A colleague of mine was depressed to find, in a reasonably high impact journal, a statement that magnetic nanoparticles obey Coulomb's law, and thus can be manipulated by external magnetic fields. As far as physics goes, this is just wrong. Coulomb's law is the mathematical relationship that says that the force between two charges is proportional to the product of their charges and inversely proportional to the distance between them. This has nothing to do with magnetic nanoparticles.
I was curious - where did this weird, incorrect statement come from? I turned to google to find out. The earliest result I can find is from this paper by Pankhurst, Connolly, Jones, and Dobson. The paper seems quite good, and the (strange to me) Coulomb's Law language appears to be some shorthand for a physically sound description of the interactions of magnetic materials with magnetic fields. The Pankhurst paper includes the following sentence: "Second, the nanoparticles are magnetic, which means that they obey Coulomb’s law, and can be manipulated by an external magnetic field gradient." This is part of a paragraph that lists three virtues of magnetic nanoparticles for biological applications.
For fun, try copy/pasting that sentence into google. Look at how many times that sentence (indeed, that whole introductory paragraph with very minimal changes) shows up nearly verbatim in other publications. At the risk of saying something actionable, this is plagiarism. This tends to happen in obscure proceedings, edited book chapters, etc., rather than high impact literature. The proliferation of shady publication houses and vanity press journals only aggravates this situation. Very depressing.
Top hit now: an obscure blog called "nanoscale views." Of course yours has proper attribution.
ReplyDeleteThe physics in the Pankhurst et al. paper is correct, but the use of 'Coulomb's Law' for the interaction of magnetic moments with magnetic field gradients is strange indeed. Can't figure out where that could have come from.
ReplyDeleteThe bad physicist - Quentin Pankhurst - responds: Thank you Douglas for pointing this out - it is clearly a mistake that I am sorry to say managed to get through the reviewing and proof checking, and wasn't spotted until you pointed it out just now .. mea culpa. My intent was to refer to a 'magnetic analogue', but somehow it was garbled. The sentence is best understood by just deleting the reference to Coulomb’s law. Sorry for the confusion. Sorry too to learn that the error has been propagating - that's strange indeed, given the basic absurdity of the text.
ReplyDeleteHello Quentin - thanks very much for posting! I'm sorry if my wording sounded overly critical - like I said, I like the paper (and I'm clearly not alone, given how many citations it's received). Yeah, I figured that you were alluding to the analogy (modeling magnetic dipoles like fictitious magnetic charges, etc., as is often done for some magnetostatics calculations). It does make you wonder how many of the people from the chem side get the physics, though, and the bizarre propagation is a symptom of an illness within the publishing culture.
ReplyDeleteNo problem - I'd much rather that the paper was read and questioned, than just cited. Actually, quite a few people have told me that they have used it as a sort of reference text, so I'd be more worried if there were errors in the substantive parts of the paper. Do please let me know if you spot anything.
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