Magnetic Temporal Interference for Noninvasive Focal Brain Stimulation

Non-invasive stimulation of deep brain regions has been a major goal for neuroscience and neuromodulation in the past three decades. Transcranial magnetic stimulation (TMS), for instance, cannot target deep regions in the brain without activating the overlying tissues and has a poor spatial resolution. In this manuscript, we propose a new concept that relies on the temporal interference of two high-frequency magnetic fields generated by two electromagnetic solenoids. To illustrate the concept, custom solenoids were fabricated and optimized to generate temporal interfering electric fields for rodent brain stimulation. C-Fos expression was used to track neuronal activation. C-Fos expression was not present in regions impacted by only one high-frequency magnetic field indicating ineffective recruitment of neural activity in non-target regions. In contrast, regions impacted by two fields that interfere to create a low-frequency envelope display a strong increase in c-Fos expression. Therefore, this magnetic temporal interference solenoid-based system provides a framework to perform further stimulation studies that would investigate the advantages it could bring over conventional TMS systems.

Impact of Superconductors’ Properties on the Measurement Sensitivity of Resonant-Based Axion Detectors

Axions, hypothetical particles theorised to solve the strong CP problem, are presently being considered as strong candidates for cold dark matter constituents. The signal power of resonant-based axion detectors, known as haloscopes, is directly proportional to their quality factor Q. In this paper, the impact of the use of superconductors on the performances of haloscopes is studied by evaluating the obtainable Q. In particular, the surface resistance Rs of NbTi, Nb3Sn, YBa2Cu3O7−δ, and FeSe0.5Te0.5 is computed in the frequency, magnetic field, and temperature ranges of interest, starting from the measured vortex motion complex resistivity and the screening lengths of these materials. From Rs, the quality factor Q of a cylindrical haloscope with copper conical bases and a superconductive lateral wall, operating with the TM010 mode, is evaluated and used to perform a comparison of the performances of the different materials. Both YBa2Cu3O7−δ and FeSe0.5Te0.5 are shown to improve the measurement sensitivity by almost an order of magnitude, with respect to a whole Cu cavity, while NbTi is shown to be suitable only at lower frequencies (<10 GHz). Nb3Sn can provide an intermediate improvement of the whole spectrum of interest.

Permeability of the Composite Magnetic Microcapsules Triggered by a Non-Heating Low-Frequency Magnetic Field

Nanosystems for targeted delivery and remote-controlled release of therapeutic agents has become a top priority in pharmaceutical science and drug development in recent decades. Application of a low frequency magnetic field (LFMF) as an external stimulus opens up opportunities to trigger release of the encapsulated bioactive substances with high locality and penetration ability without heating of biological tissue in vivo. Therefore, the development of novel microencapsulated drug formulations sensitive to LFMF is of paramount importance. Here, we report the result of LFMF-triggered release of the fluorescently labeled dextran from polyelectrolyte microcapsules modified with magnetic iron oxide nanoparticles. Polyelectrolyte microcapsules were obtained by a method of sequential deposition of oppositely charged poly(allylamine hydrochloride) (PAH) and poly(sodium 4-styrenesulfonate) (PSS) on the surface of colloidal vaterite particles. The synthesized single domain maghemite nanoparticles integrated into the polymer multilayers serve as magneto-mechanical actuators. We report the first systematic study of the effect of magnetic field with different frequencies on the permeability of the microcapsules. The in situ measurements of the optical density curves upon the 100 mT LFMF treatment were carried out for a range of frequencies from 30 to 150 Hz. Such fields do not cause any considerable heating of the magnetic nanoparticles but promote their rotating-oscillating mechanical motion that produces mechanical forces and deformations of the adjacent materials. We observed the changes in release of the encapsulated TRITC-dextran molecules from the PAH/PSS microcapsules upon application of the 50 Hz alternating magnetic field. The obtained results open new horizons for the design of polymer systems for triggered drug release without dangerous heating and overheating of tissues.

Analytical solution of problem of shielding low-frequency magnetic field by thin-walled cylindrical screen in presence of cylinder

The analytical solution of boundary value problem describing the process of penetration of low-frequency magnetic field through thin-walled cylindrical screen with cylindrical inclusion is constructed by use of approximate boundary conditions. The source of the field is a thin thread of infinitely small length with an infinitely small cross-section where current circulates. Thread is located in a plane which is perpendicular to axis of cylindrical screen, in outer region with respect to a screen. Initially the potential of initial magnetic field is represented as spherical harmonic functions, then using addition theorems connecting spherical and cylindrical harmonic functions, it became as cylindrical harmonic functions superposition. Secondary potentials of magnetic field are also presented as superposition of cylindrical harmonic functions in three-dimensional space. It is shown that the solution of formulated boundary value problem is reduced to the solution of linear algebraic equations system for coefficients included in the representation of secondary fields. The influence of some aspects of the problem on the value of the screening coefficient of an external magnetic field when passing through a cylindrical copper screen in the presence of a cylindrical inclusion is studied numerically. Calculation results are presented in graphs form. Obtained results can be used to shield technical devices and biological objects against the effects of magnetic fields to provide ecological surrounding of operating electrical installations and devices.

Pengaruh Paparan Medan Magnet Extremely Low Frequency (ELF) terhadap Perubahan pH Pada Proses Fermentasi Biji Kopi Lanang (Peaberry) Kering

ABSTRAK Kopi lanang (Peaberry) merupakan jenis kopi yang mempunyai biji berkeping satu (monokotil) dengan kafein yang kadarnya lebih tinggi jika dibandingkan dengan kopi jenis lain. Kadar kafein yang tinggi pada biji kopi bisa diturunkan dengan proses fermentasi kopi. Penelitian ini mempunyai tujuan untuk mengetahui pengaruh paparan medan magnet ELF (Extremely Low Frequency) terhadap perubahan pH pada proses fermentasi biji kopi lanang (Peaberry) kering jenis robusta dengan penambahan enzim -amilase. Jenis penelitian yang digunakan yaitu penelitian eksperimen dengan desain Rancangan Acak Lengkap (RAL) bertujuan mengkaji pengaruh perlakuan dengan pengulangan percobaan. Penelitian ini memiliki tujuh kelompok sampel meliputi kelompok kontrol dan kelompok eksperimen variasi intensitas paparan medan manet ELF sebesar 200 µT dan 300 µT dan variasi lama pemaparan 30 menit, 60 menit dan 90 menit. Pengukuran data hasil penelitian diambil setelah pemaparan yaitu pada hari ke-1 sampai hari ke-5 selama proses fermentasi berlangsung. Hasil penelitian menyatakan bahwa paparan medan magnet ELF berpengaruh terhadap perubahan pH pada proses fermentasi biji kopi lanang (Peaberry) kering jenis robusta yang ditunjukkan dengan variasi bentuk grafik. Pemaparan medan magnet ELF dengan intensitas 200 µT dan lama pemaparan 30 menit dapat menurunkan pH secara signifikan, sedangkan intensitas 200 µT dan lama waktu paparan 90 menit dapat menaikkan pH secara signifikan pada proses fermentasi biji kopi lanang (Peaberry) kering jenis robusta. Kata kunci : Medan magnet ELF, Fermentasi, Kopi Lanang (Peaberry), pH ABSTRACT Peaberry coffee is a type of coffee that has a single bean (monocotyle) with a higher levels of caffeine if compared whith other types of coffee. High levels of caffeine in coffee beans can be reduced by the coffee fermentation process. The study aims to examine the effect of exposure to the ELF (Extremely Low Frequency) magnetic field on changes of pH in the fermentation process of robusta peaberry dray coffee beans with the addition of -amylase enzyme. The type of research that use in the experimental reseacrh with a randomized subject post test only control grup design, it aiming to examine the effect of treatment by repeating the experiment. This study include seven sample groups covering the control group and the experimental group variation in the intensity of ELF magnetic field with 200 µT and 300 µT and variation of a length 30, 60, 90 minutes. Meansurement of the data research taken after exposure that is on the day one to day five during the fermentation process. The result of the study suggest that exposure to ELF magnetic field has an effect on the pH fermentation prosess of dried peaberry coffee beans, which was shown variations of the shape of the graph. Exposure to the ELF magnetic field with an intensity of 200 µT and the length of 30 minutes can significantly decrease the pH, while the intensity of 200 µT and the length of 30 minutes can significantly increase the pH in the fermentation process of dried robusta paberry coffee beans. Keywords : ELF magnetic field, Fermentation, Peaberry Coffee, pH