Monday, September 6, 2010

UF STUDY SHOWS CARNIVORE SPECIES SHRANK DURING GLOBAL WARMING EVENT

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A new University of Florida study indicates extinct carnivorous mammals shrank in size during a global warming event that occurred 55 million years ago.

The study, scheduled to appear in the December print edition of the Journal of Mammalian Evolution and now available online, describes a new species that evolved to half the size of its ancestors during this period of global warming.

The hyena-like animal, Palaeonictis wingi, evolved from the size of a bear to the size of a coyote during a 200,000-year period when Earth’s average temperature increased about 15 degrees Fahrenheit. Following this global warming event, Earth’s temperature cooled and the animal evolved to a larger size.

“We know that plant-eating mammals got smaller during the earliest Eocene when global warming occurred, possibly associated with elevated levels of carbon dioxide,” said lead author Stephen Chester, a Yale University doctoral student who began the research at UF with Jonathan Bloch, curator of vertebrate paleontology at the Florida Museum of Natural History. “Surprisingly, this study shows that the same thing happened in some carnivores, suggesting that other factors may have played a critical role in their evolution.”

Researchers discovered a nearly complete jaw from the animal in Wyoming’s Big Horn Basin in 2006 during a fossil-collecting expedition, led by Bloch, a co-author on the study. Bloch said the new findings could help scientists better understand the impact of current global warming.

“Documenting the impact of global climate change in the past is one of the only real experiments that can inform us about what the effects global warming might have on mammals in the near future,” said Bloch, who has studied this climate change event for nearly a decade.

Scientists think the Earth experienced increased levels of carbon dioxide and a drier environment during the warmer time period, but they do not completely understand what caused mammals to shrink.

One theory is that carbon dioxide levels reduced plant nutrients, causing herbivorous mammals to shrink. The newly described species primarily consumed meat, meaning plant nutrients couldn’t have been the only factor, Bloch said.

Mammals in warmer climates today tend to be smaller than mammals in colder climates, Chester said. For example, brown bears in Montana are generally smaller than those found in Alaska.

The study’s other authors are Ross Secord, assistant professor at the University of Nebraska, and Doug Boyer, assistant professor at Brooklyn College.

Bloch said a tooth from this animal was described in a paper about 20 years ago, but scientists did not have enough information to name the new species until finding the jaw.

The species was named after Scott Wing, a paleobotanist at the Smithsonian National Museum of Natural History. He studies the impact the global warming event had on forests in the past, and has played an important role in the collaborative research in the Big Horn Basin, Bloch said.

(Photo: Jennifer Duerden/University of Florida)

University of Florida

HALF-A-LOAF METHOD CAN IMPROVE MAGNETIC MEMORIES

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Chinese scientists have shown that magnetic memory, logic and sensor cells can be made faster and more energy efficient by using an electric, not magnetic, field to flip the magnetization of the sensing layer only about halfway, rather than completely to the opposite direction. They describe the new cell design in the Journal of Applied Physics, which is published by the American Institute of Physics (AIP).

Magnetic random access memory (or MRAM) cells have long been investigated as possible replacements for parts of hard disk drives, flash memory and even computing circuits. Previous designs, however, have proven to be too power-hungry or expensive to be competitive.

"Our new cell design offers a great possibility for data storage elements and logic gates that are fast and non-volatile with ultra-low power consumption," said Dr. Ce-Wen Nan of Tsinghua University in Beijing, China. The new cell is also simpler to make than existing components. Only two layers are needed, compared with three or more for traditional magnetic memories.

The design by Nan's group is a simple thin-layer sandwich of two different materials, each of which has very different magnetic and electrical properties. Applying a voltage to the ferroelectric layer switches its polarization in a way that starts to change the magnetic orientation of the adjacent ferromagnetic layer. This partial change alters the electrical resistance of the entire stack enough to indicate whether the cell is storing a "0" or a "1" data bit. Future research is aimed at understanding and optimizing the materials to increase the resistance change, which will enhance its commercial prospects.

American Institute of Physics

A MOMENT ON THE LIPS, A YEAR ON THE HIPS

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A short period of excess food consumption can have long term effects on your body weight and fat storage even after the initial weight is lost. A study published in BioMed Central's open access journal Nutrition & Metabolism has found that a four-week episode of increased energy intake and decreased exercise can cause increased weight and fat mass more than two years later when compared to control individuals.

Åsa Ernersson worked with a team of researchers from Linköping University Sweden to investigate the long term effects of a sedentary and gluttonous lifestyle. They capped the physical activity of 18 individuals and used excessive food consumption to increase their energy intake by an average of 70% for four weeks. A separate control group ate and exercised as normal.

The intervention group gained an average of 6.4 kg in body weight, which was mostly lost 6 months later. However, one year later the intervention group showed an increased fat mass compared to baseline; the differences were even greater after two and a half years. Ernersson said "The long term difference in body weight in the intervention and control groups suggests that there is an extended effect on fat mass after a short period of large food consumption and minimal exercise."

The study provides interesting new evidence to suggest that even a short period of excessive eating and a lack of exercise can potentially change an individual's physiology, causing it to be harder to lose and keep off weight. Ernersson summarised, "The change of fat mass was larger than expected when compared to the controls, it suggests that even short-term behavioural changes may have prolonged effects on health."

BioMed Central

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