines with an optimal TTFields frequency of 150 kHz (corresponding to cells with a membrane capacitance in the lower range of the observed 3DEP curves, n=9) to possess significantly different (p<0.001) electrical properties from cells with an optimal TTFields frequency of 200 kHz (n=8). According to the curve differences in the lower frequency range, the measure of membrane capacitance served as a good predictor for TTFields response. CONCLUSION This study showed a correlation of cell membrane capacitance and optimal TTFields frequency and response. Our results provide a substantial rationale for further studies investigating the predictive potential of electrical properties of tumor cells as a measure for the optimal frequency and sensitivity to TTFields in individual patients.

Switchable slow light rainbow trapping and releasing in strongly coupling topological photonic systems

We design and present a switchable slow light rainbow trapping (SLRT) state in a strongly coupling topological photonic system made from a magneto-optical photonic crystal waveguide channel. The waveguide channel supports slow light states with extremely small group velocity (vg=2.1×10−6c), low group-velocity dispersion, and a broadband operation bandwidth (3.60–4.48 GHz, near 22% of bandwidth). These slow light states originate from the strong coupling between two counter propagating topological photonic states. Under a gradient magnetic field, different frequency components of a wave packet are separated and stored at different positions for a long temporal duration with high spatial precision (without crosstalk and overlap between the electric fields of different frequencies) to form SLRT. Besides, these SLRT states can be easily switched among the forbidden state, trapped state, and releasing state by tuning the external magnetic field. The results suggest that the topological photonic state can offer a precise route of spatial-temporal-spectral control upon a light signal and find applications for optical buffers, broadband slow light systems, optical filters, wavelength-division multiplexing, and other optical communication devices.

Successful Tumor Electrochemotherapy Using Sine Waves

The purpose of this work is to assess the ability of sine waves to perform electrochemotherapy (ECT) and to study the dependence of the frequency of the applied sine wave on the treatment efficacy. A subcutaneous tumor model in mice was used, and the electric field was delivered in combination with bleomycin. Sinusoidal electric fields of different frequencies, amplitudes, and durations were compared to square waves. Computer simulations were additionally performed. The results confirmed the ability of a sinusoidal electric field to obtain successful ECT responses. A strong dependence on frequency was obtained. The efficacy of the treatment decreased when the frequency of the sine waves was increased. At low sinusoidal frequency, the efficacy of the treatment is very similar to that obtained with a square wave. The collateral effects such as skin burns and muscle contractions decreased for the highest frequency assayed. The use of sine wave burst represents a feasible option for the treatment of cancer by ECT. These results could have important implications for the treatment of cancer in the clinical world where ECT is performed with dc square pulses.