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May 2004
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July 2004

Hi-Tech answer to Low-Life Students

BBC Education

New measures to help detect cheating students are being demonstrated at a meeting of the Plagiarism Advisory Service at Northumbria University. One new online service can scan 4.5 billion web pages so that lecturers can check the originality of the work submitted by students.

A survey of around 350 undergraduates found nearly 25% had copied text from another source at least once.

Student Tom Lenham said of the statistics: "That's a pretty modest interpretation of the situation at the moment."

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DVDs in the spotlight


Nowhere is the relevance of physics to everyday life more obvious than with the success of the DVD in the home-entertainment market. Sales of DVD players and recorders are booming, and last year consumers around the world spent over $20bn on DVD disks. In the UK, for instance, sales of DVD disks were more than twice those of video cassettes.

While physicists might sometimes complain about the "bad physics" in the movies that people watch on DVD, when making a case for the importance of their subject they should also stress that the relentless march of the DVD into homes is based on lots of "good physics" - as do the lens and visual-effects tools that are used in the film-making process.

DVD players and recorders, for instance, rely on an impressive mix of optics, electronics and mechanics to read to and write data on a plastic disk that is spinning at a frantic 10 800 revolutions per minute. The disks themselves are good examples of materials science in action, especially the DVD-RW disks that allow data to be overwritten again and again.

[The challenge is] to burn submicron marks with nanometre precision onto a disk that is spinning at nearly 200 kilometres per hour. This feat can be likened to the challenges of building a Formula 1 racing car -- the use of the latest technology in pursuit of speed. And like Formula 1 teams, the manufacturers of high-speed DVD drives have entered a fierce race to make sure that it is their name that is on the world's fastest DVD recorder.

However, there is clear finish line to this race: beyond a rotation speed of about 10 000 rpm the centrifugal force will cause a standard disk to explode. Current DVD drives are already able to read disks at speeds close to this mechanical limit, which is equivalent to a data rate of 176Mb per second. Writing information at such speeds, however, is a bigger challenge because the writing process is more complicated.

Electronics companies want to reach the maximum possible recording speed. Various tricks are also being used to increase the storage capacity of disks; these tricks include using lasers with shorter wavelengths and lens with higher numerical apertures to read and write the data.

When writing data at these speeds it is not enough to quickly turn the laser on and off in the hope that it has left ones and zeroes in the correct places: the way that the power of the laser varies with time has to be controlled very carefully, otherwise a whole host of problems will arise. So companies are developing materials that can melt and then crystallize on timescales of 10 ns for DVD-RW disks.

Meanwhile, electronics companies are preparing to go beyond DVD, and, as often happens, at least two competing technologies - HD-DVD and Blu-Ray - are jockeying for position. Both approaches rely on gallium-nitride lasers operating at a wavelength of 405 nm in the violet-blue part of the spectrum. Light-emitting gallium-nitride devices have become a billion-dollar industry since they were first demonstrated by Shuji Nakamura at the then little-known Japanese company Nichia in the mid-1990s; this growth looks set to continue. The use of violet-blue lasers will allow HD-DVD and Blu-Ray disks to store an enormous 50 GB of data.

Although these new disks will not be compatible with existing DVD systems, it looks as if both HD-DVD and Blu-Ray recorders will be able to play CDs and DVDs.

In the July issue of Physics World Jochen Hellmig of Philips Research Laboratories in Eindhoven in the Netherlands describes these latest developments in detail. May the approach with the best physics win.

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Could driverless trains break the Tube strike?

BBC News

While millions of London commuters struggled into work because of a drivers strike on the London Tube network, it was business as usual on one line at least. The Docklands Light Railway (DLR) is Britain's only driverless metro, but with more walk-outs in the capital threatened, the appeal of such systems could grow on passengers.

Europe's first driverless metro was opened in the northern French town of Lille in 1983 and expanded a decade later. Today, automatically operated commuter train systems are dotted around the world, from Copenhagen to Kuala Lumper; Paris to Taipei.

In New York, engineers have been busy converting the subway's L-line to driverless operation. The service will begin operating in "shadow" mode in October, with train operators still in full control. If all goes to plan then by next spring the trains will be driving themselves.

However, drivers will continue to ride the trains to allay passenger fears and step into the breach if things go wrong.

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Long distance microwave link over the Straits of Gibraltar

A great piece of do-it yourself engineering - and there are some nice calculations here as well...

This document outlines the physical and technical issues involved in establishing a WLAN connection capable of real file transfer speeds up to 5.5mb/s from Tarifa in Spain to Tangiers in Morocco. Connecting two continents, using the free 802.11 standard and free software.

It must be noted that the calculations in this document are derived from an amalgamation of equations found on the internet. There appear to be discrepancies between the various sources found, so should be used as guidance only. I shall visit the library in order to iron out the discrepancies.

The distance from Tarifa to Tangiers: 32,000 metres, mostly over water. There is a shorter link available to Ksar-es-Seghir, Morocco which is 20,000 metres.

  • Tarifa antenna position: On top of the castle (Castillo de Guzmán el Bueno) 20? metres above sea level.
  • Tangiers antenna position: Presently unknown.

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But it's OK for Adults...

shellen dot com

"I know I live in the future a bit, being an early adopter and all, but the future is grand - and highly recommended"

This is the confirmation email I received from TiVo after I:

  • Heard that Michael Moore was going to be on 60 Minutes
  • Was miles from home and wished I could somehow schedule my TiVo to record this show
  • Turned to my trusty Treo 600, and pointed the browser to Tivo Central Online to sign-in and schedule this recording
  • Return home to find 60 Minutes recorded perfectly per my request.

"From: TiVo - Your DVR

Your online request for "60 Minutes" has been received.
This program is now scheduled to record and appears in
the To Do List.

Best regards,


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Watching television IS bad for children... probably.

BBC Health

Watching too much television may distort the hormonal balance of adolescents and push many of them into early puberty, say researchers.

Italian researchers found children denied access to television for just one week experienced a 30% jump in their melatonin levels.The hormone is thought to prevent the early onset of puberty.

If confirmed, this would be the first sign of a direct physiological impact on television watching upon the young. Many researchers believe that exposure to on-screen violence and sex has a damaging psychological effect on children - although this theory is hotly disputed.

Researcher Professor Roberto Salti, of the Mayer Hospital at the University of Florence, said: "This is statistically a very significant result. It suggests that an excess of television (viewing) can modify some hormones."

Some animals use melatonin to time their reproduction, changing it to suit their environments. In humans, the hormone regulates the body's internal 'clock'. Levels are at their lowest in the daylight hours, but peak in the evening around eight o'clock as the body prepares for a night's sleep. Melatonin is also used as a means of regulating sleep patterns for travellers suffering from jet lag.

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Start Worrying

BBC Health

Previous generations worried about the Bomb.

It looks as though the greatest threat to our generation may yet turn out to be the Chicken.

Which would be funny if it weren't so damn frightening...

A new study suggests that bird flu is becoming more dangerous each year.

Scientists in China and the US injected mice with samples of avian flu virus which emerged in different years. They found that the newer forms of the virus kill more rapidly than their predecessors. The fear is that this will increase the risks to humans too.

Earlier this year a strain of bird flu called H5N1 killed 23 people in east Asia - the most in any year since the strain first emerged seven years ago. Now scientists have found evidence that it is mutating in ways which make it more lethal. They took 21 different samples of H5N1 isolated over the years since 1997, and injected them into mice. A strong pattern emerged - the most recent viruses kill the mice much faster - which would suggest it's also becoming more lethal to humans.

However, as Professor Robert Webster, from St Jude Children's Research Hospital in Memphis points out, it has not yet acquired the most dangerous mutation. He said: "The thing that's lacking so far in these viruses is the ability to transmit human to human. And that's the trick that we hope they don't achieve; but if they do, then we have very big problems."

Professor Webster's team has been able to document some of the genetic changes in the virus and understand what they do - for example enabling it to evade bits of the human immune system. However, other mutations remain a mystery. Professor Webster believes the mutations may be caused by the virus jumping from species to species. As well as becoming more lethal, H5N1 is also now able to reproduce in more parts of the body than before.

The concern is that the virus will eventually accumulate enough genetic changes to become good at passing between humans. Even more of a concern would be the sudden change that could be caused should the flu combine with a human flu in someone's body. The two viruses could swap genes and create a potent hybrid as deadly as the bird strain and as contagious as a regular human strain.

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A-level theft inquiry widens

BBC Education

The theft of A-level exam question papers from a college in north-west London was bigger than thought.

Papers from all three of the main exam boards may have been stolen, and more of Edexcel's than previously reported.

In all, the authorities are watching for signs of cheating in at least 20 exam units, some of them GCSEs.

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