arXiv subjects

Vladimir N. Binhi

Publications and source records attributed to Vladimir N. Binhi.

4 recordsLinked to original sources

arXiv2025

Decoupling spin relaxation and chemical kinetics in radical pair magnetism: A master equation study

A leading theory for the biological effects of low-intensity magnetic fields is the spin-chemical Radical Pair Mechanism. This mechanism is best described by the master equation for the density matrix of an open quantum system, which includes terms for Hamiltonian evolution, thermal spin relaxation, and chemical kinetics. In this study, we have found a solution to this equation for a simplified radical pair model and shown that a significant magnetic effect occurs when the following condition is met: $γH τ\gtrsim 1 + κτ$, where $γ$ is the gyromagnetic ratio of the electron, $H$ is the magnetic field strength, $τ$ is the relaxation time, and $κ$ is the rate of chemical kinetics.

physics.bio-ph↗

arXiv2018

Nonspecific biological effects of weak magnetic fields depend on molecular rotations

The radical pair mechanism is a leading hypothesis in animal magnetic navigation. This mechanism associates the magnetic sense with the visual system, the radical pairs in cryptochromes of the eye retina being specialized magnetic receptors that modulate rhodopsin-mediated photoreception. There are also nonspecific magnetic effects in biology, which occur mostly by chance and originate from the interaction of weak magnetic fields with the magnetic moments dispersed all over the organism at the microscopic level. The radical pair mechanism cannot explain this type of response for many reasons. We have previously shown that the above interaction has a finite probability of resulting in an observable. Here, we develop our physical model of nonspecific magnetic effects for the case of magnetic moments located in rotating molecules. We generalize the results of recent experiments on gene expression in plants in a constant magnetic field, and show that the precession of the magnetic moments that reside on rotating molecules can be slowed relative to the immediate biophysical structures. In quantum mechanical language, the crossing of the quantum levels of magnetic moments conjointly with molecular rotations explain nonspecific magnetic effects and leads to magnetic field-dependences that are in good agreement with the experiment.

physics.bio-ph↗

arXiv2017

Restrictions on the dynamic growth of navigation accuracy in groups of animals

Many migratory animals regularly travel thousands of kilometers, exactly finding their destinations. It is assumed that migrants have both a compass sense to hold their course, and a map sense --- a kind of "biological" GPS --- to correct accumulated errors and determine right direction during navigation. Unlike the compass sense, the map sense is still not reliably explained. Therefore, an alternative way is discussed in literature to eliminate the errors --- the aggregation of animals in groups and their coordinated movement. Orientation accuracy of a group may be significantly higher because the errors caused by the action of a variety of casual factors are averaged. This idea, called the "many wrongs principle," has been confirmed both in behavioral experiments and in the results of computer simulations. However, until now there was no analytical model that considered this effect and its limitations. Such a model is presented in this article. The model is given in terms of the course deviation angle and its variance. It includes a few parameters: individual sensitivity of the animal compass, the power of the herd instinct, and the level of random noise. These parameters determine, among other factors, the size of the group that is optimal for precise navigation. It is shown that there is a range of the noise level, at which the aggregation of individuals into groups that do not exceed a certain size would be favorable.

physics.bio-ph↗

arXiv2013

Effect of the hypomagnetic field on the size of the eye pupil

Previously, we reported that the hypomagnetic field obtained by the 100-fold deprivation of the geomagnetic field affected human cognitive processes as estimated in several computer tests. The exposure to the hypomagnetic field caused a statistically significant increase both in the task processing time and in the number of errors. The magnitude of this magnetic effect, averaged over 40 healthy subjects and more than 10^5 separate trials, was about 1.7%. In the present work, the results of a simultaneous study are described, in which the right eye of each subject was video recorded, while the subject performed the tasks. It has appeared that the pupil size grows in the hypomagnetic field. This effect has been calculated based on the treatment of a large data set of about 6.10^6 video frames. Averaged all over the frames, the magnetic effect on the pupil area was about 1.6%, with high statistical confidence. This is the first laboratory study in which the number of separate trials has been large enough to obtain rather smooth distribution functions. Thus, the small effect of the hypomagnetic field on humans has become evident and statistically valid.

physics.bio-ph↗