বৃহস্পতিবার, ১৬ মে, ২০১৩

Making frequency-hopping radios practical

May 15, 2013 ? New hardware could lead to wireless devices that identify and exploit unused transmission frequencies, using radio spectrum much more efficiently.

The way in which radio spectrum is currently allocated to different wireless technologies can lead to gross inefficiencies. In some regions, for instance, the frequencies used by cellphones can be desperately congested, while large swaths of the broadcast-television spectrum stand idle.

One solution to that problem is the 15-year-old idea of "cognitive radio," in which wireless devices would scan their environments for vacant frequencies and use these for transmissions. Different proposals for cognitive radio place different emphases on hardware and software, but the chief component of many hardware approaches is a bank of filters that can isolate any frequency in a wide band.

Researchers at MIT's Microsystems Technology Laboratory (MTL) have developed a new method for manufacturing such filters that should improve their performance while enabling 14 times as many of them to be crammed on a single chip. That's a vital consideration in handheld devices where space is tight. But just as important, the new method uses techniques already common in the production of signal-processing chips, so it should be easy for manufacturers to adopt.

There are two main approaches to hardware-based radio-signal filtration: one is to perform the filtration electronically; the other is to convert the radio signal to an acoustic signal -- a physical vibration -- and then convert it back to an electrical signal. In work to be presented in June at the International Conference on Solid-State Sensors, Actuators and Microsystems, Dana Weinstein, the Steve and Renee Finn Career Development Assistant Professor of Electrical Engineering and Computer Science, and Laura Popa, a graduate student in physics, adopted the second approach.

Resonant ideas

Both types of filtration use devices called resonators, and acoustic resonators have a couple of clear advantages over electronic ones. One is that their filtration is more precise.

"If I pluck a guitar string -- that's the easiest resonator to think of -- it's going to resonate at some frequency, and it's going to die down due to losses," Weinstein explains. "That loss is related to, basically, energy leaked away from that resonance mode into all other frequencies. Less loss means better frequency selectivity, and mechanical acoustic resonators have less loss than electrical resonators."

Acoustic resonators' other advantage is that, in principle, they can be packed more densely than electrical-filtration circuits. "Acoustic wavelengths are much smaller than electromagnetic wavelengths," Weinstein says. "So for a given frequency, my mechanical resonator is going to be much smaller."

But in practice, the number of acoustic resonators in a filtration bank has been limited. The heart of any device that converts electrical signals to mechanical vibrations, or vice versa, is a capacitor, which can be thought of as two parallel metal plates separated by a small distance.

"The capacitors change the impedance" -- a measure of the ease with which a wave propagates -- "that the antenna sees, so you may have unwanted reflections back into the antenna," Weinstein says. "Each capacitor from each filter is going to affect the antenna, and that's no good. It means I can only have so many filters, and therefore so many frequencies that I can separate my signal into."

Another problem with acoustic resonators is that turning them on or off -- a necessary step in the isolation of a particular transmission frequency -- requires giving each resonator its own electrical switch. Traditionally, an incoming radio-frequency signal has had to pass through that switch before reaching the resonator, suffering some loss of quality in the process.

Switching channels

Weinstein and Popa solve both these problems at a stroke. Moreover, they do it by adapting a technology already common in wireless devices: a gallium nitride transistor.

Almost all commercial transistors use semiconductors: materials, like gallium nitride, that can be switched between a conductive and a nonconductive state by the application of a voltage. In Weinstein and Popa's new resonator, the lower "plate" of the capacitor is in fact a gallium nitride channel in its conductive state.

Switching that channel to its nonconductive state is like removing the lower plate of the capacitor, which drastically reduces the capacitors' effect on the quality of the radio signal. In experiments, the MTL researchers found that their resonators had only one-fourteenth the "capacitive load" of conventional resonators. "The radio can now afford to have 14 times as many filters attached to the antenna," Weinstein says, "so we can span more frequencies."

Switching the channel to its nonconductive state also turns the resonator off, so the researchers' new design requires no additional switch in the path of the incoming signal, improving signal quality.

Finally, the new resonator uses only materials already found in the gallium arsenide transistors common in wireless devices, so mass-producing it should require no major modifications of existing manufacturing processes.

Commercial adoption of cognitive radio has been slow for a number of reasons. "Part of it is being able to get the frequency-agile components and do it in a cost-effective manner," says Thomas Kazior, a principal engineering fellow at Raytheon. "Plus the size constraint: Filters tend to be big to begin with, and banks of tunable filters just make things even bigger."

The MTL researchers' work could help with both problems, Kazior says. "We're talking about making filters that are directly integrated onto, say, a receiver chip, because the little resonator devices are literally the size of a transistor," he says. "These are all on a tiny scale."

"They can help with the cost problem because these resonator-type structures almost come for free," Kazior adds. "Building them is part of the semiconductor fabrication process, using pretty much the existing fabrication steps that you're using to build the transistor and the rest of the circuits. You just may need to add one, or two at the most, additional steps -- out of 100 or more steps."

Source: http://feeds.sciencedaily.com/~r/sciencedaily/matter_energy/technology/~3/MGM2ZhYQt0Y/130515113914.htm

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ABC adds 14 new series for next season

NEW YORK (AP) ? ABC says it is adding 14 new shows to its lineup next season, including a spinoff of its fairytale drama "Once Upon a Time" and an action-adventure series drawn from the Marvel Comics world.

The network also said it's going to combine the two nights of "Dancing with the Stars" into one next season, airing a two-hour episode on Monday nights.

ABC joined other broadcast networks in presenting their 2013-2014 schedules to advertisers in New York.

"Marvel's Agents of S.H.I.E.L.D.," from hit-maker Joss Whedon, features Clark Gregg reprinting his role as Agent Coulson from Marvel's feature films.

Other new shows the network is adding to its schedule next season include "Super Fun Night," written by and starring "Bridesmaids" actress Rebel Wilson, and a Texas Rangers drama called "Killer Women."

Source: http://news.yahoo.com/abc-adds-14-series-next-season-160018766.html

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বুধবার, ১৫ মে, ২০১৩

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Google Play Music All Access Hands-On: All You Want (Minus Friends)

Today at its I/O developer's conference, Google launched Google Play All Access, its long-anticipated subscription music service. I just spent some time exploring the on-demand catalog as well as its radio and music discovery features. The service's UI is impressively fast and fluid. Indeed, it's minimal in all the right ways. If only it wasn't so lonely in there.

It's an Add-On to Google Play Music

All Access is an add-on to the Google Music storage locker that has existed since the end of 2011. That means that you can upload the music from your computer and then complete your collection from Google Play's enormous catalog of music.

It costs the same as Spotify, Rdio, et al. Once its introductory $8 promo-pricing is gone, All Access will cost $10 per month for the entire on-demand catalog, radio, and use on mobile devices. There are no tiered plans. It's the whole shebang or nothing.

The Web UI Is Fast and Intuitive

Navigating the catalog and the app's different features couldn't be easier. The design is simple but at the same time packed with functionality. When you hover over a rectangular icon for an artist or album you're immediately presented with graphics to play the music or the familiar Google "..." button that reveals a menu with more options.

The whole interface is refreshingly intuitive. You never hit a dead-end when you're moving about different sections of the service. Every time you want the name of an artist or an album or something to be clickable, it is.

The detail pages albums are really nice example of the myriad ways All Access makes your life easier. Besides a little info about the artist, there are obvious buttons that let you launch radio based on that album or to add it to your library.

The new Google Play Music App for Android is slick too

Same deal as the browser version. No dead ends. Swiping songs you dont want to listen to out of the play queue is very satisfying.

I love that "Share YouTube Video" is an option

YouTube videos are actually my de facto vector for sharing music with friends on Facebook and Twitter. If you share a Spotify link?or a link from any walled in garden?it inevitably means that someone won't be able to enjoy it.

Google built that behavior into All Access. Instead of having to go search for a YouTube video when I want to share something, I can just click "Share YouTube Video" and a pop up will present you with links for few versions (if they're available). It's easy, and it doesn't require your friends having a Google+ account to enjoy.

I don't love that the service only gets social with Google+

Then again, All Access doesn't have very good social skills. Facebook? Nope! Twitter? Nope! A real-time feed of what all of your friends are listening to? Nopenopenope!

If you'd like, though, you can choose share on Google+ because of course you can share on Google+. It feels awfully lonesome in there.

Listen Now is a convenient way to just put something on

Part of the problem with expansive streaming music services is that sometimes it's hard to figure out what jams your want to bust. The "Listen Now" tab is Google's answer to this problem. It's designed to provide you easy access to the radio stations and artists you like?as well as those it thinks you might like based on your activity. The straightforward tile design makes it simple enough to just impulsively click something and be done with it.

Radio is solid but unremarkable

This is the oldest trick in Pandora's box: New Order is your favorite band? "Age of Consent" is your favorite song? Type it in and you'll get a playlist. The playlists I got were great on some cursory inspection. Plenty of variety and even hints of robotic taste. It's nice that you can remove songs from your radio queue if you want.

Again, it's the UI that sets radio apart from competitors. There's a lot packed into a simple interface.

Should you ditch Spotify or Rdio?

Not yet. Take advantage of the free trial first. Google Play Music All Access has amongst the smoothest designs we've seen for something with so much horsepower. Unfortunately, it doesn't come with Spotify's great social integration baked-in?and the social integration it does have is half-baked.

Source: http://gizmodo.com/google-play-music-all-access-hands-on-all-you-want-mi-506844196

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Israel minister criticizes Russia over Syria arms

JERUSALEM (AP) ? An Israeli Cabinet minister is accusing Russia of destabilizing the Middle East by selling weapons to Syrian President Bashar Assad's regime.

Monday's remarks by Tourism Minister Uzi Landau are likely to raise tensions with Russia on the eve of Prime Minister Benjamin Netanyahu's visit to Moscow.

Netanyahu is expected to press President Vladimir Putin to halt the arms sales to Assad's government.

Russia has sided with Assad in Syria's civil war, sending him weapons and shielding him against Western attempts to impose international sanctions.

Israel is concerned advanced Russian weapons could fall into the hands of Lebanon's Hezbollah group, another Assad ally.

Landau says the Russian arms supplies "promote instability in the Middle East" and that "anyone who provides weaponry to terror organizations is siding with terror."

Source: http://news.yahoo.com/israel-minister-criticizes-russia-over-syria-arms-104032971.html

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Massage therapy shown to improve stress response in preterm infants

May 14, 2013 ? It seems that even for the smallest of people, a gentle massage may be beneficial. Newborn intensive care units (NICUs) are stressful environments for preterm infants; mechanical ventilation, medical procedures, caregiving activities and maternal separation create these stressful conditions.

Born under-developed, preemies have an immature autonomic nervous system (ANS), which controls stress response and recovery. For a preemie, even a diaper change is stressful and the immature ANS over reacts to these stressors. Since preterm infants can't process stressors appropriately, interventions are needed to enhance ANS function and maturity.

Massage therapy may reduce stress in preterm infants by promoting ANS development. A study published recently in Early Human Development, conducted by University of Louisville School of Nursing researcher Sandra Smith, PhD, and her team at the University of Utah, found massage therapy that involved moderate pressure and stroking of the soft tissues followed by flexing and extending the joints of the arms and legs increased heart rate variability (HRV) in male, but not in female preterm infants.

HRV is a measure of ANS function and development. Infants who are born at term gestation demonstrate increased HRV, but preemies typically show decreased HRV and an inability to appropriately respond to stressors. Massaged male preterm infants demonstrated increased HRV similar to term infants, which supports their ability to correctly respond to stressors.

Researchers measured HRV during periods of sleep and caregiving immediately after massage therapy at the end of the second week of study in 21 medically stable male and female preterm infants. There was no difference in HRV between female preterm infants that received massage and those that did not. HRV increased weekly in the four male preterm infants that received massage therapy but did not increase in the male infants that did not receive massages. This finding suggests that massage enhanced development of the ANS in male preterm infants and may improve preterm infant response to stressful events.

"We were surprised to learn the differences in the impact of massage therapy on preterm boys and girls," Smith said. "Boys who received massage therapy demonstrated increased heart rate variability, but the therapy did not seem to affect HRV in girls -- perhaps there are hormonal reasons for this difference."

Smith said future research is needed with a larger sample of preterm infants to understand how massage therapy affects ANS development, and to determine the mechanisms by which massage therapy promotes ANS function in preterm infants.

Source: http://feeds.sciencedaily.com/~r/sciencedaily/~3/WLmlYRksmMs/130514190641.htm

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মঙ্গলবার, ১৪ মে, ২০১৩

Sentences continue in Minn. Somali terror case

MINNEAPOLIS (AP) ? Two men who left Minnesota to join the terrorist group al-Shabab in Somalia were sentenced to three years in federal prison Tuesday, getting reduced sentences for their cooperation with the government's investigation into what has been called one of the largest efforts to recruit U.S. fighters into a foreign terror group.

Abdifatah Yusuf Isse and Salah Osman Ahmed both traveled to Somalia in 2007 and spent about a week in an al-Shabab training camp. They found a way to leave the camp once they learned what al-Shabab was all about.

They each pleaded guilty in 2009 to one count of providing material support to a terrorist group. They each faced a maximum of 15 years in prison. But prosecutors asked for sentences of around six to seven years because both cooperated with the investigation into recruiting and financing for al-Shabab.

U.S. District Judge Michael Davis gave the two men three years apiece, and they're expected to get credit for time served.

Later Tuesday, Davis handed down a 12-year sentence to Omer Abdi Mohamed, who has been characterized as a recruiter for al-Shabab in the U.S. He pleaded guilty in 2011 to one count of conspiracy to provide material support to terrorists. He also faced a maximum of 15 years in prison but prosecutors asked for less time because of his cooperation.

Unlike several other defendants in the case, Mohamed was not accused of traveling to Somalia to fight for al-Shabab, though he admitted to helping some Minnesota men get plane tickets to Somalia. During last year's trial of another defendant, witnesses said Mohamed used his knowledge of the Quran to convince young men that they had a duty to fight.

His attorney denied that he played any role in recruiting. But after that trial, Mohamed was re-arrested when the court learned he was working at a school. At the time, Davis called him "a danger to the community."

An Ohio man who admitted that he helped raise money so others could travel from Minnesota to Somalia was also sentenced Tuesday.

Ahmed Hussein Mahamud received three years in prison. He pleaded guilty in 2012 to conspiracy to provide material support to a foreign terrorist organization. He lived in Eden Prairie until 2011, when he moved to Ohio.

Three more people face sentencing later this week in this case and a case on terror financing.

Davis handed down two sentences in the long-running case on Monday. A man who authorities say played a key role in funneling young men from Minnesota to al-Shabab got 20 years in prison, while a foot soldier for al-Shabab, who participated in an ambush on Ethiopian troops, got 10 years.

"I'm going to take a chance on you," Davis told Isse when granting him a lesser sentence.

He pointed to Isse's decision to leave the al-Shabab training camp: "You devised a scheme to get away. That told me a lot about you. ... If you had been involved in the ambush, you'd be doing a lot of time."

Davis did not explain the 12-year sentence he handed down to Mohamed, who asked him for mercy and said he never would want to harm the U.S.

"I made a terrible, a wrong," Mohamed told the judge. "I regret it."

The courtroom was packed with dozens of his supporters, while others had to wait downstairs. Defense attorney Peter Wold told the judge about 200 Somali community members had written letters to the court on his behalf, calling him respectful, kind and helpful.

"I have a very strong community that knows my heart," Mohamed said.

Authorities say that more than 20 young men left Minnesota to join al-Shabab starting in 2007, when small groups of local Somalis began holding secret meetings to talk about returning to their homeland to wage jihad against Ethiopians. The Ethiopian army was brought into Somalia in 2006 by its weak U.N.-backed government, but the troops were viewed by many Somalis as invaders.

Davis, who has overseen these cases for years, said he still struggles to understand what would make young men from good families, who came to Minnesota as refugees, choose to return to violence.

"We have to figure out what's going on and try to make sure this never happens again," he said.


Follow Amy Forliti on Twitter: http://twitter.com/amyforliti .

Source: http://news.yahoo.com/sentences-continue-minn-somali-terror-case-224631987.html

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