Traditionally, scientists believed that nicotine inhaled in a puff of cigarette smoke took a mere seven seconds to be taken up by the brain, but new evidence indicates that nicotine takes much longer to reach peak levels in the brains of cigarette smokers, according to a new study in PNAS.

Using PET imaging, Duke investigators found for the first time that cigarette smokers actually experience a steady rise of brain nicotine levels during the course of smoking a whole cigarette.

Natural Killer (NK) cells ensnare dangerous cells, such as tumour cells and those infected with bacteria and viruses that are on the run with a bungee-like nanotube, according to research published this week in PNAS. The study shows that NK cells use this bungee to destroy cells that could otherwise escape them.

Researchers are keen to understand how NK cells work because they help the body to fight infection and stop tumours from growing. It is thought that it may ultimately be possible to design drugs that harness the cells' ability to fight disease.

Wealthy consumers in the United States and Europe need to take the lead in efforts to prevent devastating climate change because they outsource their weather breaking carbon emissions to developing nations, according a new study in PNAS.

Researchers at the Carnegie Institution's Department of Global Ecology write that over a third of carbon dioxide emissions associated with consumption of goods and services in many developed countries are actually emitted outside their borders. Most of these emissions are outsourced to developing countries like China.

 A new study in the Archives of Internal Medicine suggests that adults tend to eat less pizza and drink less soda as the prices of these items increase, and their body weight and overall calorie intake also appear to decrease.

The authors point out that such manipulation of food prices has been the foundation of agricultural and food policy for many years and should also be used as a "a mechanism to promote public health and chronic disease prevention efforts."

In a paper published in the Proceedings of the National Academy of Sciences, researchers from the University of California, San Diego and Harvard say they have provided the first laboratory evidence that cooperative behavior is contagious.

 Researchers showed that when one person gave money to help others in a "public-goods game," where people had the opportunity to cooperate with each other, the recipients were more likely to give their own money away to other people in future games. This created a domino effect in which one person's generosity spread first to three people and then to the nine people that those three people interact with in the future, and then to still other individuals in subsequent waves of the experiment.

 A team of researchers has discovered how to efficiently turn carbon dioxide into carbon monoxide using visible light. The discovery opens the doors for scientists to explore what organism is out there – or could be created – to chemically break down the greenhouse gas into a useful form. The results are reported in the Journal of the American Chemical Society.