(Inside Science) -- In 2006, North Korea conducted its first ever nuclear bomb test. Despite international condemnation, the nation proceeded to explode four more bombs in the following decade.

A global effort to monitor radioactive particles, known as radionuclides, in the atmosphere is crucial to remotely identify such nuclear explosions, according to Jay Zucca, the principal deputy of the Global Security Directorate at Lawrence Livermore National Laboratory in California. Zucca presented an overview of nuclear explosion detection methods at a meeting of the American Physical Society, held in Washington, D.C. last week.

While seismic sensors can detect the unique waves that man-made explosions send rippling through the Earth, radioactive evidence is ultimately needed to verify a seismic event as a nuclear explosion.

In addition to monitoring nations like North Korea, aBrain 'pacemaker' can boost memory

Well-timed pulses from electrodes implanted in the brain can enhance memory in some people, scientists reported on Thursday, in the most rigorous demonstration to date of how a pacemaker-like approach might help reduce symptoms of dementia, head injuries and other conditions.

The report is the result of decades of work decoding brain signals, helped along in recent years by large department of defence grants intended to develop novel treatments for people with traumatic brain injuries, a signature wound of the Iraq and Afghanistan wars. The research, led by a team at the University of Pennsylvania, is published in the journal Current Biology.

Previous attempts to stimulate human memory with implanted electrodes had produced mixed results: Some experiments seemed to sharpen memory, but others muddled it. The