Science and Medicine

Great White Shark Bite Explained



The researchers used computer simulations to get a closer look at the feeding behaviors of two shark species—the harmless grey nurse shark (also called the sandtiger) and a sub-adult great white shark.

The great white shark’s flesh-tearing teeth get all the glory for the predator’s ferocity. But new research suggests there’s much more finesse under the hood to explain a shark’s bite.

It turns out the arrangement of their jaw muscles lets great white sharks maintain loads of bite force no matter how wide their mouths are open—mammals, like us, can’t do that.

The study also suggests that only adult great whites can take advantage of this full biting power. While teenage great whites might have the power to chomp down on an adult-size meal, their jaws wouldn’t stand up to the stresses generated.

“This unique jaw muscle arrangement in sharks will open many questions to its role in the feeding behavior of other shark species and how they have evolved a range of successful feeding strategies,” said lead researcher Toni Ferrara, a doctoral student at the University of New South Wales in Australia.

The findings are detailed in the Journal of Biomechanics.

Toothy sharks

Shark biologists typically look at a shark’s teeth to figure out what the predator eats. For instance, “great whites have broad, triangular-shaped teeth that act like a saw, while sandtigers have needle shaped teeth that grab and puncture prey,” Ferrara told LiveScience.

The researchers used computer simulations to get a closer look at the feeding behaviors of two shark species—the harmless grey nurse shark (also called the sandtiger) and a sub-adult great white shark.

Read more: Great White Shark Bite Explained

 

Cloud Study Predicts More Global Warming



This is the type of marine stratus clouds off the South American coast that was studied in the model simulations. (Credit: Image courtesy Cameron McNaughton)

Current state-of-the-art global climate models predict substantial warming in response to increases in greenhouse gases such as carbon dioxide. The models, though, disagree widely in the magnitude of the warming we can expect. The disagreement among models is mainly due to the different representation of clouds. Some models predict that global mean cloud cover will increase in a warmer climate and the increased reflection of solar radiation will limit the predicted global warming. Other models predict reduced cloudiness and magnified warming.

In a paper that has just appeared in the Journal of Climate, researchers from the University of Hawaii Manoa (UHM) have assessed the performance of current global models in simulating clouds and have presented a new approach to determining the expected cloud feedbacks in a warmer climate.

Lead author Axel Lauer at the International Pacific Research Center (IPRC) at UHM notes: “All the global climate models we analyzed have serious deficiencies in simulating the properties of clouds in present-day climate. It is unfortunate that the global models’ greatest weakness may be in the one aspect that is most critical for predicting the magnitude of global warming.”

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Importance of Exercise for Those at Special Risk for Alzheimer’s



In the study groups of those carrying the gene, individuals who exercised showed greater brain activity in memory-related regions than those who were sedentary.

In a study that included healthy 65- to 85-year-olds who carried a high-risk gene for Alzheimer’s disease, those who exercised showed greater brain activity in memory-related regions than those who were sedentary. The results suggest that physical activity promotes changes in the brain that may protect high-risk individuals against cognitive decline.

Physical activity promotes changes in the brain that may protect high-risk individuals against cognitive decline, including development of Alzheimer’s disease, according to a new study done at the University of Wisconsin-Milwaukee (UWM).

J. Carson Smith, an assistant professor of health sciences, included in the study both people who carry a high-risk gene for Alzheimer’s disease, and other healthy older adults without the gene.

“Our study suggests that if you are at genetic risk for Alzheimer’s disease, the benefits of exercise to your brain function might be even greater than for those who do not have that genetic risk,” says Smith.

While evidence already shows that physical activity is associated with maintenance of cognitive function across a life span, most of this research has been done with healthy people, without any consideration of their level of risk for Alzheimer’s, says Smith.

A team of researchers compared brain activation during memory processing in four separate groups of healthy 65- to 85-year-olds. The level of risk was defined by whether an individual carried the apolipoprotein E-epsilon4 (APOE-ϵ4) allele. Physical activity status was defined by how much and how often the participants reported physical activity (PA). The study divided subjects into Low Risk/Low PA, Low Risk/High PA, High Risk/Low PA and High Risk/High PA.

Read more: Importance of Exercise for Those at Special Risk for Alzheimer’s

   

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