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Monthly Archives: October 2011

The Iris Code

Today, most commercial iris-recognition systems use an algorithm developed by John Daugman of the University of Cambridge and patented worldwide in 1992.

Daughman’s insight lay in computerising a process to mathematically analyse the random patterns visible within the iris image to create a binary code called an iris code. This code is so individual to a person – even identical twins have different iris codes – that only 70 per cent of its needs to match for an iris comparison to be considered successful. The change of a greater than 70 per cent match between two irises is less than 1 in 10 billion.

YOUR IRIS NEVER LIES
A scan that looks for similarities between irises will make it harder to construct a false identity
By Lakshmi Sandhana – New Scientist 15th October 2011

IRIS images may soon be able to do more than just verify your identity – they may confirm your race and gender too.

The iris controls the size of the pupil and gives a person’s eyes their colour. It grows into a complex and unique pattern as a foetus develops and remains the same throughout a person’s life. The fact has been successfully exploited in iris-based biometric systems, which work on the principle that each iris is completely different to any other.

But that is not strictly true, as Kevin Bowyer at the University of Notre Dame in South Bend, Indiana and his colleagues have found. They have developed a system that can pick up similarities between irises, instead of differences. Initial tests show it can distinguish between people of two different racial backgrounds and show promise in determining gender.

“You might assume that there is no similarity in iris texture,” says Bowyer, “but you would be wrong.”

In a typical iris scan, a camera snaps an image of a person’s eye while it is bathed in near-infrared light. Software identifies the iris portion of the eye, and then analyses 1024 sample regions, looking for patterns in the way the delicate filaments of tissue, known as the stroma, reflect light. This unique information is then used to generate a code of binary numbers.

Bowyer’s team’s method adds a layer of complexity. For each of the sample regions, their software identifies features such as lines or spots in the stroma, and saves that information. It also records how brightness varies across each region.

This richer set of attributes allowed the researchers to train an algorithm to look for common features among irises of known ethnicity and gender. When they turned the system on a database of unknown irises of 1200 people, it predicted whether a person was Chinese or Caucasian with over 90 per cent accuracy, and correctly identified gender 62 per cent of the time. The team will present the research next month at the IEEE International Conference on Technologies for Homeland Security in Waltham, Massachusetts.

The reason for the low success rate in predicting gender, Bowyer says, is because the team have not fully worked out which textural features of the iris correspond to gender. He says that the fact that the results are better than chance means it should b possible to improve the system’s ability to determine gender. The team has also not yet tested the system on people with other or more complex ethnic backgrounds.

Aside from making it difficult for people to fabricate a false identity in which they have a different gender or race, the method could speed up searches within large iris databases by reducing the data subset to be searched. It would also be possible to count the number of people belonging to different ethnic backgrounds coming into a country without recording their identity.

“It is interesting work that does fly a bit in the face of conventional thinking.” says Vijayakumar Bhagavatula of Carnegie Mellon University in Pittsburgh, Pennsylvania. Iris patterns are generally considered to be highly random; even a person’s left and right iris are different. Still, he says, “in the absence of a established biological connection between iris pattern and gender or ethnicity, there is no way to know if the features being used by Bowyer are the ‘best’ ones to use. They may be other features that given better prediction rates.”

 
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Posted by on October 17, 2011 in Science

 

The Rhythms of Life

Linda Geddes – New Scientist

Monkseaton High School in Tyneside, UK has seen some amazing improvements in the past year. Absenteeism is down, punctuality is up and exam results have gone through the roof. Head teacher Paul Kelly cannot attribute these successes to better teaching or stricter discipline, instead, he simply started opening the school at 10am instead of 9 am.

The change was designed to synchronise the school day with pupils’ body clocks. Teenagers are notoriously owlish, preferring to stay up into the small hours and sleep in till lunchtime. This isn’t entirely their own fault: natural delays in secretion of sleep hormone melatonin causes their body clocks to be shifted several hours backwards. By aligning the school day with this biological rhythms. Monkseaton school avoids teaching teenagers when their brains are still half asleep.

In the modern world our lives are largely dictated by time. But even in the absence of clocks, schedules and calendars, our bodies still march to the beat of the internal timekeepers called circadian rhythms. Over each 24-hour period we experience cycles of physical and mental changes that are thought to prepare our brains and bodies for the tasks we’re likely to encounter at certain times of the day.

The most obvious is the sleep-wake cycle, but there are many others, Circadian rhythms affect everything from how we perform on physical and mental tasks to when drugs are more likely to be effective. “We’re not the same organism at midday and midnight,” says Russell foster, who researches circadian rhythms at the University of Oxford.

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The main driver of circadian rhythms is a tiny patch of brain tissue called suprachiasmatic nucleus (SCN), located just above the optic nerves. This master clock gathers information about the light from the retina and relays it to the rest of the body via nerve impulses and hormones.

Among these are the sleep hormone melatonin and its opposite number orexin. The SCN also imposes its rhythms on the immune function, digestion, cell division, body temperature and more. Its own pattern of activity is reset each day by light, and this influences the expression of a handful of “clock genes” whose activity follows a 24-hour cycle.

The SCN isn’t the be-all and end-all of biological timekeeping. Many of the body’s cells also contain clocks on their own which have peaks troughs of activity throughout the say. For example, inflammation-causing  immune cells called mast cells are more active in the early morning, which may be why immune disorders such as asthma are more troublesome at this time. Skin cells also show circadian rhythms, proliferating at nigh and producing more oil during the day, while cells in the stomach that release the hunger hormone ghrelin also seem to be controlled by a circadian clock.

These local clocks are not completely independent of the master clock. The SCN is thought to act like the conductor of an orchestra, producing a regular signal from which the rest of the musicians take their cues. “If you shoot the conductor, the members of the orchestra will keep on playing, but they’re all playing at slightly different times so the rhythmicity falls apart,” says Foster. People whose SCN stops functioning because of injury or disease lose their regular 24-hour cycle.

Not surprisingly, our physical and mental states vary widely with the time of the day. For example, core body temperature is at its lowest at around 4.30 am, rises through the day and peaks at around 7pm. Adrenalin levels also rise throughout the day.

These changes can affect how we perform on various tasks. “There is fairly comprehensive evidence of circadian rhythms in many aspects of human performance, including athletic,” says Jim Waterhouse of Liverpool John Moores University, UK. As your body temperature and adrenalin levels rise during the afternoon, physical performance tends to improve. Meanwhile the ability to carry out complicated mental tasks like decision-making is negatively affected the longer you have been awake.

Not everyone follows the same pattern. Some people are larks, preferring to rise early and retire early, while owls find it difficult to function in the morning but thrive late at night. These “chronotypes” are largely determined by genes. Most of us fall somewhere in the middle.

At the extreme end of the spectrum are people with a rare but somewhat treatable disorder called familial advanced sleep-phase syndrome (FASPS), who wake naturally in the early hours of the morning and fall asleep in the early evening. We now know that FASPS is caused by a single mutation in a gene called PER2, one of a handful clock genes responsible for setting the SCN.

Clocks can also be nudged forwards by exposure to bright light in the early morning, through preliminary evidence suggests that some people’s clocks are more resistant to resetting than others, says Steven Brown of the University of Zurich in Switzerland. This might explain why some people are more susceptible to jetlag and find it harder to adapt to shift work than other people.

Age can also cause profound shifts in your body clock. Older people tend to sleep less and wake earlier. Brown’s lab recently discovered a factor in the blood of elderly people that can shift the circadian rhythms of skin cells towards the lark end of the spectrum (Proceedings of the National Academies of Science, Vol 108, P 7218).

This discovery suggests it might be possible to develop drugs that turn owls into larks and vice versa. “That could be useful not only for older individuals, but for shift workers and people with sleep syndromes,” says Brown. Though don’t hold out any hope of sleepy teens ever being bright eyes and bushy tailed at 9 am.

Linda Geddes – New Scientist (8th October 2011)

 
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Posted by on October 13, 2011 in Science

 
 
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