Sir

As chair of the American Physical Society's Committee on International Freedom of Scientists, I wish to express my alarm about the kafkaesque situation confronting the Russian biologist Oleg Mediannikov, reported in your News story 'Russian scientists see red over clampdown' (Nature 449, 122–123; 2007).

The American Physical Society is the biggest organization of physicists in the United States, with a large international membership. The society is independent of any government, and its international freedom committee is responsible for monitoring the human rights of scientists throughout the world, including the United States, and assisting those in need. In the past couple of years our efforts have been partially focused on Russia, where several scientists collaborating with foreign researchers have been intimidated and prosecuted.

As well as Mediannikov, we are actively assisting Valentin Danilov, Oscar Kaibyshev, Igor Sutyagin and Oleg Korobeinichev. We are committed to defending our colleagues at risk and we will continue to raise our voices whenever scholars encounter a prohibition on travelling, publishing or pursuing research. We call upon scientific human-rights organizations to join us to protest at restrictions, by any government, on the free exchange of ideas, be it by denying visas or barring scholars from attending conferences or taking academic positions.