Let’s say a college student enters a classroom to take a test. She probably already has an idea how she will do—knowledge available before she actually takes out a pencil. But do animals possess the same ability to think about what they know or don’t know?

A new study by researchers from the University of Georgia, just published in the journal Current Biology, shows that laboratory rats do.

University College London researchers have found the first physiological evidence that invisible subliminal images do attract the brain's attention on a subconscious level. The wider implication for the study, published in Current Biology, is that techniques such as subliminal advertising, now banned in the UK but still legal in the USA, certainly do leave their mark on the brain.

Using fMRI, the study looked at whether an image you aren't aware of ¬– but one that reaches the retina – has an impact on brain activity in the primary visual cortex, part of the occipital lobe. Subjects' brains did respond to the object even when they were not conscious of having seen it.

A protein known as the "master watchman of the genome" for its ability to guard against cancer-causing DNA damage has been found to provide an entirely different level of cancer protection: By prompting the skin to tan in response to ultraviolet light from the sun, it deters the development of melanoma skin cancer, the fastest-increasing form of cancer in the world.

In a study in the March 9 issue of the journal Cell, researchers at Dana-Farber Cancer Institute report that the protein, p53, is not only linked to skin tanning, but also may play a role in people's seemingly universal desire to be in the sun – an activity that, by promoting tanning, can reduce one's risk of melanoma.

Patients admitted to hospitals for ischemic stroke on weekends had a higher risk of dying than patients admitted during the week, in a Canadian study published in Stroke: Journal of the American Heart Association.

A "weekend effect" has been previously documented when looking at other conditions such as cancer and pulmonary embolism; however, little is known of its impact on stroke death.

"What is really novel in our work beyond the discovery of the 'weekend effect' on ischemic stroke is the subgroup analysis in other settings/characteristics and the identification of variables associated with the 'weekend effect,'" said Gustavo Saposnik, M.D., M.Sc., lead author of the study.

Two new studies by University of California, Berkeley, scientists highlight the amazing promiscuity of genes, which appear to shuttle frequently between organisms, especially more primitive organisms, and often in packs.

Such gene flow, dubbed horizontal gene transfer, has been seen frequently in bacteria, allowing pathogenic bacteria, for example, to share genes conferring resistance to a drug. Recently, two different species of plants were shown to share genes as well.

A new understanding of how plants manage their internal calcium levels could potentially lead to genetically engineering plants to avoid damage from acid rain, which robs soil of much of its calcium.

"Our findings should help scientists understand how plant ecosystems respond to soil calcium depletion and design appropriate strategies to protect the environment," said Zhen-Ming Pei, a Duke University assistant professor of biology who led the study, to be published in the Friday, March 9, issue of the journal Science.

The research was supported by the National Science Foundation, the U.S. Department of Agriculture and Xiamen University in China.

Calcium enters plants dissolved within the water that roots take in from surrounding soil.