North Korea says it's pulling out of disarmament talks and restarting its nuclear reactor, after its launch of a rocket that critics said was designed to test its long-range missile technology drew international outrage.

North Korea claimed it successfully launched the rocket on April 5, carrying a satellite into orbit for the purpose of exploring space. But the North American Aerospace Defense Command (NORAD) said it had launched a missile whose top stages and payload landed in the Pacific Ocean. The U.N. Security Council condemned the launch yesterday, prompting North Korea's declaration today. Over the course of six years, the country has participated in talks (stalled since last year) with five countries — the U.S., China, South Korea, Japan and Russia. The negotiations have led the country to disable some of its main nuclear reactor and to disclose some of its weapons program in exchange for fuel and food.

It's a busy time for nuclear-policy analysts: Just days after President Obama told a crowd of 20,000 in Prague that the U.S. had a “moral responsibility" to take the lead in ridding the world of nuclear weapons, two groups have come forward with their own blueprints for doing so.

A report from one group, instead of endorsing Obama’s first priority, the U.S. ratification of the Comprehensive Test Ban Treaty (CTBT), advocates a radical rethinking of American nuclear weapons policy. The other report recommends reducing the number of warheads in the U.S. nuclear arsenal to 500, down from today’s total of around 5,000.

Both reports come just days before a Congressionally mandated Commission on the Strategic Posture of the United States is scheduled to release a review of “nuclear weapons policy, strategy, and force structure.”

Even though heart attacks may not be deadly, they can leave your ticker damaged. The reason: they occur when blood flow to a section of heart muscle becomes blocked. If the flow of blood isn't restored quickly, a section of the heart muscle becomes damaged from the lack of oxygen and begins to die, weakening its ability to pump blood.

Researchers have long wondered whether such damage could be reversed, that is, whether hobbled heart muscle cells could regenerate — potentially affecting the ability of scientists to hatch ways to repopulate damaged heart tissue. A study in Science today confirms that some heart muscle cells do, in fact, regenerate slowly over the course of a person's lifetime. Scientists from the Karolinska Institute in Sweden report that in early adulthood, we're continually renewing about 1 percent of our heart cells a year; that regeneration slows down, but it still occurs in old age, with a little less than half of 1 percent of cells regenerating at age 75. All told, we've renewed about 40 percent of our heart cells by age 70, neuroscientist Jonas Frisén told Science in a podcast.

France has established a $13.5 million (10 million euro) fund to compensate people who claimed they became sick as a result of its four decades of nuclear testing in Algeria and French Polynesia, government officials announced yesterday.

Some 150,000 people were "theoretically" exposed to radiation from the more than 200 tests conducted between 1960 and 1996, French Defense Minister Herve Morin told the French newspaper Le Figaro, according to the New York Times. Until now, France has denied the radiation released had caused a host of ills, including cancer, in residents in neighboring communities and workers who conducted the tests.

'Tis the season to get rid of nukes? In an effort to achieve world peace and lessen the growing threat of nuclear power, a nascent group including the likes of former President Jimmy Carter, former Soviet leader Mikhail Gorbachev, Bishop Desmond Tutu and Arab League Secretary General Amr Moussa this week launched a campaign calling for the elimination of nuclear weapons.

The new organization, Global Zero, is planning a grassroots effort to spur world powers to rid the planet of nukes over the next 25 years. Meeting yesterday and Monday in Paris, 100 past and current world leaders signed a declaration imploring the U.S. and Russia to slash their nuclear arsenals and for a system to be created to verify that countries are complying with non-proliferation treaties, according to the Associated Press.

If you thought the Cold War was over—that long nuclear standoff that shaped the last five decades of the 20th century—think again. Following his American counterpart, and perhaps prompted by new tensions over the war in Georgia and the agreement between the U.S. and Poland to deploy a missile defense system there, Russian president Dmitry Medvedev has announced plans to upgrade that country's "nuclear deterrent" by 2020.

It's part of a full upgrade for the Russian armed forces: more nuclear-powered subs, better bombs as well as their own "air and space defense network". "Star wars" has at last come to a galaxy not so far away.

The move prompted U.S. Secretary of State Condoleeza Rice to boast that the U.S. possesses an "extremely capable, robust, broad and indeed varied nuclear deterrent," according to an interview with Reuters. That no doubt includes not only the hit-or-miss missile defense effort but also plans to build new nuclear weapons and the industrial complex that develops and fabricates them.