Ozone Recovery, Warmer Antarctica
The Antarctic ozone hole that forms every spring has kept that continent's interior cold even as the rest of the world has warmed over the past few decades [see "A Push from Above"; SciAm, August 2002]. Thanks to the global ban on chlorofluorocarbons, stratospheric ozone levels there are slowly recovering. A repaired hole, however, could speed Antarctic ice melting and change weather patterns, according to a computer model by Judith Perlwitz of the University of Colorado at Boulder and her colleagues. With more ozone, the lower stratosphere would absorb more ultraviolet light and warm up by as much as nine degrees Celsius. That in turn would break down circulation patterns that trap cold air over Antarctica's interior, making the continent heat up. The changed patterns would also make Australia warmer and drier, and South America could get wetter. Such ozone details may need to be worked into global climate models, most of which have neither incorporated such effects nor included enough of the stratosphere. The journal Geophysical Research Letters published the study on April 26.

Protecting Cells From Radiation
Scientists remain on the lookout for novel drugs that combat radiation damage. One of the most promising is CBLB 502, made by Cleveland Biolabs in Buffalo, N.Y.  [see "Surviving Side Effects"; SciAm, October 2007]. In the April 11 Science, researchers report that the drug, also called Protectan, enabled 87 percent of mice to survive lethal doses of radiation, although it worked only if injected within an hour before exposure. (It showed some protective effects if injected after exposure to lower levels of radiation.) The compound, which could be given in the event of a nuclear explosion or meltdown, did not shield malignant cells, so it could protect healthy cells of cancer patients undergoing radiation treatment. The company now needs to test the agent in large numbers of people. —David Biello

Quantum Side Step
In 1879 Edwin Hall discovered that a magnet can deflect the flow of electrons, like wind pushing ships off course. In 1980 physicists observed the quantum version, in which the applied magnetic field pushes electrons in discrete steps; it is as if the ships were responding to separate gusts even though a steady wind was blowing [see "Electrons in Flatland"; SciAm, March 1996].

Now Princeton University physicists have demonstrated the quantum Hall effect without any applied magnetic field. They created special conditions for electrons in a bismuth crystal such that when the electrons travel close to the speed of light, they effectively generate their own magnetic field that deflects them. Such unusual materials not only elucidate the fundamental nature of the quantum Hall effect—it is deeply connected to superconductivity—but also could lead to novel electronic technology. The work appears in the April 24 Nature.

Difference Engine No. 2—No. 2
Nineteenth-century British mathematician and engineer Charles Babbage has a host of inventions to his name, including the standard railroad gauge, the cowcatcher and the ophthalmoscope. A famous design he never built is his Difference Engine No. 2, a piece of Victorian technology meant to tussle with logarithms and trigonometry. Working from Babbage’s 1849 plans, Doron D. Swade, a curator at London’s Science Museum, constructed the first working version of it in 1991 [see “Redeeming Charles Babbage’s Mechanical Computer”; SciAm, February 1993], which is on display at the museum. Now Swade has constructed a second engine, unveiled on May 10 for a one-year exhibition at the Computer History Museum in Mountain View, Calif. It consists of 8,000 bronze, cast-iron and steel parts, weighs five tons and measures 11 feet (3.4 meters) long and seven feet (2.1 meters) high. —Larry Greenemeier

Note: This story was originally printed with the title: "Updates: Whatever Happened To...?".