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See Inside October 2008

Updates: Whatever Happened to LED Lightbulbs?

Also Updates on Bubbles Producing Light, Virus-Infecting Viruses and Galapagos Tortoise Breeding

Bubbly Gone Flat
Water bubbles created by ultrasonic waves can collapse fast enough to generate a flash of light [see “Sonoluminescence: Sound into Light”; SciAm, February 1995]. In 2002 Rusi Taleyarkhan, then at Oak Ridge National Laboratory, claimed to have triggered nuclear fusion in these bubbles; in 2006 he published a second report of successful bubble fusion. In both cases, other researchers could not duplicate his work, and many were suspicious because he did not share his data. Contamination with a radioisotope could also explain his 2006 results.

The tempest over bubble fusion may have finally fizzled out. After their second investigation, officials at Purdue University, Taleyarkhan’s current institution, charged him in July with two counts of misconduct after concluding that he falsely created the appearance that members of his lab had independently verified the sonofusion effect. (An earlier inquiry cleared Taleyarkhan, but lawmakers requested a more thorough investigation into the research, which received $318,000 in government funding.) Taleyarkhan has appealed the charges.

In 2007 Kenneth Suslick of the University of Illinois and Seth Putterman of the University of California, Los Angeles, reconstructed Taleyark­han’s original experiment but found no fusion. At this point, scientists have given up, Suslick says: “These experiments were deeply flawed at best and have had no credibility for several years.”

It’s Alive?
For decades scientists have argued about the life status of viruses [see “Are Viruses Alive?”; SciAm, December 2004]. Researchers at the University of the Mediterranean in Marseille, France, and their colleagues have discovered that viruses can fall ill through infection by other viruses. The finding, published online by Nature August 6, provides an indication that viruses could be considered living.

The researchers looked at the giant mamavirus, which is as large as a small bacterium, about 750 nanometers. Electron microscopy revealed a tiny virus about 50 nanometers across that is closely linked with the mamavirus. Lacking the ability to infect cells, the satellite virus, dubbed Sputnik, relies on mamavirus to do the job. Then Sputnik hijacks the replication factory that mamavirus has set up in the cell. The result is more Sputnik and fewer and often deformed mamavirus. Genome studies suggest giant viruses and their “viro­phages” may be common in the oceans.

Light Work
Light-emitting diodes are making their way into everyday life [see “In Pursuit of the Ultimate Lamp”; SciAm, February 2001]. Still, LED versions of 60-watt incandescent bulbs can cost around $100. Engineers at Purdue University report a way to make cheaper blue LEDs, which are needed to generate white light. Conventionally, such LEDs require gallium nitride to be placed on a substrate of sapphire, with a separate reflector to direct the light. In the July 14 Applied Physics Letters, the researchers describe making LEDs on silicon with a built-in reflective layer, which reduces cost; with mass manufac­turing, affordable LED lamps could appear  in two years, they predict.

Family Guy
Lonesome George, the famous bachelor tortoise of the Galápagos, may soon be a father. The sole survivor of a population on Pinta, a northern island of the Galápagos—pirates and sailors had eaten the rest of his kind—George now lives at the Charles Darwin Research Station on Santa Cruz. In 1990 two females from Isabela Island joined him. Unfortunately, George showed little sexual interest or prowess. In July, however, one female produced nine eggs, three of which were undamaged and collected for incubation. Because turtles can lay unfertilized eggs, no one will know if George has sired offspring until mid-November, when the eggs should hatch if fertile. Success could mean the eventual restoration of the Pinta subspecies [see “On the Origins of Subspecies”; SciAm, March 1999].

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