The quality of entries in the world's largest open-access online encyclopedia, Wikipedia, depends on how authors collaborate, a study by University of Arizona researchers has found.

The research, they say, is the first to explain why some articles on the site are of much better quality than others.

Wikipedia has an internal quality rating system for entries, with featured articles at the top, followed by A, B, and C-level entries. The team randomly collected 400 articles at each quality level and applied a data provenance model they developed in an earlier paper.

Scientists writing in the Monthly Notices of the Royal Astronomical Society say they have found evidence of a catastrophic event they believe was responsible for halting the birth of stars in SMM J1237+6203, a galaxy in the early Universe.

The researchers observed the massive galaxy as it would have appeared just three billion years after the Big Bang when the Universe was a quarter of its present age.

According to their findings, the galaxy exploded in a series of blasts trillions of times more powerful than any caused by an atomic bomb. The blasts happened every second for millions of years, the scientists said.

A new study published in the British Medical Journal suggests that people in good health are almost twice as likely to be interested in sex compared to those in poor health. Sexual activity has health benefits and is linked to living longer, but the new study investigated how general health impacts the quality of sex.

The study also estimate how many remaining sexually active years healthy men and women have left.

The results revealed that at the age of 30, men have a sexually active life expectancy of nearly 35 years and for women it's almost 31 years. At 55, this figure changes to almost 15 remaining years for men and 10 years for women. This gender difference diminishes for people with a spouse or intimate partner.

Researchers from Kuwait University predict that world conventional crude oil production will peak in 2014 — almost a decade earlier than some other predictions.

The team explains that scientists have developed several models to forecast the point at which oil production reaches a maximum and then declines, and some put the date at 2020 or later. One of the most famous forecast models, called the Hubbert model, accurately predicted that oil production would peak in the United States in 1970.

University of California, San Francisco researchers have uncovered a crucial mechanism that encourages alcohol consumption after extended abstinence.

Previous work has suggested that people, places, and objects associated with alcohol use are potent triggers for eliciting relapse and that cravings for both alcohol and drugs can increase across protracted abstinence. However, the specific molecular mechanisms that underlie pathological alcohol seeking are not well defined.

Some chickens appear to be male on one side of the body and female on the other, and researchers writing in Nature this week say they know why.

It was previously thought that sex chromosomes in birds control whether a testis or ovary forms, with sexual traits then being determined by hormones.

The authors of the new study, however, identified differences between male and female cells that control the development of sexual traits. The scientists have named the phenomenon, cell autonomous sex identity (CASI).

The findings may also be relevant to why males and females differ in behavior and in susceptibility to disease.