Features

Technology designed by scientists at Oxford University and Leeds University can learn British Sign Language (BSL) signs from overnight TV broadcasts by matching subtitled words to the hand movements of an on-screen interpreter.

The work [detailed here] is a crucial step towards a system that can automatically recognise BSL signs and translate them into words.

A major challenge in recognising signs is to track the signer’s hands as they move on the broadcast – no mean feat as these can get lost in the background, blur or cross – and the arms can assume a vast number of configurations.

The system tackles this problem by overlaying a model of the upper body onto the video frames of the signer by looking for probable configurations, finding the large number of frames where these can be correctly identified and then ‘filling in the gaps’ to infer how the hands get from one position to another.

Another big challenge is to match a target word that appears in a subtitle to the corresponding sign – particularly difficult as words and signs often appear separated in time and words can be signed in many different ways so the corresponding sign may not appear at all.

To overcome this problem the system compares a small number of sequences in which the target word appears in the subtitles with a large number of sequences in which it does not.

Within this footage it then finds the 7-13 frames that appear often in the ‘target word’ sequences and infrequently in the ‘no target word’ ones. This enables it to learn to match over 100 target words to signs automatically.

'This is the first time that a computer system has been able to learn signs on its own and on this scale in this way - with just the information available in the broadcast’s subtitle information and video frames and without the need for humans to give it annotated examples of what each sign looks like,’ said Andrew Zisserman of Oxford University’s Department of Engineering Science who led the work with Patrick Buehler at Oxford and Mark Everingham of Leeds University’s School of Computing.

Mark Everingham said: ‘It demonstrates the sort of very tough problems which advanced image recognition technology is starting to be able to solve. These technologies have the potential to revolutionise the automated searching, classifying and analysis of moving and still images.’

This research was supported by the Engineering and Physical Sciences Research Council, Microsoft and the Royal Academy of Engineering. 

Supershear earthquakes, as this New Scientist feature explains, are the seismic equivalent of a sonic boom.

In these potentially very destructive quakes the rupture travels so fast that it overtakes its own shock waves.

The article highlights the work of David Robinson and Shamita Das from Oxford University's Department of Earth Sciences who are trying to predict where these super-fast quakes are likely to strike next.

They compared past supershears looking for similarities and then looked for faults with the same characteristics: land-based faults that don't deviate by more than 5 degrees over a distance of 100 kms.

What they found were 26 sections on 11 different fault systems around the world that the researchers dubbed 'earthquake superhighways'.

What's especially worrying is that seven sections of superhighway run through highly populated areas - including along the San Andreas Fault under San Francisco and near Rangoon and Mandalay in Burma - with millions of people potentially in danger. 'The density of population in some areas of Asia we looked at is incredibly high. That really surprised me,' David told NS's Richard Fisher.

But as the article explains we just don't know enough about supershear earthquakes yet to advise engineers and planners what to do about them.

We just have to hope that the next one strikes in some remote and uninhabited area giving scientists vital data about these potentially devastating quakes.

Who really invented the wonder drug penicillin?

Alexander Fleming is the name in our history books but tonight a new BBC drama highlights the role Oxford University scientists played in this vital medical breakthrough.

Breaking the Mould: The Story of Penicillin, which airs on BBC Four tonight at 9pm, tells the story of the team which turned Fleming's discovery, that the mould Penicillium notatum produced a substance that inhibited the growth of some bacteria, into the drug that transformed medicine.

According to the Oxford Dictionary of National Biography: 'Alexander Fleming had ‘discovered’ penicillin, essentially by accident, in 1928, but he and his colleagues found that the culture extract containing penicillin was unstable and the antibiotic was impossible to isolate in a pure state, and so they effectively gave up research on it.'

The Oxford scientists Howard Florey and Ernst Chain were key members of the team which began comprehensive experiments with Fleming's mould in 1939, soon after drafting in their colleague Norman Heatley to help solve many of the problems involved in turning out a useful product.

Florey's successor as Head of the Dunn School of Pathology at Oxford, Sir Henry Harris, has written an excellent summary of how the drug was developed and the many scientists who contributed.

In it he highlights the 'forgotten man' of the Oxford group, Norman Heatley, who controversially did not share the 1945 Nobel Prize for the discovery with Fleming, Florey and Chain, writing:

'Heatley's contributions were critical. He first devised the cylinder-plate diffusion technique that provided a reliable and sensitive assay for penicillin and that was later adopted as the standard assay for antibiotic activity.'

'He then suggested a procedure for extracting from organic solvents, in which penicillin was soluble, a stable salt that was soluble in water. This procedure formed the basis of an early counter-current distribution apparatus which Heatley devised and built.'

In advance of the programme being shown Norman Heatley's widow Mercy told the Oxford Mail:

'My husband was particularly good at extracting it [penicillin] from things - I think it seemed to grow best on grapefruit... I feel sad Fleming is always named as the discoverer. I think what happened was he was always happy to talk to the press, whereas Florey wasn’t keen to talk to them and have his team disrupted, which is why Fleming received all the publicity.'

Hopefully the programme will help to set the record straight about who really deserves credit for a drug that's saved so many lives.

Breaking the Mould: The Story of Penicillin will be broadcast on BBC Four on 29 July at 9pm 

Like the Mitchells in Eastenders, nothing is more important than family for elephants.

Elephants maintain a complex social structure but herds are typically all made up of relatives, from travelling packs of mothers and calves to larger groups that contain aunts and cousins.

New research, published in the Proceedings of the Royal Society B and involving Department of Zoology researchers, has looked at what happens to these family groups when elephant populations are drastically affected by poaching. The researchers studied 900 elephants in the Samburu game reserve in northern Kenya over a five year period.

It turns out that viable social groups are so important that elephants will sometimes bring in unrelated animals into the group.

‘Elephants have historically lived in separate herds and do not mix with others that have no genetic link to them – but for the first time different herds have been seen to be joining together,’ writes Richard Alleyne in the Telegraph.

Iain Douglas-Hamilton of the Department of Zoology and founder of the Kenyan-based charity Save the Elephants took part in this research and sends these fantastic images.

‘This paper builds on the work Save the Elephants has been doing on the social structure of elephants in Samburu, but for the first time brings in genetic evidence to define the extent to which spatial associations of elephants have an underlying genetic basis,’ he told Oxford Science Blog.

ScienceNow, Science magazine’s online news site, helpfully explains how: ‘[The research team] pinpointed the elephants' genetic relationships to each other by sequencing DNA from fresh dung samples.’ 

The Samburu elephant population is thought to have lost three-quarters of its members to ivory poachers in the 1970s. As a result, elephants may be willing to accept non-relatives into their social group to ensure they have the critical mass needed to gather food and protect themselves, the researchers suggest.

‘Among the Samburu elephants, the genetic underpinnings have been eroded by high degrees of illegal killing,’ says lead author, George Wittemyer of Colorado State University. ‘Despite this human-driven pruning of their social tree, these elephants formed novel bonds with non-relatives to rebuild the nested structure of their social relations.’ 

Male red jungle fowl can adjust the quality of sperm they produce, depending on how attractive the female fowl is.

The story, reported last week by Discovery Channel online, goes on to explain that males of many promiscuous species in the animal kingdom – including humans – can mate with many females, but they adjust the quality of their sperm to improve chances of fertilization when the female is more attractive.

The Oxford University research published in Proceedings of the Royal Society B involved red jungle fowl, the ancestor of all modern chicken breeds. The team showed that males transfer seminal fluid to matings with attractive females that boosts sperm swimming velocity.

The results provide crucial evidence of what causes variation in sperm quality, which has important implications for fertility and the evolution of sexual strategies.

I caught up with Dr Charlie Cornwallis of the Edward Grey Institute in the Department of Zoology to learn more.

OxSciBlog: Why might cockerels adjust the quality of their sperm when mating with different females?
Charlie Cornwallis: Females vary in their attractiveness with some hens having large fleshy combs on their heads whereas other females are barely ornamented at all. The size of a female’s comb relates to size of the eggs she lays. So by inseminating higher quality sperm into these females males have a greater chance of fertilising eggs that result in superior offspring.

OSB: How do they do it?
CC: They do this by allocating different amounts of seminal fluid to attractive and unattractive females. Sperm cells are the machines that swim, but to do so they need fuel and seminal fluid provides a crucial energy source. By allocating more seminal fluid to ejaculates males are able to increase the performance of their sperm.

OSB: How were you able to find this out?
CC: Since female attractiveness can easily be determined by measuring the size of the fleshy comb on top of their heads, we fitted attractive and unattractive females with a small harness that enabled us to collect sperm. After males had copulated with females we analysed ejaculates using computer aided sperm analysis software attached to a microscope that was originally designed for IVF programs. This software measures the speed at which sperm swim and this relates to how likely they are to fertilise eggs.

OSB: What are the implications of your findings?
CC: It has previously been shown in a number of species, including humans, that males can adjust the quality of sperm they ejaculate, but how they do this has remained a mystery. Our results show in chickens that cockerels do this by allocating more seminal fluid. This takes us one step further to understanding the factors that determine fertilisation success. We now have to assess what it is in the seminal fluid that makes sperm tick and if this is the case for other species.

OSB: What do we know about humans? Do men use similar strategies to chickens and is it even possible to do experiments to find out?
CC: The ability of males to adjust the quality of sperm they allocate to ejaculates has been shown to be extremely widespread. In fact it has been demonstrated in insects, fish, birds and mammals, including humans. However, it is not possible to tell whether males across all these species adjust their sperm quality using seminal fluid without conducting experiments specifically tailored to each species. I know that some colleagues are carrying out some experiments on humans at the moment so hopefully they will be able to answer part of this question soon.