Purdue University officials today announced that a second and final internal inquiry has cleared bubble-fusion researcher Rusi Taleyarkhan of all allegations of research misconduct. "I feel vindicated and exonerated," Taleyarkhan says. "It's been a pressure cooker for about a year." But controversy surrounding Taleyarkhan's work isn't likely to die down any time soon.
Taleyarkhan is the chief proponent of the controversial notion of sonofusion, which suggests that sound energy can collapse bubbles in a way that yields more energy than was initially put in (ScienceNOW, 4 March 2002). Last year, an article in Nature reported that several of Taleyarkhan's colleagues at Purdue were upset by their encounters with him, suggesting that he allegedly obstructed their work and tried to stop them from publishing results that contradicted his own.
Purdue appointed a committee to review the allegations. In June, the university reported that it had completed an initial inquiry but that the results would not be made public (ScienceNOW, 20 June 2006). Purdue officials say that details of the latest report, the charges, and even the makeup of the committee will also be kept confidential, and that the inquiries are over. "We're done with it," says Purdue University spokesperson Jeanne Norberg.
But other experts both inside and outside the university challenge Purdue's exoneration, arguing that the process was shrouded in so much secrecy that it's impossible to know what the review actually entailed. "It's outrageous. I don't know what Purdue is doing," says Lefteri Tsoukalas, a nuclear engineer at Purdue who initiated some of the allegations against Taleyarkhan. Tsoukalas said he spoke to the original review committee last spring and was asked to resubmit written allegations in September. Yet, Tsoukalas says, neither he nor anyone else he knows who has been involved in the case was ever interviewed by the latest panel. Seth Putterman, who headed a DARPA-funded effort to replicate Taleyarkhan's work, says that he too was never contacted by the panel and is frustrated by the ongoing secrecy. "How do I respond to a secret investigation by a secret internal panel?" he asks.
One way Putterman and his colleagues have responded is in the literature. In Friday's issue of Physical Review Letters, Putterman and Kenneth Suslick at the University of Illinois report that they reproduced Taleyarkhan's original sonofusion setup but that it didn't work. The experiment is designed to use ultrasound to collapse bubbles and force deuterium atoms to fuse, liberating either tritium and a proton or helium-3 and an extra neutron. Suslick says their experiment detected only 0.01% of the excess neutrons Taleyarkhan claims to have observed. Although a negative result, it ensures that the high temperatures generated by sonofusion aren't likely to cool off any time soon.