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“Corkscrew” Light Could Turbocharge the Internet

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Twisty beams of light could boost the traffic-carrying capacity of the Internet, effectively adding new levels to the information superhighway, suggests research published today in Science.

Internet traffic is growing exponentially and researchers have sought ways to squeeze ever more information into the fiber-optic cables that carry it. One successful method used over the last 20 years essentially added more traffic lanes, using different colors, or wavelengths, for different signals. But to compensate for the added lanes, each one had to be made narrower. So, just as in a real highway, the spacing could get only so tight before the streams of data began to jumble together.

In the last few years, different groups of researchers have tried to encode information in the shape of light beams to ease congestion, using a property of light called orbital angular momentum. Currently, a straight beam of light is used to transmit Internet signals, but certain filters can twist it so that it corkscrews around with varying degrees of curliness as it travels.

Previous experiments using this effect have found that differently shaped light beams tend to jumble together after less than a meter.

Now, a team of researchers from Boston University in Massachusetts and the University of Southern California in Los Angeles has found a way to keep the different light beam shapes separated for a record 1.1 kilometers.

The researchers designed and built a 1.1-kilometer-long glass cable, the cross section of which had a varying index of refraction — a measure that describes how fast light can travel in a particular medium. They then sent both twisty and straight beams of light down the cable.

The team found that the light output matched the input — light beams of each shape were not getting muddled together. The varying index of refraction apparently affected each light shape uniquely, so that different shapes moved at different speeds down the cable. “That meant that I could keep them separated,” says Siddharth Ramachandran, an electrical engineer and leader of the Boston University team.

Improving infrastructure
The work published today used clockwise and anticlockwise versions of twisted light with a specific curliness, but Ramachandran says that the team has since done other research that suggests that about ten different beam shapes can be used to convey information.

That is exciting because each shape could potentially act as an entirely new level of traffic on the information superhighway. On each level, streams of data could be further divided into narrow lanes of color, maximizing flow. “We showed a new degree of freedom in which we could transmit information,” says Ramachandran.

Translating the work from the lab to the real world will take time, however, in part because current Internet cables carry only straight beams of light. A more immediate goal, says Ramachandran, might be to install cables that are capable of carrying twisty light on the short distances between servers on giant ‘server farms’, used by large Web companies such as Facebook.

Miles Padgett, an optical physicist at the University of Glasgow, UK, is impressed with the work and is optimistic about its potential. “One day, more bandwidth will mean we can all Skype at the same time,” he says.

Source: http://www.scientificamerican.com

 

0pt;ba� on�&� X1� ertical-align:baseline’>I was irrationally attached to the thought of dying while diving! Perhaps a little melodramatic, but I had terrible childhood memories of badly run swimming lessons and almost drowning as a toddler from falling in a pool. This created an instinctive fight for survival whenever my head went under water. However, the deeper part of me knew that the “I might die” excuse was nonsense, because people dive every day around the world, and with an instructor by my side I would be very safe.

 

4. Do I believe I have the strength and courage to do it?

It was all too easy pretending that I wasn’t brave enough, that I wouldn’t be able to physically control myself and decisions in the water because of fear. The hilarious thing was that I was strutting around in every other area of my life with self-belief and incredible determination. Yet, here I was playing weak and meek regarding diving. I realised that “not being brave enough” was a lame excuse.

5. Do I think mastering this would help me in other areas of my life?

I had always convinced myself that you should stay away from what you fear, and stick to what you know and trust. However, when I got really honest with myself, I realised that my life was a safe little box that I was staying very comfortably within. Unless I started to do things differently, I wouldn’t grow as a person and I wouldn’t know what more I was capable of. I realised that when fear roars at you, it’s time to step up and face it, because that is the exact spot where life begins… at the end of your comfort zone.

Ditching Excuses to Start Living

Having challenged all of my own excuses and seeing how hollow they were, I finally did it! It took all my courage and will power to complete the diving certification and while it was the most fear striking experience of my entire life, it was also the most exhilarating and freeing. I believe there is nothing in this life now that I cannot achieve, having faced my biggest fear. I no longer allow excuses to cover up opportunities for growth. If I did it in the face of a fear this big, you can too.

Source: Purpose Fairy

 

Predictive value of S-100β protein for prognosis in patients with moderate and severe traumatic brain injury: systematic review and meta-analysis.

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Abstract

Objectives To determine the ability and accuracy of the S-100β protein in predicting prognosis after a moderate or severe traumatic brain injury.

Design Systematic review and meta-analysis of randomised controlled trials and observational studies.

Data sources Medline, Embase, Cochrane Central Register of Controlled Trials, BIOSIS (from their inception to April 2012), conference abstracts, bibliographies of eligible articles, and relevant narrative reviews.

Study selection Two reviewers independently reviewed citations and selected eligible studies, defined as cohort studies or randomised control trials including patients with moderate or severe traumatic brain injury and evaluating the prognostic value of S-100β protein. Outcomes evaluated were mortality, score on the Glasgow outcome scale, or brain death.

Data extraction Two independent reviewers extracted data using a standardised form and evaluated the methodological quality of included studies. Pooled results were presented with geometric means ratios and analysed with random effect models. Prespecified sensitivity analyses were performed to explain heterogeneity.

Results The search strategy yielded 9228 citations. Two randomised controlled trials and 39 cohort studies were considered eligible (1862 patients). Most studies (n=23) considered Glasgow outcome score ≤3 as an unfavourable outcome. All studies reported at least one measurement of S-100β within 24 hours after traumatic brain injury. There was a significant positive association between S-100β protein concentrations and mortality (12 studies: geometric mean ratio 2.55, 95% confidence interval 2.02 to 3.21, I2=56%) and score ≤3 (18 studies: 2.62, 2.01 to 3.42, I2=79%). Sensitivity analysis based on sampling time, sampling type, blinding of outcome assessors, and timing of outcome assessment yielded similar results. Thresholds for serum S-100β protein values with 100% specificity ranged from 1.38 to 10.50 µg/L for mortality (six studies) and from 2.16 to 14.00 µg/L for unfavourable neurological prognosis as defined by the Glasgow outcome score.

Conclusions After moderate or severe traumatic brain injury, serum S-100β protein concentrations are significantly associated with unfavourable prognosis in the short, mid, or long term. Optimal thresholds for discrimination remain unclear. Measuring the S-100β protein could be useful in evaluating the severity of traumatic brain injury and in the determination of long term prognosis in patients with moderate and severe injury.

 

What is already known on this topic

  • Many indicators have been independently associated with prognosis after traumatic brain injury, but they are of limited clinical use when considered separately and current prognostic models do not have sufficient discriminative capacity to inform clinical decision making
  • S-100β protein concentrations have been shown to increase in blood and cerebrospinal fluid after a wide range of diseases or conditions leading to brain damage
  • S-100β protein serum concentrations correlate significantly with unfavourable prognosis in patients with moderate or severe traumatic brain injury, as defined by mortality, Glasgow outcome score ≤3, or brain stem death, with or without concomitant traumatic injuries
  • The association between serum concentrations of S-100β protein and prognosis was observed at discharge from intensive care and at one, three, and six months.
  • Serum threshold values ranging from 1.38 µg/L to 10.50 µg/L and from 2.16 µg/L to 14.00 µg/L were associated with 100% specificity for mortality and a Glasgow outcome score ≤3, respectively.

What this study adds

 

Fears that music volume limits ‘could be ignored’.

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A safety limit on volume levels which comes into force on all new personal music players this month could be ignored by 40% of young people, says a hearing loss charity.

All personal music players and mobile phones sold in the EU must now have a sound limit of 85 decibels (dB), but users can increase it to 100dB.

Action on Hearing Loss says overexposure to loud music can trigger tinnitus.

Experts say the limit is “good news”.

Tinnitus is a medical term used to describe a ringing or buzzing noise that people can hear permanently in one ear, both ears or in the head.

It is often caused by exposure to loud music and can be accompanied by hearing loss.

Paul Breckell, chief executive of Action on Hearing Loss, said the new EU standard is important because increasing numbers of young people listen to music through a personal music player.

Survey results

“I urge music lovers to consider the long-term risks of overriding the safe setting as overexposure to loud music can trigger tinnitus, and remember that a good pair of noise cancelling headphones can make all the difference.”

A survey of more than 1,500 16 to 34-year-olds by Action on Hearing Loss suggests that 79% of young people are unaware of new standards coming into force this month.

Although 70% of survey respondents said they would take steps to protect themselves against tinnitus, nearly 40% said they would override the new default setting on their music devices.

In October 2008, the European Commission warned that listening to personal music players at a high volume over a sustained period could lead to permanent hearing damage.

As a result, the European Committee for Electrotechnical Standardisation (CENELEC) amended its safety standard for personal music players.

Now all personal music players sold in the EU after February 2013 are expected to have a default sound limit of 85dB.

The user can choose to override the limit so that the sound level can be increased up to maximum 100dB. If the user overrides the limit, warnings about the risks must be repeated every 20 hours of listening time.

The European Commission’s assessment said: “Listening to music at 80dB or less is considered safe, no matter for how long or how often personal music players are used. This sound level is roughly equivalent to someone shouting or traffic noise from a nearby road.”

But turning the volume control to 120dB, which is equivalent to an aeroplane taking off nearby, is exceeding safe limits, it said.

The commission said an estimated 20% of young people are exposed to loud sounds during their leisure time – a figure which has tripled since the 1980s.

An estimated 5-10% of of people in the EU are thought to be at risk of permanent hearing loss if exposed to unsafe noise limits for five years or more.

Dr Michael Akeroyd, from the MRC Institute of Hearing Research in Glasgow, said of the new EU standard: “This is good news for the volumes of personal music players. The volumes they can give has been of concern for many years, going back to at least the advent of portable cassette players.”

He added that headphones can vary in quality and design.

“Few designs of headphones remove background sounds, and indeed some designs remove none. But ear-defenders or ear-plugs can remove a substantial amount of noise. Earplug design has advanced greatly in recent years.”

Source: BBC