Heat kept plant-eating dinos out of tropics

A hot and dry climate with temperatures exceeding 300 deg C was what kept grass-eating dinosaurs out of the tropics for 30 million years after they first appeared on the planet.

So say scientists in New Mexico who worked with rocks from over 200 million years ago to re-create the climate from that time - the Late Triassic Period.

Despite climatic variations, it was usually too hot for plants and large grass-eating dinosaurs to survive, they found.

The study sheds light on why long-necked dinosaurs seemed to avoid the tropics - many lived north or south of the equator. Fossils of meat-eating dinosaurs, however, can be found there.

"The scientists have developed a new explanation for the perplexing near-absence of dinosaurs in late Triassic equatorial settings," said Dr Rich Lane, the programme director at the earth sciences division of the National Science Foundation, which funded the research.

"That includes rapid vegetation changes related to climate fluctuations between arid and moist climates, and the resulting extensive wildfires."

Atmospheric carbon dioxide levels at the time were four to six times what they are now.

"Our data suggests it was not a fun place," study co-author Randall Irmis of the University of Utah said in a statement.

"It was a time of climate extremes that went back and forth unpredictably. Large, warm-blooded dinosaurian herbivores weren't able to exist near the equator - there was not enough dependable plant food."

The international team of researchers led by geochemist Jessica Whiteside had their findings published in the journal Proceedings of the National Academy of Sciences.

AFP

Breast cancer linked to foetal DDT exposure

A five-decade study of women in the United States has found that those exposed to high levels of DDT pesticide in the womb were four times as likely to get breast cancer.

The study is the first of its kind to directly link breast cancer in humans to DDT, which has been banned in many countries but continues to be used widely in Africa and Asia.

"Environmental chemicals have long been suspected causes of breast cancer but, until now, there have been few human studies to support this idea," said Dr Barbara Cohn of the Public Health Institute in Berkeley, California. She co-authored the study published in the Journal of Clinical Endocrinology and Metabolism.

"This 54-year study is the first to provide direct evidence that chemical exposures for pregnant women might have lifelong consequences for their daughters' breast cancer risk."

Researchers examined women exposed in utero (before they were born) to DDT in the 1960s, when it was heavily used in the US. They focused on 118 women who had daughters diagnosed with breast cancer by the age of 52.

"Independent of the mother's history of breast cancer, elevated levels of DDT in the mother's blood were associated with a nearly four-fold increase in the daughter's risk of breast cancer," said the study.

The chemicals in DDT are known to be endocrine disruptors, which can mimic and interfere with the function of the hormone oestrogen.

AFP

A*Star to showcase 'everyday' science

The Agency for Science, Technology and Research (A*Star) has launched an info-documentary series to showcase the impact of research and development in Singapore and beyond.

Called A*Star TV, the videos will be released online every three to four weeks on YouTube.

The first episode features an automated device called the Sound Eye, which can sense the movements of the elderly without intruding on their privacy.

It helps families check whether elderly family members are safe at home. For instance, it can detect a fall by using ultrasonic and thermal infrared sensors to monitor movements remotely.

In the coming weeks, A*Star will also feature research by local scientist Christine Cheung, to show how better cultivation of brain cells can help improve the understanding of Alzheimer's disease.

"A*Star sees the need to create more awareness among the general public about how science contributes to their everyday lives, and to encourage interest in science, technology, engineering and mathematics education," said an A*Star spokesman.

"We aim to present science and scientific jargon in simpler ways that would resonate with the man in the street."

Compiled by Carolyn Khew