Washington, Jan 06: A team of astrophysicists has developed the first complete map of the Milky Way galaxy’s four spiral arms. The new map was developed by Iowa State University’s Martin Pohl, Peter Englmaier of the University of Zurich in Switzerland and Nicolai Bissantz of Ruhr-University in Bochum, Germany.

As the sun and other stars revolve around the center of the Milky Way, researchers cannot see the spiral arms directly, but have to rely on indirect evidence to find them. In the visible light, the Milky Way appears as an irregular, densely populated strip of stars. Dark clouds of dust obscure the galaxy’s central region; so it cannot be observed in visible light.

The National Aeronautics and Space Administration’s Cosmic Background Explorer satellite was able to map the Milky Way in infrared light using an instrument called the Diffuse IR Background Experiment. The infrared light makes the dust clouds almost fully transparent. Englmaier and Bissantz used the infrared data from the satellite to develop a kinematic model of gas flow in the inner galaxy.

Pohl used the model to reconstruct the distribution of molecular gas in the galaxy, and that led to the researchers’ map of the galaxy’s spiral arms. The map shows that the inner part of the Milky Way has two prominent, symmetric spiral arms, which extend into the outer galaxy where they branch into four spiral arms.

“For the first time, these arms are mapped over the entire Milky Way,” said Pohl, an Iowa State associate professor of physics and astronomy. “The branching of two of the arms may explain why previous studies, using mainly the inner or mainly the outer galaxy, have found conflicting numbers of spiral arms,” he added.

In addition to the two main spiral arms in the inner galaxy, two weaker arms exist. These arms end about 10,000 light-years from the galaxy’s center. One of these arms has been known for a long time, but has always been a mystery because of its large deviation from circular motion.

The new model explains the deviation as a result of alternations to its orbit caused by the bar’s gravitational pull. The other, symmetric arm on the far side of the galaxy was recently found in gas data. The discovery of this second arm was a great relief for Englmaier. “Finally, it is clear that our model assumption of symmetry was correct and the inner galaxy is indeed quite symmetric in structure,” he said.

ANI

London, Jan 06: If scientists have their way, future astronauts would be literally going into space by a broomstick, in the form of a 100,000km long tether anchored to the Earth as a “space elevator”.

According to a report, Raymond Riise of the European Space Agency demonstrated the device at a space elevator conference in December last year.

First mooted by Russian scientist Konstantin Tsiolkovsky in 1895, the space elevator idea has captured imaginations as what would be the greatest space mission ever conceived. The idea rests on making use of the outward centrifugal force supplied by the Earth’s rotation.

If the centrifugal force provided by the Earth is balanced with its gravitational force, by making use of a space elevator cable or tether whose centre of mass is at geostationary orbit, the tether would be held taut permanently, providing a means to propel people and cargo into space.

A long-standing critical issue is how to power the “climber” that would ascend the cable into space. Prevailing ideas include delivering microwave or laser power to the climber beamed from the Earth’s surface, or even from orbiting solar power collectors. But, European Space Agency ground station engineer Riise provided a markedly more simple idea. He proposed sending power mechanically, effectively by providing a carefully timed jerk of the cable at its base.

To demonstrate, he employed a broomstick to represent the cable held in tension, and an electric sander to provide a rhythmic vibration to the bottom of the stick.

Around the broomstick’s circumference, he tied three brushes representing the climber with their bristles pointing downwards, meaning it took slightly more force to lower the brush assembly than to raise it.

The vibration from the sander allowed the assembly to slide upward along the broomstick as it moved slightly downward, but grip it as it moved slightly upward. The net effect was that the assembly rose against gravity straight to the top of the stick.

The prototype’s approach would make for a bumpy ride in practice, but according to Riise, the rhythmic tugging on the cable could be smoothed out.

“It would be possible to make a suspension system that completely decouples the cabin where the passengers are,” he told. “For them, it would be a linear movement with very little disturbance,” he added.

ANI

Washington, Jan 5: Researchers led by an Indian American have developed a versatile mouse model of glioblastoma - the commonest of deadly brain cancers in humans.

"Mouse models of human cancer have taught us a great deal about the basic principles of cancer biology," said Inder Verma, professor in the Laboratory of Genetics at the Salk Institute.

"By definition, however, they are just that: approximations that simulate a disease but never fully capture the molecular complexity underlying disease in humans."

Verma received his Ph.D. from the Weizmann Institute of Science and was a postdoctoral fellow at MIT. He is an American Cancer Society professor of molecular biology and recipient of an NIH (National Institutes of Health) Outstanding Investigator award. Verma is the director of the Laboratory of Genetics at the Salk Institute.

Trying to mimic randomly occurring mutations that lie at the heart of all tumours, Salk Institute researchers used modified viruses to shuttle cancer-causing oncogenes into a handful of cells in adult mice.

This could not only prove very useful in faithfully reproducing different types of tumours but also to clarify the nature of elusive cancer stem cells.

The most frequently used mouse cancer model relies on xenografts: Human tumour tissue or cancer cell
lines are transplanted in mice programmed to develop tumours quickly.

"These tumours are very reproducible, but this approach ignores the fact that the immune system can make or break cancer," said co-author Tomotoshi Marumoto, former postdoctoral researcher in the Verma lab and now an assistant professor at the Kobe Medical Centre Hospital in Kobe, Japan.

Other animal models either express oncogenes in a tissue-specific manner or shut down the expression of tumour suppressor genes in the whole tissue.

"But we know that tumours generally develop from a single cell or a small number of cells of a specific cell type, which is one of the major determinants of the characteristics of tumour cells," explained co-author Dinorah Friedmann-Morvinski.

To sidestep the shortcomings of currently used cancer models, the Salk team harnessed the power of lentiviral vectors to infect nondividing as well as dividing cells and ferry activated oncogenes into a small number of cells in adult, fully immunocompetent mice, said a Salk Institute release.

"These findings show that our cancer model will not only allow us to start understanding the biology of glioblastoma but will also allow us to answer many questions surrounding cancer stem cells," said Verma.

Although the work described to date pertains to glioblastoma, Verma and his team are currently using this methodology to investigate lung, pancreatic, and pituitary cancers.

IANS