Mes: mayo 2011

A highly developed sense of smell kick-started the development of mammals’ big brains.

Scientists used very high-resolution scanning to study the skulls of two of the earliest known mammal species.

Comparing the shape of their brain cases to those of slightly earlier animals, or “pre-mammals”, revealed that the first brain areas to over-develop were those associated with the sense of smell.

The findings are published in Science.

An improved sense of smell may have allowed our tiny, furry ancestors to hunt at night.

The researchers were able to create 3D images of prehistoric animals’ brains using the latest computed tomography, or CT, scanning methods.

“The results tell us that dark energy is a cosmological constant, as Einstein proposed. If gravity were the culprit, then we wouldn’t be seeing these constant effects of dark energy throughout time.”

The latest findings have come from a galaxy survey project called WiggleZ, which began in 2006 and finished this year. WiggleZ used data from Nasa’s Galaxy Evolution Explorer (Galex) space telescope and the Anglo-Australian Telescope on Siding Spring Mountain in Australia.

The survey mapped the distribution of galaxies in an unprecedented volume of the Universe, looking eight billion years back in time – more than half the age of the Universe.

Cosmologist Bob Nicholl, who was not involved with the research, told BBC News: “This is a major step forward. These guys are serious, major scientists and we’ve been waiting for this result for some time.

The professor of astrophysics at Portsmouth University, UK, added: “It’s re-confirmation of dark energy, it gives us another data point to fit our theories around and it shows us the way to the future. More astronomers are going to be doing this in years to come.”

While dark energy makes up about 74% of the Universe, dark matter – which does not reflect or emit detectable light – accounts for 22%. Ordinary matter – gas, stars, planets and galaxies – makes up just 4% of the cosmos.

However, despite scientists being able to infer the existence of dark energy and dark matter, these phenomena still elude a full explanation.

“Tardigrades can be found all over the world from the Arctic to the Antarctic, from high mountains to deserts, in urban areas and backyard gardens,” he explained.

“In terrestrial environments, they always require at least a film of water surrounding their bodies to perform activities necessary for life.”

But if these conditions change, tardigrades are capable of entering an extreme form of resting called cryptobiosis.

In this state, they are capable of withstanding freezing, a process called cryobiosis, and desiccation, a process called anhydrobiosis.

Arid state

“This capability [to withstand desiccation] involves a complex array of factors working at molecular, physiological and structural levels,” Professor Guidetti told BBC News.

“The physiology and biochemistry of anhydrobiosis is bound to a complex system that involves many different molecular components working together as bioprotectants.”

Sugars and heat stress proteins, which are expressed when cells become stressed, act as “molecular chaperones” protecting important molecules within the cell.

The disaccharide sugar called trehalose plays a role in the protection of cells and biomolecules from dehydration by replacing water that is normally bonded to hydrogen.

During dehydration, loss of water increases the ionic concentration leading to the formation of reactive oxygen species (ROS) which damage important biomolecules including DNA.

To counter this attack, organisms produce antioxidants that can mop up ROS minimising cell damage.

The regulation of antioxidant metabolism represents a crucial strategy to avoid damage during dehydration.

“Tardigrades can persist for months, or even for years, in the anhydrobiotic state. When in the desiccated state, tardigrades show a high resistance to physical and chemical extremes,” explains Professor Guidetti.

“For example, very low and high temperatures, exposure to high pressure or vacuum, as well as contact with organic solvents and ionising radiation.”

Exposure to the conditions found in space induces rapid changes in living systems.

Reports that the Large Hadron Collider had detected the first possible signs of the elusive Higgs boson particle were “wrong”, experts have said.

Last month, an internal memo outlining a possible signal from the Higgs picked up at the LHC was leaked on to the web.

But cross-checks of the data collected by the Atlas experiment have since found no signal.

The details were revealed during a talk by senior officials at the Royal Society in London.

The Higgs boson is of huge importance to the widely accepted theory of physics, known as the Standard Model.