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How do magnetic fields affect biological tissue? An entire field of science called bioelectromagnetics has grown up to study this problem and yet nobody is quite sure how to answer this question.

It’s possible that several mechanisms may be at work and today Zakirjon Kanokov from the Joint Institute for Nuclear Research in Dubna, Russia, and a few pals suggest a new one. They start by considering the way in which heat jiggles charge carriers in any system above absolute zero. This gives rise to tiny, unpredictable and rapidly varying changes in any current, a phenomenon known as Johnson noise.

Kanokov and co consider the case when the charge carriers are ions in a fluid flowing through a tube. The ions are free to move but obviously confined within a specific volume. The team then poses the question: what happens when you apply a static magnetic field?

The answer, they say, is a resonance effect in which the ionic currents grow stronger. The strength of the resonance depends on the size of the capillary and the strength of the field.

Kanakov and co have worked out how this effect might play out in the human body; after all the body is filled with calcium ions in a fluid flowing through narrow tubes.

They say that this kind of resonance can occur in the aorta at magnetic field strengths of a few picoteslas (10^-12 T) and in narrower capillaries at a few hundred microteslas. The Earth’s field is a few tens of microteslas.

That’s an interesting calculation that will need some careful testing.

The team go further and speculate that these ionic currents may disrupt blood flow and cause tissue damage. That’s a big jump that is not backed up by their calculations but an interesting conjecture nonetheless. But finding this effect against a background of all the other ways in which tissue becomes damage is going to be a devil of a task.

Ref: arxiv.org/abs/0904.1198: On the Influence of Weak Magnetic and Electric Fields on the Fluctuations of Ionic Electric Currents in Blood Circulation

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