Knowledge Update

Washington, Dec 1 (IANS) NASA's Cassini spacecraft began a "ring-grazing" mission to study Saturn's rings and moons, media reports said.

According to NASA, the "thrilling" ride marked the first phase of a "dramatic endgame" for the 19-year-old spacecraft and over the next five months, Cassini will circle high over and under the poles of Saturn every seven days for a total of 20 times, Xinhua news agency reported.

"We're calling this phase of the mission Cassini's Ring-Grazing Orbits, because we'll be skimming past the outer edge of the rings," Cassini project scientist at NASA's Jet Propulsion Laboratory (JPL) Linda Spilker said in a statement.

"In addition, we have two instruments that can sample particles and gases as we cross the ring-plane, so in a sense Cassini is also 'grazing' on the rings."

During the first two orbits, the spacecraft will pass directly through an extremely faint ring produced by tiny meteors striking Saturn's two small moons Janus and Epimetheus.

Then, ring crossings in March and April will send the spacecraft through the dusty outer reaches of the F ring, which marks the outer boundary of the planet's main ring system.

Cassini's ring-grazing orbits also offer "unprecedented opportunities to observe the menagerie of small moons", including best-ever looks at the moons Pandora, Atlas, Pan and Daphnis, said NASA.

However, these orbits are merely a prelude to the spacecraft's "Grand Finale phase" that will begin in April 2017, when Cassini is scheduled to fly through the 2,350 km gap between Saturn and its rings.

Finally, the long-lived spacecraft will make a mission-ending plunge into the planet's atmosphere on September 15, 2017.

Launched in 1997, Cassini has been touring the Saturn system since arriving there in 2004. 

During its journey, Cassini has made numerous dramatic discoveries, including a global ocean within Enceladus and liquid methane seas on Titan. But the mission is drawing near its end because the spacecraft is running low on fuel. 

​Sydney, Dec 1 (IANS) Australia welcomed the first day of its summer on Thursday with a surge in the maximum temperatures that are expected to soar past 40 degrees Celsius, reports said.

As sun tilted towards the southern hemisphere heatwave was projected for Queensland and New South Wales states, Xinhua news reported.

Temperatures are expected to soar past 40 degrees Celsius over the next three to five days, nine degrees above the December average.

This has forced authorities to activate a safety plan usually reserved for floods and cyclones due to the high risk of heatstroke.

Australia's weather bureau said heatwaves have taken more lives in the 200 years than any other natural hazard downunder.

"For every 100,000 people exposed to a category five heatwave, you would get at least three fatalities," Risk Frontiers' lead catastrophe loss modeller Thomas Loridan said.

Australia's Bureau of Meteorology have rated the heatwave hitting southeast Queensland and northern New South Wales as "severe to extreme".

Washington, Dec 1 (IANS) NASA scientists are developing artificial intelligence for underwater drones that could be used to understand Earths marine environments as well as track signs of life below the surface of icy oceans believed to exist on Jupiter's moon Europa.

While satellites can study the ocean surface, their signals cannot penetrate the water and therefore robotic submersibles have become critical tools for ocean research. 

"Autonomous drones are important for ocean research, but today's drones don't make decisions on the fly," said Steve Chien, who leads the Artificial Intelligence Group at NASA's Jet Propulsion Laboratory, Pasadena, California. 

"In order to study unpredictable ocean phenomena, we need to develop submersibles that can navigate and make decisions on their own, and in real-time. Doing so would help us understand our own oceans -- and maybe those on other planets," Chien said in a NASA statement.

If confirmed, the oceans on moons like Europa are thought to be some of the most likely places to host life in the outer solar system.

If successful, this project could lead to submersibles that can plot their own course as they go, based on what they detect in the water around them. 

That could change how scientists collect data, while also developing the kind of autonomy needed for planetary exploration, said Andrew Thompson, Assistant Professor at California Institute of Technology (Caltech).

"Our goal is to remove the human effort from the day-to-day piloting of these robots and focus that time on analysing the data collected," Thompson said.

"We want to give these submersibles the freedom and ability to collect useful information without putting a hand in to correct them," Thompson noted.

As part of this research, a team of scientists from NASA and other institutions recently used a fleet of six coordinated drones to study Monterey Bay, California.

The fleet roved for miles seeking out changes in temperature and salinity. To plot their routes, forecasts of these ocean features were sent to the drones from shore.

The drones also sensed how the ocean actively changed around them. 

New York, Dec 1 (IANS) Using data from four different telescopes, a team of astronomers led by an Indian-origin researcher has reported that an asteroid discovered last year is the tiniest known asteroid.

At two meters (six feet) in diameter, the asteroid, named 2015 TC25, is also one of the brightest near-Earth asteroids ever discovered, the researchers said.

"If we can discover and characterise asteroids and meteoroids this small, then we can understand the population of objects from which they originate: large asteroids, which have a much smaller likelihood of impacting Earth," said Vishnu Reddy, Assistant Professor at University of Arizona's Lunar and Planetary Laboratory in the US .

"In the case of 2015 TC25, the likelihood of impacting Earth is fairly small," Reddy, an alumnus of Madurai Kamraj University in Tamil Nadu, said.

Small near-Earth asteroids such as 2015 TC25 are in the same size range as meteorites that fall on Earth. Astronomers discover them frequently, but not very much is known about them as they are difficult to characterise. 

By studying such objects in more detail, astronomers hope to better understand the parent bodies from which these meteorites originate.

Discovered by the University of Arizona's Catalina Sky Survey last October, 2015 TC25 was studied extensively by Earth-based telescopes during a close flyby that saw the micro world sailing past Earth at 128,000 kilometres, a mere third of the distance to the moon.

In a paper published in The Astronomical Journal, Reddy noted that new observations from the NASA Infrared Telescope Facility and Arecibo Planetary Radar showed that the surface of the asteroid is similar to a rare type of highly reflective meteorite called an aubrite. 

Aubrites consist of very bright minerals, mostly silicates, that formed in an oxygen-free, basaltic environment at very high temperatures. Only one out of every 1,000 meteorites that fall on Earth belong to this class.

"This is the first time we have optical, infrared and radar data on such a small asteroid, which is essentially a meteoroid," Reddy said. 

"You can think of it as a meteorite floating in space that hasn't hit the atmosphere and made it to the ground - yet," Reddy noted.

New York, Dec 1 (IANS) Lucy -- the common name accorded to the world-famous fossilised remains of an early human ancestor who lived 3.18 million years ago -- was adept at walking on her two legs as well as climbing trees, researchers have determined.

Evidence preserved in the internal skeletal structure of Lucy, a member of the ancient human species known as Australopithecus afarensis, suggests that she climbed trees, the study said.

Since Lucy's discovery in Ethiopia 42 years ago, paleontologists have debated whether she spent her life walking on the ground or combined walking with frequent tree climbing.

The new analysis, published in the journal PLOS ONE, showed that Lucy's upper limbs were heavily built, similar to tree-climbing chimpanzees, supporting the idea that she often used her arms to pull herself up, most likely onto tree branches. 

"It may seem unique from our perspective that early hominins like Lucy combined walking on the ground on two legs with a significant amount of tree climbing, but Lucy did not know she was unique," said one of the researchers John Kappelman from The University of Texas at Austin in the US.

Researchers also suggested that because her foot was better adapted for bipedal locomotion -- or upright walking -- rather than grasping, Lucy had to rely on upper-body strength when climbing, which resulted in more heavily built upper-limb bones.

"We were able to undertake this study thanks to the relative completeness of Lucy's skeleton," study's lead author Christopher Ruff, Professor at Johns Hopkins University School of Medicine, noted. 

"Our analysis required well-preserved upper and lower limb bones from the same individual, something very rare in the fossil record," Ruff said.

A recent study by Kappelman proposed that Lucy probably died after falling from a tall tree, where she may have been nesting to avoid predators. 

​London, Dec 1 (IANS) Patients whose human immunodeficiency virus (HIV) strains developed a resistance to older generation drugs are also resistant to modern drugs, a new study led by an Indian-origin scientist has found.

Resistance to a drug typically occurs when patients doesn't take their medication regularly enough, and for first-line treatments to work, patients generally need to take their medication 85-90 per cent of the time. 

The findings revealed that HIV can be resistant to many different drugs simultaneously.

In the study, the researchers found that 16 per cent of people who stopped responding to modern first-line treatments had HIV mutations associated with resistance to an older generation of drugs called thymidine analogues.

Among patients with a thymidine analogue mutation, 80 per cent were also resistant to tenofovir -- the main drug in most modern HIV treatment and prevention strategies.

"We were very surprised to see that so many people were resistant to both drugs, as we didn't think this was possible," said lead author Ravi Gupta, Professor at University College London.

Mutations for thymidine analogue resistance were previously thought to be incompatible with mutations for tenofovir resistance, but now HIV can be resistant to both at once, the researchers said, adding "this emphasises the need to check the genetic profile of patient's virus before prescribing first-line treatments, as they may have already developed resistance to other treatments that they did not mention having taken." 

Further, in order to prevent these multi-resistant strains from developing, the researchers asserted that there is a need for cheap, reliable resistance testing kits to help screen for drug resistance before giving treatment.

"However, until such kits are widely available, we could test the amount of virus in the bloodstream before and after giving treatment that could help detect treatment failure earlier and switch patients to second line drugs," Gupta said.

If a patient's virus becomes resistant to first-line drugs, the next stage is the expensive second-line treatment with greater side effects.

For the study, published in The Lancet Infectious Diseases, the team studied 712 HIV patients across the world whose HIV was not controlled by antiretrovirals.

New York, Nov 30 (IANS) To make the most relevant replies appear on the top of a tweet thread, Twitter has added a "reply counter" and a "conversation ranking" to its mobile app.

​Sydney, Nov 30 (IANS) Dreamworld, the popular theme park in Australia's Gold Coast in Queensland, is set to reopen on December 10, six weeks after four people died when a ride crashed.

The park was closed after two women and two men, between the ages of 32 and 42, were killed when its Thunder River Rapids ride malfunctioned on October 25.

Dreamworld CEO Craig Davidson said in a statement on Wednesday that Dreamworld and WhiteWater World would reopen following an "unprecedented multi-level safety review", Xinhua news reported.

An inspection in November resulted in 10 improvement and prohibition notices issued for the theme parks.

However, the Thunder River Rapids ride involved in the fatal accident would be demolished.

Washington, Nov 29 (IANS) The first HIV vaccine efficacy study in seven years has begun in South Africa to test whether a modified vaccine candidate can provide effective protection against the AIDS virus, the US National Institutes of Health said.

The study -- called HVTN 702 -- aims to enroll 5,400 sexually active men and women aged 18 to 35 years, making it the largest and most advanced HIV vaccine clinical trial to take place in South Africa, Xinhua news agency reported.

"If deployed alongside our current armoury of proven HIV prevention tools, a safe and effective vaccine could be the final nail in the coffin for HIV," said Director of the National Institute of Allergy and Infectious Diseases (NIAID), Anthony Fauci in a statement.

The experimental vaccine regimen being tested in HVTN 702 is based on the one investigated in the RV144 clinical trial in Thailand that was found to be 31.2 per cent effective at preventing HIV infection over the 3.5-year follow-up after vaccination.

The new trial, to be conducted at 15 sites across South Africa, where more than 1,000 people become infected with HIV every day, aims to test whether it will provide greater and more sustained protection than the RV144 regimen.

Volunteers will been randomly assigned to receive either the investigational vaccine regimen or a placebo. All participants will receive a total of five injections over one year, and results are expected in late 2020.

"If an HIV vaccine were found to work in South Africa, it could dramatically alter the course of the pandemic," said HVTN 702 Protocol Chair and President of the South African Medical Research Council Glenda Gray.