# Sensitivity of Cell Cultures on Time-Varying Low-Frequency Magnetic Field Changes
## 1 Introduction
The fields needed to explain the opening of a membrane channel protein are unrealistically high. On the other hand, models based on magnetic interactions can easily obtain a large enough signal-to-noise ratio because the level of magnetic thermal noise in tissue is low. The reason these models work is the same reason that makes the MRI technique possible.\"_  
[PERSON]'s IPR model as a plausible mechanism of LF MF action on biological structures inspires many experimental works [18; 23; 24; 25; 28; 29]. The principle is in the application of a parallel combination of static and time-varying MF, represented by their magnetic flux densities \(B_{\text{DC}}\) and \(B_{\text{AC}}\). The IPR postulates that in living cells a protein-bound ion of mass \(m\) and charge \(q\) can be targeted by the correct application of static and time-varying MF with a corresponding frequency (cyclotron frequency of the targeted ion), which is calculated as:  
\[f_{c}=\frac{1}{n}\frac{1}{2\pi}\frac{q}{m}B_{\text{DC}}, \tag{1}\]  
where \(q\) represents the ion's electric charge, \(m\) represents the molecular mass of the target ion, and the magnetic flux density of static MF, for the purpose of this paper the geomagnetic one, is represented by the value \(B_{\text{DC}}\). Within the scope of the presented paper, the targeted ion is calcium \({}^{40}\)Ca\({}^{2+}\) with a cyclotron frequency of 29.89 Hz. In accordance with IPR predictions, the strongest reaction should be expected at the \(B_{\rm AC}/B_{\rm DC}\) ratio of 1.8. In mentioned work by [PERSON] [18] two facts supported by visual material should be verified:  
1. the dependence of the biological system reaction on the frequency of alternating the components of a combined magnetic field (CMF); i.e., the most pronounced response of the biosystem is achieved at the CMF tuned to the resonance frequency \(f_{\rm c}\) of the given bound ion, and as the frequency recedes from the \(f_{\rm c}\), the response rate of the biosystem also decreases, Figure 1 (left). 2. dependence of the biological system response on magnetic flux density magnitude ratio \(B_{\rm AC}/B_{\rm DC}\) of CMF, i.e., the most pronounced response of the biosystem appears at a \(B_{\rm AC}/B_{\rm DC}\) ratio of 1.8, and as the ratio recedes from this value, the response rate of the biosystem also decreases, Figure 1 (right). From presented state-of-the-art studies it is clear, that investigations within this scientific area often provide contradictory results. Quite a large number of cited research works suffer from insufficient methodology description leading to the inability of independent replication of experiments and thus lack of reproducible and scientifically acceptable evidence. The complexity of problematics focused on nonthermal biological effects of LF EMF is another strong limitation and a possible reason for the ambiguities even within the experiments focused on physical mechanisms of LF EMF, or more accurately LF MF action on biological objects at the cellular or molecular level. To successfully verify any of the proposed mechanisms a lot of effort should be placed not only on a precise setup and control of input physical quantities, but also on ambient conditions, especially on the temperature stability of the experiment, background field stability, or at least monitoring. On the other hand, the mentioned limitations could be understood as a strong motivational factor, to provide scientifically acceptable and reproducible research, which would be accepted as valid evidence of time-varying LF MF effects on biological samples. Therefore, the presented work is focused on the precise establishment of experiments based on chosen conditions, which are in accordance with the postulates of the IPR model. One aim is to perform frequency sensitivity analysis around the predicted resonant point of Ca\({}^{2+}\) ion at a stabilized ratio of CMF magnetic flux density to verify the relevance of the first condition.