Saturday, May 30, 2015

[tt] WaPo: You've heard about distracted driving; are you ready for distracted walking?

It was some decades ago when I first read that half of those
killed in pedestrian-vehicle fatalities were drunk at the time, the same
as the percentage of vehicle fatalities involving drunk drivers.


You've heard about distracted driving; are you ready for distracted walking?
http://www.washingtonpost.com/local/trafficandcommuting/youve-heard-about-distracted-driving-are-you-ready-for-distracted-walking/2015/05/27/864d8e40-04a4-11e5-a428-c984eb077d4e_story.html
By Ashley Halsey III May 27 at 8:23 PM Follow @ashleyhalsey3rd

Back in the quaint old 20th century, people used to disparage a
person of dull intellect by saying he couldn't walk and chew gum at
the same time.

How times and technology have changed things. And a new phrase has
entered the lexicon: distracted walking.

That would apply to people who can't walk and use their cellphones
without getting themselves injured.

The National Safety Council has rolled out statistics on the myriad
ways that Americans got themselves injured or killed in 2013.

It was the council's annual accounting of things gone wrong in the
home, on the job and on the roadways, in 200-plus pages of fairly
depressing but cautionary statistics.

You must stifle your desire to ridicule those who are injured while
walking around texting or talking on their cellphones, just as it
probably was unfair in the past century to mock those who could not
chew while they walked.

For starters, some who are more mindful of their social-
media interactions than of their personal safety end up in the
emergency room.

One study cited by the council found that between 2000 and 2011,
more than 11,000 people were injured while walking and talking on
their phones.

"We've seen dramatic increases in injuries serious enough to require
emergency-department visits since 2000," said Kenneth P. Kolosh, the
safety council's manager of statistics. "And we also see that half
of these cases involve cellphone-distracted walking that occurred in
the home, so it's not just walking down the street."

Most of the people who reported to emergency rooms with injuries
related to distracted walking were women younger than 40. Nearly
80 percent of injuries were the result of falls, and 9 percent of
those who suffered injuries simply walked into something with enough
force to hurt themselves.

The range of injuries is impressive. Lots of dislocations or broken
bones (25 percent), strains or sprains (24 percent), and plenty of
concussions or contusions (23 percent).

Distracted-walking injuries are not exclusively a young person's
affliction: 42 percent of the injured were younger than 30, but
there was a healthy representation of victims from older
generations.

"We have 20 percent of these injuries happening to individuals at 71
years of age or more," Kolosh said. "This is impacting all age
groups, not just the young, heavy users as you might expect."

Another bad outcome of people's fiddling with their mobile devices
is far more dangerous than falls and fractures. The council report
said that 26 percent of all traffic accidents are linked to drivers
using their cellphones, including for texting.

The council estimated that 21 percent of vehicle accidents were
attributable to drivers' talking on cellphones, while 5 percent of
drivers involved in accidents were writing or reading text messages.

The report said that unintentional injuries were the fifth-leading
cause of death in the United States, after heart disease, cancer,
respiratory disease and stroke.

The number of people who died because of unintentional injuries in
2013 was 130,800, an increase of 2.4 percent from the previous year.
The number of roadway deaths declined, while other deaths in public
and at home increased.

In addition to those who died in 2013, about 39 million people
received medical attention for injuries, the report said. The
economic impact of the deaths and nonfatal, unintentional injuries
was calculated to be $820.6 billion, the report said.

The National Safety Council is a 102-year-old nonprofit organization
originally chartered by Congress.

Ashley Halsey reports on national and local transportation.
_______________________________________________
tt mailing list
tt@postbiota.org
http://postbiota.org/mailman/listinfo/tt

[tt] NS 3022: Einstein and Schrödinger: The price of fame

NS 3022: Einstein and Schrödinger: The price of fame
http://www.newscientist.com/article/mg22630221.400-einstein-and-schrodinger-the-price-of-fame.html
* 23 May 2015 by Michael Brooks

From personal feuds to fruitless quests to overhaul quantum theory,
the two physics legends fought hard to maintain their fame, argues a
new book

* Book information
* Einstein's Dice and Schrödinger's Cat: How two great minds
battled quantum randomness to create a unified theory of physics
by Paul Halpern
* Published by: Basic Books
* Price: $27.99

THESE are the good times. A few years ago, I was at a dinner during
a Solvay Conference - the triennial gathering to discuss enduring
problems in physics and chemistry. Looking around, I asked a
physicist I knew who he thought was the smartest person there.
Almost without hesitation, he pointed to a dark-haired young man a
few tables away.

I was a little surprised. There were at least three Nobel laureates
in the room for starters, plus a number of highly respected
scientists that I knew by sight. I didn't have a clue who the young,
dark-haired man was. Now I do: the man was Juan Maldacena.

But in 100 years, will anyone write about Maldacena's life in
physics? Almost certainly not, because he is now 46 and no cult of
personality has yet grown up around him. What's more, his work is
not easy to appreciate in terms non-physicists can understand. But
the most crucial missing ingredient may be this: Maldacena doesn't
seem that concerned with self-promotion. In other words, he doesn't
have what set Albert Einstein and Erwin Schrödinger apart.

Paul Halpern's fascinating book is, in many ways, a study of the
long tail that marks many distinguished careers in science. In
physics and mathematics, people tend to do their best work early on.
What then? Strive for further accomplishments, or invest in the next
generation?

There can be no doubt about the enormous scale of Einstein and
Schrödinger's contributions. Einstein deserves to be the world's
most famous physicist for his 1905 work alone. Special relativity,
the photoelectric effect and his explanation of Brownian motion were
all stunning contributions. This year we are celebrating the
centenary of Einstein's general theory of relativity. Created in his
mid-30s, this was yet another gigantic deposit into the bank of
human knowledge.

Schrödinger's contribution was slightly less extraordinary -although
still more extraordinary than most physicists manage in a lifetime
of research. His wave equation, describing the behaviour of quantum
objects such as subatomic particles, revolutionised our
understanding of, and our ability to manipulate, the fundamentals of
matter.

Halpern, a professor of physics, takes the time to explain the
intricacies and significance of the two men's work in wonderfully
clear ways. He employs helpful analogies and metaphors to lower the
reader gently into a strange new world where electrons jump like
dancers under strobe lights, and the mathematical metric tensor of
general relativity is a sewing pattern for the canopy of space-time.

Neither Schrödinger nor Einstein liked what they found in the
subatomic world. The particles exhibit properties that are not
traceable to any cause, but take on random values. There is no
certainty, only probability. Hence Einstein's famous phrasing of his
disbelief: God doesn't play dice.

Schrödinger's most famous cultural contribution - the cat that is
simultaneously dead and alive because nothing has forced it to take
on a definite character - was born out of a similar dismissal of
what seemed absurd and unphysical in the theory both men had helped
to create.

For most of their careers, Schrödinger and Einstein were convinced
that quantum theory was in need of a major overhaul. Halpern reports
how Einstein's obsession showed during a lecture given in the
presence of Danish physicist Niels Bohr, often considered the
founding father of quantum theory. "At the end of the talk," he
writes, "Einstein gazed directly at Bohr and said that his goal was
to replace quantum mechanics. Bohr glared back but didn't say a
word."

Schrödinger and Einstein both spent far longer on the hunt for a
unification of quantum physics and relativity than they had on the
breakthroughs for which they are known. This quixotic quest forms
the major part of Halpern's book, and it makes for a tragic tale.

Einstein revised and rejigged his work, to the increasing ennui of
his peers and the increasing adulation of the world. Schrödinger,
never as famous, overstepped the mark, trying so hard to be taken
seriously that he offended Einstein with public pronouncements about
the superiority of his own work. For three years, Einstein didn't
return Schrödinger's letters.

Their fellow physicists became more bewildered and irritated by the
pair. It is tough for physicists to see the public offer awe and
respect for ideas that are unproven speculation. It was especially
galling when it became clear that both men were writing
pre-publication summaries of their research for newspaper reporters
to work from - then complaining about subsequent press attention.

As Halpern makes clear in entertaining and evocative prose, these
were also frustratingly fruitless times for Einstein and
Schrödinger. What's more, very little of the scientific wisdom and
insight the two men had amassed was passed to students or junior
colleagues who might have helped take their work forward. The only
real beneficiaries were the institutions whose reputations their
presence enhanced.

Not that the legacy is totally lost. Maldacena is at one of these
institutions - the Institute for Advanced Study in Princeton. Unlike
Einstein, though, he collaborates and publishes with colleagues on a
wide range of topics. But Maldacena is just one of many fine minds
who are making inroads where Einstein and Schrödinger made none.

Anyone given to muttering about things being better in the old days
should read Halpern's insightful book to appreciate that, relatively
speaking, we've never had it so good.

Michael Brooks is host of New Scientist's Instant Expert -
Einstein's Universe, at the British Library, London, 23 May. More
information and tickets at bit.ly/1Pdyknl

[tt] NS 3022: Clare Wilson: Good Looking (7 articles plus leader)

NS 3022: Clare Wilson: Good Looking (7 articles plus leader)
http://www.newscientist.com/article/mg22630220.700-good-looking-phone-screens-that-do-the-focusing-for-you.html
et seq.
* 22 May 2015
Clare Wilson is a medical reporter at New Scientist

1. Phone screens that do the focusing for you

Put away those reading glasses. A new type of screen will make any
page look just right for your eyes

The lenses in our eyes get stiffer as we age, making it harder to
focus on things that are close up. This is why people start to need
reading glasses from their 40s onwards. Eventually, nearly everyone
will own a pair. But it can be a pain putting on your glasses every
time you look at your phone, for instance, assuming you can remember
where you put them.

Glasses work by partly focusing light before it hits the eye - so if
you are looking at a screen, why not make it do the focusing for
you? A team at the Massachusetts Institute of Technology has shown
that plastic screen covers can correct for all kinds of vision
problems - effectively, the screen wears the glasses. But rather
than making plastic covers tailored to individuals' eyes, the team
want to exploit the ability of existing 3D screens to control the
direction of light. The idea is that instead of providing a 3D
image, users could adjust the screen settings to "pre-focus" light
as their eyes require.

Few handheld devices have 3D screens so far, but something similar
can be done with software alone. "We know how the eye works so we
mathematically invert that and compute the image," says Daniel
Aliaga, a computer vision researcher at Purdue University in West
Lafayette, Indiana, who helped develop the idea. The software
distorts images on the screen in such a way that it mimics the
effect of a lens bending the light rays before they reach the eye.
"It looks weird to anyone else but to you it looks sharp," says
Aliaga.

The approach works with both text and images, he says, so with
pre-focused screens people would no longer need reading glasses. The
Purdue team's start-up, called CPrecisely, is developing apps that
can modify the text on ebooks, phones and computers. The first
product, a free alarm clock phone app, is due for release this year.
"Imagine you're in bed and you want to see what time it is," says
Aliaga. "Instead of searching for your glasses you just pick up your
phone."
---
2. The veggies that really do boost night vision

No, carrots can't help you see in the dark. But some other veggies
might

During the second world war, British propagandists circulated
rumours that RAF pilots were such good night fliers because all the
carrots they ate helped them to see in the dark. In reality the
British were trying to keep their use of radar secret.

Yet it turns out that there is some truth to the idea that diet can
affect our eyes. Retinal cells contain three yellow pigments -
lutein, zeaxanthin and meso-zeaxanthin - which absorb
near-ultraviolet light, protecting the eye from its damaging effects
and reducing glare. These pigments are concentrated in the centre of
the retina that produces the sharp central area of our vision, the
macula. "It's like wearing internal sunglasses," says Billy Hammond
of the University of Georgia in Athens. "It reduces the light
intensity and absorbs scatter."

We get these pigments from food, and the richer our diet is in them,
the higher the levels in our macula. In theory then, people of any
age could boost their eyesight by improving their diet or taking
supplements. A large trial of supplements is due to finish in July,
but a smaller one, in which 36 people took a pill containing all
three pigments every day for six months, has already yielded
positive results.

The effect was big enough that people should have noticed the
difference when coping with the glare of car headlights at night,
for instance, says team member John Nolan, a nutrition and vision
researcher at Waterford Institute of Technology in Ireland.

Nolan says boosting macular pigment levels should be even better
than wearing yellow-tinted glasses for driving at night, as some
people do, because such glasses block blue light from the whole of
the retina. Extra macular pigment, by contrast, doesn't stop the
light reaching the retinal cells outside the macula, so peripheral
vision is not reduced.

Nolan already takes the supplements himself, and thinks taking all
three is important. Hammond, however, thinks it is best to get these
compounds from your diet, by eating plenty of vegetables - kale,
spinach and red peppers are among the best sources. Eggs are
another. "We like things to seem like drugs, but you'd always be
better off just eating some spinach," Hammond says.

A diet rich in macular pigments could not only improve your sight,
it might actually save it. As we get older the retinal cells in the
macula often become damaged. As the disease progresses, people
develop a blurred patch in the centre of their vision that gets
worse. Over a quarter of over-75s have macular degeneration, making
it the biggest cause of blindness in Western countries.

As there is no cure, the best approach is to detect macular
degeneration early and try to stop it progressing. Telltale yellow
spots appear in the tissue underlying the retina before symptoms
appear. Trials have shown that people in the early stages of the
disease who take supplements of macular pigments, vitamins C and E,
and zinc are 25 per cent less likely to suffer deterioration in
their vision.
---
3. Super lens implants are going mainstream

Novel kinds of artificial eye lenses are allowing both the
short-sighted and long-sighted to see fine without glasses, even for
reading

The natural lenses in the eye tend to become cloudy in old age, with
more than half of people over 80 developing the problem in at least
one eye. It has long been routine to treat cataracts, as they are
called, by replacing the lens with an artificial one.

The standard replacement lenses, however, can only focus light from
distant objects, unlike the natural lens, which changes shape to
focus on different distances. That means people still need reading
glasses after a cataract operation.

Over the past decade, replacement lenses have been introduced that
mimic the variable focusing power of the natural lens, meaning many
people who have cataract surgery can dispense with glasses
completely. "I've had 82-year-old patients who've worn glasses since
they were 8," says Anne Sumers, an ophthalmologist in Ridgewood, New
Jersey, and a spokesperson for the American Academy of
Ophthalmology. "It's so exciting for them."

There are several designs. One type, for instance, is made in such a
way that it has different light-bending powers at different places
within the lens. The brain somehow pays attention only to the light
rays that give the sharpest image for the object you want to see and
ignores the rest. "The visual cortex chooses the points of best
focus," says Bruce Allan, a surgeon at Moorfields Eye Hospital in
London. "Everything else is photoshopped out."

Cataract surgery is a no-brainer if you need it, whatever kind of
replacement lens you get. However, there are now also other kinds of
implants designed specifically to replace glasses. One type is for
people who are so short-sighted that they can't have corrective
laser surgery as it would cut away too much of their cornea. Known
as intraocular collamer lenses, these implants are inserted just in
front of the natural lens. "It's like putting spectacles inside the
eye," says Allan.

Another kind of implant, called corneal inlays, treat the
long-sightedness that comes with age, so you could throw away your
reading glasses. But there have been reports of side effects so the
jury is still out safety-wise.
---
4. Keep moving if you want to keep seeing

One of the many benefits of exercising is that it helps to protect
against various forms of blindness as we get older

Doing eye exercises won't stop you needing glasses (see Game on).
But ordinary exercises like running might just save your sight as
you get older.

Running or walking reduces your chances of getting cataracts,
according to a massive study that followed over 40,000 people for
six years. According to a smaller study, running also reduces the
risk of macular degeneration - the leading cause of blindness in
developed countries. The exact mechanism isn't clear in either case,
but exercise is of course known to have a whole host of benefits.

Another common eye disorder is diabetic retinopathy, when the blood
vessels of the retina overgrow or leak. This can damage the retina,
affecting vision, and eventually lead to blindness. All the things
that help prevent type 2 diabetes, such as exercise, also help
prevent diabetic retinopathy.

People can also have the equivalent of a stroke within the eye if a
clot blocks one of the blood vessels that feed the retina. Such
"retinal vein occlusions" can trigger transient or even permanent
loss of vision.

The best way to avoid one is to do all the things that prevent a
stroke in the brain, says Anne Sumers, a spokesperson for the
American Academy of Ophthalmology. Stay active, watch your blood
pressure and cholesterol levels, and above all, don't smoke.
---
5. Video games that can help you see better

Playing shoot 'em ups has a surprising benefit - it can train your
brain to sharpen your vision

In his 1920 book Perfect Vision Without Glasses, William Bates
claimed that doctors did not understand how the eye works and that
anyone could achieve perfect vision by, for example, staring at the
sun (do not try this at home!). His mad ideas remain popular to this
day: countless books and websites still claim that "natural vision
correction" can be achieved simply by doing eye exercises.

In fact, there is no evidence that any kind of exercise improves the
eye's focusing powers, which is the cause of most vision problems.
But there is evidence that the brain can get better at interpreting
the signals it receives from the eyes. The main focus of research
has been contrast sensitivity - how well we can discern things that
are only slightly darker or lighter than their surroundings. It is
important for reading in poor light, say, or driving at night.

There have been some apparently impressive results reported with
training schemes involving Gabor patches. These look like blurry
lines, and the exercises typically involve spotting ever-fuzzier
lines that get harder and harder to distinguish from the background.
One recent study suggests that older people, who tend to have worse
contrast sensitivity, could regain similar abilities to those in
their early 20s.

Several apps are now on sale so you can try these exercises at home,
but it's not yet clear whether they improve vision in real life or
just make people better at detecting Gabor patches. Most eyesight
specialists want to see more controlled trials done before they
recommend their use. "It's probably too soon to know," says James
Tsai, an ophthalmologist at Yale University.

In the meantime, some of the strongest evidence that brain training
can improve vision comes from studies of computer gamers. Daphné
Bavelier, a neuroscientist now at the University of Geneva,
Switzerland, first became aware of the effect after some students
who were keen gamers scored more highly than expected on vision
tests.

Her team has been studying this phenomenon ever since. They have
shown that people who spend a lot of time playing action games have
better contrast sensitivity than non-players. Not only that, but
when they asked people who don't usually play these games to do so
for 6 hours a week for nine weeks, their contrast sensitivity
improved by 43 per cent.

The effect is strongest with so-called first-person shooters, which
some claim increase violent behaviour. "It's the games that are
ostracised," says Bavelier. For comparison, non-gamers who played
The Sims for six weeks only improved by 11 per cent. However, it
might be possible to create games that have the same effect as
first-person shooters without the violence.

The people in her study were all in their 20s and already had good
vision, so Bavelier doubts they would notice the effect on their
vision in everyday life. Some of her volunteers spotted one result
of the training, though: the screens of old-style cathode-ray tube
monitors seemed to start flickering because their vision was now
sharp enough to spot the pixels being refreshed. Fortunately, that
side effect doesn't happen with modern LCD screens.

Bavelier thinks that computer-game-based brain training is most
likely to produce meaningful improvements in vision in people who
already have problems, although her team has yet to demonstrate
this. In theory, older people with declining contrast sensitivity
stand to benefit most. The trouble is that most action video games
are too fast for older adults, Bavelier says, but some researchers
are creating games specifically for them.

Brain training is also showing great promise as a treatment for
what's called lazy eye, where the brain ignores the input from one
eye, often because of a squint in childhood. It affects about 3 per
cent of the population.

The standard treatment is to put a patch over the good eye to force
the brain to use the bad one, but children sometimes refuse to
cooperate, leading to permanent vision problems. The brain-training
approach involves playing the computer game Tetris through special
goggles, so that one eye just sees the falling blocks and the other
sees the shapes at the bottom of the screen they slot into. The game
can be played only if the brain uses both eyes, working together.

In one study, after 10 hours of training, vision improved
dramatically in the lazy eyes of 18 adults, equivalent to 2 or 3
lines on an eye chart. The biggest surprise was that adults were
able to benefit at all, as patching does not work in children over
12, says Robert Hess, an ophthalmologist at McGill University in
Montreal, Canada, who led the work. "There's no current treatment
for adults," he says.

A commercial version of the training game, called Dig Rush, is now
being developed for home use. It uses cheap 3D glasses to show
different images to each eye.
---
6. How time outdoors could protect kids' eyesight

The increase in short-sightedness in kids across the world is often
blamed on time in front of a screen, but a lack of time outdoors may
be the real problem

Short-sightedness is becoming more common in most rich countries,
and is skyrocketing in certain parts of Asia; in Singapore, for
instance, 80 per cent of young adults are now myopic. So why the
increase?

Myopia typically arises when the eyeball grows too long, causing
light from distant objects to be focused in front of the retina
rather than on it. Because the condition is commoner among those who
are more educated, the obvious conclusion is that the development of
the eye can be affected by spending too much time reading. But it's
not quite that simple.

Some studies have found that the less time children spend outdoors,
the more likely they are to become short-sighted. Such findings
suggest that it is not book or computer work that is harmful per se,
but failing to look into the distance. "A hunter-gatherer would have
spent a lot of time seeing things at a distance - not 12 inches in
front of their face," says Billy Hammond, a visual neuroscientist at
the University of Georgia in Athens.

Not all researchers agree that looking at distant things is the key;
some think that the brightness or quality of outdoor light is what
matters. But for now, giving children regular doses of the great
outdoors seems to be the best bet for avoiding short-sightedness.
And it has a whole host of other benefits too.
---
7. 6 surprising ways to improve your eyesight

Not many of us have perfect eyesight, and we will develop problems
as we get older. Until recently, glasses or contact lenses were just
about the only options.
But as we've learned more about the eye, we've come up with
surprising ways to preserve or enhance vision, from changing what
you eat to software that lets you read your smartphone without
reading glasses.

TECHNOLOGY

Phone screens that do the focusing for you

Put away those reading glasses. A new type of screen will make any
page look just right for your eyes

FOOD & DRINK

The veggies that really do boost night vision

No, carrots can't help you see in the dark. But some other veggies
might

SURGERY

Super lens implants are going mainstream

Novel kinds of artificial eye lenses are allowing both the
short-sighted and long-sighted to see fine without glasses, even for
reading

EXERCISE

Keep moving if you want to keep seeing

One of the many benefits of exercising is that it helps to protect
against various forms of blindness as we get older

GAMING

Video games that can help you see better

Playing shoot 'em ups has a surprising benefit - it can train your
brain to sharpen your vision

...AND FOR CHILDREN

How time outdoors could protect kids' eyesight

The increase in short-sightedness in kids across the world is often
blamed on time in front of a screen, but a lack of time outdoors may
be the real problem

VIDEO

Watch: Ways to improve your eyesight

Because glasses are far from the only way to see better...

OPINION

It's time to focus on the global tragedy that is impaired vision

Uncorrected eyesight is one of the biggest - and most overlooked -
health issues. Fortunately, creative new remedies are bringing
clearer vision to everyone

TECHNOLOGY

Goodbye, paper: What we miss when we read on screen

Digital technology is transforming the way we read and write. Is it
changing our minds too - and if so, for better or worse?

HEALTH

Guilty pleasures: Can you ease the effects of drinking too much?

FEATURE: 22:00 28 May 2015

Overdoing the alcohol can take a serious toll on your health, but
there a few clever ways to help you feel better, faster

Lost memories recovered in mice with a flash of light

DAILY NEWS: 19:00 28 May 2015

Traces of "forgotten" memories lurk in the brain and can be revived
with the right tools - raising hopes of new ways to help people with
Alzheimer's or amnesia

Guilty pleasures: How much chocolate can your body handle?

FEATURE: 14:00 28 May 2015

If a pang of guilt after demolishing a bar of chocolate is all too
familiar, find out the true effect of your sweet fix - and how to
make it more virtuous

Brain implant that decodes intention will let us probe free will

DAILY NEWS: 18:00 27 May 2015

Designed to give paralysed people more independence, the implant
also lets us see if brain activity can show a person's decisions -
before they realise they've made any
---
Leader: It's time to focus on the global tragedy that is impaired vision -
opinion - 22 May 2015 - New Scientist
http://www.newscientist.com/article/mg22630223.400-its-time-to-focus-on-the-global-tragedy-that-is-impaired-vision.html
* 22 May 2015

Poor eyesight isn't just a nuisance: it destroys lives. Fortunately,
creative new remedies are bringing clearer vision to everyone

EVEN if it hasn't happened to you yet, it may only be a matter of
time. Blurry vision, a trip to the optician for glasses or contact
lenses - or, if you find such aids to be a nuisance, corrective
surgery.

Newer remedies range from basic dietary tweaks to ingenious
self-focusing phone screens (see "Good looking: Phone screens that
do the focussing for you"). They are sorely needed: impaired vision
is one of the world's commonest ailments - and becoming commoner
still. Myopia, which already affects nearly half of Westerners, and
a majority of people in some Asian countries, is on the up and up.
The causes of this rise in short-sightedness are complex, but
probably largely environmental (Opthalmology, doi.org/4q7).

Modern Western lifestyles are key, but this is a growing problem in
the developing world, too. The World Health Organization estimates
that 153 million people globally have uncorrected vision. Many have
no access to eye care at all, or can't afford it anyway.

That is a tragedy, not a nuisance. Uncorrected vision keeps people
out of work and education; only cataracts cause more preventable
blindness. The Centre for Vision in the Developing World, set up by
University of Oxford physicist Joshua Silver, says that by 2030
eyesight will be one of the world's top 10 health issues in terms of
productivity and opportunities - taking a bigger economic toll than
the HIV epidemic.

The single biggest problem is a lack of trained specialists and
access to corrective lenses. Sierra Leone, for example, has only one
optometrist treating a population of 6 million people. But there are
rays of hope. A new WHO drive has prompted governments to take
action, and cheap, innovative solutions are emerging. Silver has
pioneered spectacles that the wearer can fill with liquid until
their vision is corrected, and the OneDollarGlasses project is
training cadres of opticians, who travel with ultra-cheap,
pre-ground polycarbonate lenses for insertion in simple spring steel
frames. There is still a long way to go. But at least we are now
focusing on the problem.

[tt] NS 3022: Elizabeth Landau: The big bang blip: Solving the mystery of why matter exists

NS 3022: Elizabeth Landau: The big bang blip: Solving the mystery of why
matter exists
http://www.newscientist.com/article/mg22630220.600-the-big-bang-blip-solving-the-mystery-of-why-matter-exists.html
* 20 May 2015

Elizabeth Landau is a science writer in Pasadena, California. She
Tweets as @lizlandau

Matter and antimatter should have wiped each other out at the
universe's birth. The upgraded Large Hadron Collider aims to find
why matter alone survived

IT'S an odd thought that the banana on your kitchen counter,
squished in your lunch bag or tucked away in your desk drawer is the
embodiment of one of the universe's great mysteries, just waiting to
be unpeeled.

Whatever its state of ripeness, that banana is made of particles of
matter, just like you: its intrinsic matteryness is why you can see,
feel and taste it. What you don't see is what a banana does 15 times
a day or so. Blip! It produces a particle of something else,
something that vanishes almost instantaneously in a flash of light.

That something else is antimatter.

The prediction, and subsequent discovery, of antimatter counts as a
great triumph of physics. It represents a whole mirror world of
particles, identical in mass to those of normal matter, but with
opposite electrical charge. But it seems rather an afterthought. In
our neck of the woods, antimatter particles are only produced during
interactions of high-energy cosmic rays in the atmosphere, or in
radioactive decays - such as those from the tiny amount of
radioactive potassium-40 every banana contains.

In one sense that's unsurprising, given that antimatter and matter
"annihilate" whenever they meet, giving out a puff of energy in the
form of light. In our matter-dominated world, antimatter simply
doesn't stand a chance. But for physicists studying the fundamentals
of the material world, the imbalance is deeply unsettling. According
to their best-laid theories, the big bang should have created matter
and antimatter in exactly equal amounts. In the orgy of annihilation
that followed, the cosmos would have been left filled with nothing
but a sea of light.

But it wasn't. Some blip at the beginning of the universe caused
some matter to survive - and make everything from bananas to black
holes, seahorses to stars. It didn't need much: calculations show a
difference of just one part in a billion would have been enough.
"It's that one-part-in-a-billion more matter that forms the universe
that we're in now," says physicist Tara Shears of the University of
Liverpool, UK. But how did it happen?

At Geneva International Airport on the French-Swiss border, it's
easy to miss that such deep questions are being explored in an
underground cavern just a kilometre away. Planes take off and land
tantalisingly close to the building that houses the control room of
the experiment Shears works on, LHCb. This detector at CERN's Large
Hadron Collider - the $10 billion particle smasher buried beneath
Geneva's outskirts - isn't as famous as its two bigger cousins,
ATLAS and CMS. They garnered glory back in 2012 for co-discovering
the elusive Higgs boson particle, the signature of an all-pervasive
field that gives the basic particles of matter mass.

But LHCb is after an even more fundamental prize.

The b stands for beauty - not as in salons, but as in quarks. Quarks
are the fundamental particles found in the protons that the LHC
smashes to smithereens. There are six types of quark, and they all
have the odd quirk that they are never found by themselves, but
always bundled into larger composite particles made up of two, three
or possibly more (see "Tetraquirk?"). Protons, for example, are made
up of three of the lightest - two up quarks and one down quark.

These days, the beauty quark is often more prosaically called the
bottom quark, or just b. It is much more massive than the up and
down quarks, but thanks to Einstein's E = mc^2, particles containing
more massive quarks can be made from the energy liberated in the
LHC's proton collisions. One example would be particles called B
mesons, which contain either a b quark or its antimatter equivalent,
as well as one other quark.

B mesons could hold the key to how matter came to win out over
antimatter. To understand why, we must rewind 50 years, to the
discovery in the 1960s of a phenomenon known as charge-parity (CP)
violation. James Cronin and Val Fitch later won the 1980 Nobel prize
in physics for showing that, under certain circumstances,
antiparticles decay at different rates from their matter
counterparts.

It was just the sort of thing that might explain matter's dominance,
but unfortunately the effect was far too small even to explain a
one-in-a-billion imbalance. Subsequent experiments such as BaBar at
SLAC National Accelerator Laboratory in California and Belle at the
KEK Laboratory in Japan have shown that CP violation also occurs
when particles containing b quarks decay, and the imbalance is
greater in this case (see diagram). "The behaviour of the matter
version and the antimatter version of the beauty quark happen to be
the most different of any fundamental particle that we've studied,"
says Shears. "We don't know why, but it means we can measure it with
more accuracy."

Even so, decays of known particles so far account for only about one
part in a trillion of the CP violation needed to explain the
universe. Meanwhile, the discovery of the Higgs boson has only
deepened the mystery. Its mass of 125 gigaelectronvolts and observed
decay rate fit predictions from the standard model of particle
physics, a theoretical construct laboriously built up over decades,
boringly well. If it had defied them, that might have pointed to the
influence of particles as-yet unknown - which might have provided
another source of CP violation.

No such luck. "The known type of CP violation we have in the
equations so far is not enough. Now that we know more about the
Higgs particle, it's not enough to explain the matter-antimatter
asymmetry in the universe today," says Matt Strassler, a theorist at
Harvard University. "People are looking for something wrong with the
equations, something wrong with the standard model, something beyond
it."

And perhaps unexpectedly, that throws the focus back on B mesons.
The "beauty factories" BaBar and Belle collided electrons and their
antimatter equivalents, positrons, with energies in the range of
billions of electronvolts - enough to produce only the lightest B
mesons in appreciable numbers. But to arrive at any meaningful
answer as to why matter's dominance arose, we need to recreate the
more energetic conditions of the cosmic primordial soup.

After a two-year shutdown, the LHC is now expected to produce
collisions releasing 13 trillion electronvolts of energy, at a
higher rate than ever before, bringing us much closer to doing that.
The results could perhaps open up a crack between experiments and
standard-model predictions. "The energy increase brings us increased
B particle yields that will allow more sensitive studies of CP
violation in areas we have not yet probed," says LHCb physicist
Sheldon Stone of Syracuse University in New York state.

And LHCb is custom-made to do that. It is a relatively small fish in
a big pond - or perhaps more appropriately, given the LHC's
27-kilometre circular structure, in a very large moat. ATLAS and CMS
each cost seven times as much to build, and have three times as many
researchers working on them. But unlike these general purpose
detectors, which were built to observe all sorts of particles
created in the energetic melee of the LHC's collisions, LHCb is more
choosy. Whereas ATLAS and CMS are cylindrical, fully encompassing
the point at which the protons collide, LHCb's detectors are in a
cone or wedge shape, with the collisions taking place at the pointy
end.

That makes the experiment much less sensitive to detecting Higgs
bosons, which tend to emerge at high angles outside LHCb's zone of
detection. But it's just the thing for measuring B mesons, which
tend to be produced with their momentum directed along the line of
the original proton beams. "For certain measurements, LHCb is the
best game in town," says Strassler.

Not that getting hold of a B meson is easy. They are produced
travelling close to the speed of light and exist for just 10^-12
seconds before decaying. That's not long, but it is an eternity
compared with some other particles: those containing the even
heavier top quarks, for example, decay after just 10^-20 seconds.
Crucially, it means B mesons carve characteristic trails through the
LHCb detectors that are a centimetre or so long - long enough for
the LHCb's analysis teams to begin to get a handle on them. "That's
what we do," says Stone. "That's what we live on."

Recent results from data taken before the LHC's shutdown, presented
earlier this year at a conference in La Thuile, Italy, suggest
something interesting. They confirm earlier hints of deviations from
standard-model predictions in the rare decay of a B meson to a K
meson and two muons, heavier versions of the electron. The signal
isn't yet certain enough to tell if some unknown physics is
responsible for the anomaly, or whether it can help to explain the
matter mystery. Following up on that lead is a priority for LHCb's
physicists once the LHC is fully rebooted.

Another focus is the decay of a different beauty-containing
particle, the "B-sub-s", or strange B meson. This agglomeration of a
b-antiquark and a strange quark can transform into its antiparticle
incredibly fast, so looking at whether the reverse process happens
in the same way would provide another avenue to study CP violation.
Also, three times in every billion, it decays into a muon and an
antimuon. This decay may be rare, but its end state is very easy to
see because muons leave a trail right through the detector all the
way to the outermost layer. That makes it a "golden channel" to
search for new physics, says Shears.

Here the interest may not just be in CP violation, but also in hints
of phenomena predicted by theories such as supersymmetry. SUSY
proposes the existence of a raft of exotic particles and might
explain a lot of things the standard model can't, such as why the
fundamental forces have very different strengths, and the nature of
the mysterious dark matter that seems to make up most of the stuff
in the cosmos. But if these particles truly exist, their masses are
so large that neither the LHC nor any other particle smasher has
created them to date (7 March, p 30).

Rare B-meson decays should be especially susceptible to the
influence of unseen massive particles, perhaps giving the LHCb
experiment a sneaky way to prove their existence without detecting
them directly. Any deviation from B-mesons' expected rates of decay
could mean hidden particles are participating in a "ghostly manner",
says Guy Wilkinson of the University of Oxford, the leader of the
LHCb collaboration.

The strange B meson decay is so unusual that experiments to date
have seen very few examples, although both LHCb and CMS did spot it
happening in 2013. More observations with the revamped LHC could
make all the difference. "If you have certain varieties of
supersymmetry as the real nature of the universe, then the way in
which this particle behaves is modified, and it can produce these
pairs of muons more often or less often," says Shears. "It's a very,
very precise probe of what could be out there."

Nonetheless, this particular decay hasn't yielded any insights into
why the fates of matter and antimatter were so very different.
"Unfortunately, it all matches up with our predictions," says
Shears.

It sounds a little funny to hear experimental physicists say it's
unfortunate how well theory and experiment match, but it's a refrain
Stone echoes. "It's not a big deal," he says about the strange B
meson findings so far, but then pauses and corrects himself: "The
result is a big deal, but unfortunately it confirmed the standard
model. That's the problem."

That yearning for something new will continue as long as that
existential question of what caused the blip at the beginning of the
universe remains unanswered.

Maybe, just maybe, LHCb will be the underdog experiment to satisfy
that longing as the LHC kicks back into gear. "For the first time,
we're going to a regime in the universe where what we really need to
see, and what we're really looking to see, is the unexpected," says
Shears.

And if we do find a convincing explanation for the matter around us
any time soon - well, that really would be reason to go bananas.

Tetraquirk?

There are six types of quark: up, down, strange, charm, bottom (or
beauty) and top (or truth). Each has an antimatter doppelganger that
is identical in mass, but has opposite electrical charge.

Quarks of any kind only ever turn up in larger composite particles.
Heavier "baryons" contain three quarks, as the familiar proton and
neutron do; they also have antimatter equivalents containing three
antiquarks. Lighter mesons contain a quark and an antiquark.

That might not be the whole story, though. Before the LHC's recent
two-year shutdown, the LHCb experiment amassed the most significant
evidence yet for the existence of tetraquarks - particles with four
quarks.

The standard model doesn't explicitly limit the number of quarks in
a single particle, but if tetraquarks do exist they represent a
whole new form of matter beyond the pairs and triplets previously
confirmed, says Eric Swanson of the University of Pittsburgh. "Now
comes along another option for the first time."

More observations of LHCb's particular tetraquark find - the jazzily
named Z(4430) - could give us a better understanding of how quarks
are glued together. More broadly, it could tell us what exotic
states of matter may have existed when the universe was just a baby
- another insight into matter's mysterious early history (see main
story).


_______________________________________________
tt mailing list
tt@postbiota.org
http://postbiota.org/mailman/listinfo/tt

[tt] NS 3022: The internet is running out of room - but we can save it

NS 3022: The internet is running out of room - but we can save it
http://www.newscientist.com/article/dn27536-the-internet-is-running-out-of-room--but-we-can-save-it.html
* 16:00 15 May 2015 by Jacob Aron

Are we running out of internet? It might sound like an odd question,
but researchers met at the Royal Society in London this week to
discuss a coming internet "capacity crunch", and what we might do
about it.

The meeting sparked headlines warning of a "full" internet and the
potential need for data rationing, but the reality is more nuanced.
The crunch is real, caused by fast growth of online media
consumption through the likes of Netflix and Youtube, but physics
and engineering can help us escape it. The internet just needs a few
tweaks.

Fear of a capacity crunch stems from a hard physical truth - there
is a limit to the amount of information you can cram down any
communications channel, fibre-optic cable or copper wire. Discovered
in 1940 by Claude Shannon, this limit depends on the channel's
bandwidth - the number of frequencies it can transmit - and its
signal-to-noise ratio (SNR).

Digital traffic jam

The information capacity of optical fibres - the light-carrying
pipes that form the backbone of the internet - can be increased
simply by increasing the power of the light beamed through them.
This boosts the signal that encodes, say, a Netflix show so that it
dominates over the inherent noise of the fibre, making it easier to
read at the other end.

Researchers have spent decades finding ways to amplify signals,
increasing the capacity of fibre already in the ground and keeping
up with the growth of internet traffic.

But that trick has hit a dead end. If you up the power beyond a
certain point, the fibre becomes saturated with light and the signal
is degraded. This limit means fibres as we currently use them are
nearing their full capacity. "You can't get an infinite amount of
capacity in a fibre," Andrew Ellis at Aston University in
Birmingham, UK, who organised the meeting, told New Scientist.

René-Jean Essiambre of French communications firm Alcatel-Lucent
presented research suggesting the limit is around 100 terabits per
second, or 250 Blu-ray discs-worth. The internet's fibre systems
could reach this in the next five years, he warned.

Fight fibre with fibre

Don't cancel the Netflix account just yet, though. Polina Bayvel of
University College London presented work designed to compensate for
distortion in the optical fibre at high power. Her technique
analyses interference within the fibre as light travels through. It
then rapidly calculates how the light was distorted, allowing the
recipient to clean up the signal at the other end. "You receive a
mess, and by carrying out these steps you are able to reconstruct
the signal digitally," she said.

David Richardson of the University of Southampton, UK, is
investigating new fibres that contain multiple cores for
transmitting data, effectively many fibres in one. These are more
difficult to make than conventional fibres because the cores are
tiny and must keep their shape across kilometre-long cables, but
they're capable of handling much more data.

Techniques like these will be key to fighting capacity crunch, says
Ellis. But if researchers aren't able to scale up and commercialise
their solutions, rationing or other restrictions on internet use may
be the only option.

"I don't see a crisis in the internet," Andrew Lord, a researcher at
UK telecom company BT, told the meeting. "I've got a lot of faith in
the ingenuity of people to keep delivering the goods," he told New
Scientist.

Friday, May 29, 2015

[tt] (MIT) Algorithm reduces size of data sets while preserving their mathematical properties

[

http://newsoffice.mit.edu/2015/algorithm-shrinks-big-data-0520

]

(... links deleted ...)

* Illustration: Jose-Luis Olivares/MIT
[126]Full Screen

To handle big data, shrink it

Algorithm reduces size of data sets while preserving their mathematical
properties.

Larry Hardesty | MIT News Office
May 20, 2015
[127]Press Inquiries [128]Share

Press Contact

Abby Abazorius
Email: [129]abbya@mit.edu
Phone: 617-253-2709
MIT News Office

Media Resources

1 images for download

[130]Access Media

Media can only be downloaded from the desktop version of this website.

Share

Comment

[131]Leave a comment

As anyone who's ever used a spreadsheet can attest, it's often
convenient to organize data into tables. But in the age of big data,
those tables can be enormous, with millions or even hundreds of
millions of rows.

One way to make big-data analysis computationally practical is to
reduce the size of data tables — or matrices, to use the mathematical
term — by leaving out a bunch of rows. The trick is that the remaining
rows have to be in some sense representative of the ones that were
omitted, in order for computations performed on them to yield
approximately the right results.

At the ACM Symposium on Theory of Computing in June, MIT researchers
will present a new algorithm that finds the smallest possible
approximation of the original matrix that guarantees reliable
computations. For a class of problems important in engineering and
machine learning, this is a significant improvement over previous
techniques. And for all classes of problems, the algorithm finds the
approximation as quickly as possible.

In order to determine how well a given row of the condensed matrix
represents a row of the original matrix, the algorithm needs to measure
the "distance" between them. But there are different ways to define
"distance."

One common way is so-called "Euclidean distance." In Euclidean
distance, the differences between the entries at corresponding
positions in the two rows are squared and added together, and the
distance between rows is the square root of the resulting sum. The
intuition is that of the Pythagorean theorem: The square root of the
sum of the squares of the lengths of a right triangle's legs gives the
length of the hypotenuse.

Another measure of distance is less common but particularly useful in
solving machine-learning and other optimization problems. It's called
"Manhattan distance," and it's simply the sum of the absolute
differences between the corresponding entries in the two rows.

Inside the norm

In fact, both Manhattan distance and Euclidean distance are instances
of what statisticians call "norms." The Manhattan distance, or 1-norm,
is the first root of the sum of differences raised to the first power,
and the Euclidean distance, or 2-norm, is the square root of the sum of
differences raised to the second power. The 3-norm is the cube root of
the sum of differences raised to the third power, and so on to
infinity.

In their paper, the MIT researchers — Richard Peng, a postdoc in
applied mathematics, and Michael Cohen, a graduate student in
electrical engineering and computer science — demonstrate that their
algorithm is optimal for condensing matrices under any norm. But
according to Peng, "The one we really cared about was the 1-norm."

In matrix condensation — under any norm — the first step is to assign
each row of the original matrix a "weight." A row's weight represents
the number of other rows that it's similar to, and it determines the
likelihood that the row will be included in the condensed matrix. If it
is, its values will be multiplied according to its weight. So, for
instance, if 10 rows are good stand-ins for each other, but not for any
other rows of the matrix, each will have a 10 percent chance of getting
into the condensed matrix. If one of them does, its entries will all be
multiplied by 10, so that it will reflect the contribution of the other
nine rows it's standing in for.

Although Manhattan distance is in some sense simpler than Euclidean
distance, it makes calculating rows' weights more difficult.
Previously, the best algorithm for condensing matrices under the 1-norm
would yield a matrix whose number of rows was proportional to the
number of columns of the original matrix raised to the power of 2.5.
The best algorithm for condensing matrices under the 2-norm, however,
would yield a matrix whose number of rows was proportional to the
number of columns of the original matrix times its own logarithm.

That means that if the matrix had 100 columns, under the 1-norm, the
best possible condensation, before Peng and Cohen's work, was a matrix
with hundreds of thousands of rows. Under the 2-norm, it was a matrix
with a couple of hundred rows. That discrepancy grows as the number of
columns increases.

Taming recursion

Peng and Cohen's algorithm condenses matrices under the 1-norm as well
as it does under the 2-norm; under the 2-norm, it condenses matrices as
well as its predecessors do. That's because, for the 2-norm, it simply
uses the best existing algorithm. For the 1-norm, it uses the same
algorithm, but it uses it five or six times.

The paper's real contribution is to mathematically prove that the
2-norm algorithm will yield reliable results under the 1-norm. As Peng
explains, an equation for calculating 1-norm weights has been known for
some time. But "the funny thing with that definition is that it's
recursive," he says. "So the correct set of weights appears on both the
left-hand side and the right-hand side." That is, the weight for a
given matrix row — call it w — is set equal to a mathematical
expression that itself includes w.

"This definition was known to exist, but people in stats didn't know
what to do with it," Peng says. "They look at it and think, 'How do I
ever compute anything with this?'"

What Peng and Cohen prove is that if you start by setting the w on the
right side of the equation equal to 1, then evaluate the expression and
plug the answer back into the right-hand w, then do the same thing
again, and again, you'll quickly converge on a good approximation of
the correct value of w.

"It's highly elegant mathematics, and it gives a significant advance
over previous results," says Richard Karp, a professor of computer
science at the University of California at Berkeley and a winner of the
National Medal of Science and of the Turing Award, the highest honor in
computer science. "It boils the original problem down to a very
simple-to-understand one. I admire the mathematical development that
went into it."

(... links deleted ...)

[181]Massachusetts Institute of Technology

[182]MIT News Office • [183]Building 11-400
[184]Massachusetts Institute of Technology • Cambridge, MA 02139-4307

[185]Back to the top

References

126. http://newsoffice.mit.edu/sites/mit.edu.newsoffice/files/images/2015/MIT-RowSampling-1.jpg
127. http://newsoffice.mit.edu/2015/algorithm-shrinks-big-data-0520#press-inquiry-section
128. http://newsoffice.mit.edu/2015/algorithm-shrinks-big-data-0520#share-choices
129. mailto:abbya@mit.edu
130. http://newsoffice.mit.edu/media-download?article=31620
131. http://newsoffice.mit.edu/2015/algorithm-shrinks-big-data-0520#separator-comments

Reprinted with permission of MIT News (http://newsoffice.mit.edu/)
_______________________________________________
tt mailing list
tt@postbiota.org
http://postbiota.org/mailman/listinfo/tt

[tt] (MIT) Researchers build new fermion microscope

[

http://newsoffice.mit.edu/2015/fermion-microscope-0513

]

(... links deleted ...)

* Graduate student Lawrence Cheuk adjusts the optics setup for laser
cooling of sodium atoms.
Graduate student Lawrence Cheuk adjusts the optics setup for laser
cooling of sodium atoms.
Photo: Jose-Luis Olivares/MIT
[126]Full Screen
* Laser beams are precisely aligned before being sent into the vacuum
chamber. Laser beams are precisely aligned before being sent into
the vacuum chamber.
Photo: Jose-Luis Olivares/MIT
[127]Full Screen
* Sodium atoms diffuse out of an oven to form an atomic beam, which
is then slowed and trapped using laser light.
Sodium atoms diffuse out of an oven to form an atomic beam, which
is then slowed and trapped using laser light.
Photo: Jose-Luis Olivares/MIT
[128]Full Screen
* A Quantum gas microscope for fermionic atoms. The atoms,
potassium-40, are cooled during imaging by laser light, allowing
thousands of photons to be collected by the microscope.
A Quantum gas microscope for fermionic atoms. The atoms,
potassium-40, are cooled during imaging by laser light, allowing
thousands of photons to be collected by the microscope.
Credit: Lawrence Cheuk/MIT
[129]Full Screen
* The Fermi gas microscope group: (from left) graduate students
Katherine Lawrence and Melih Okan, postdoc Thomas Lompe, graduate
student Matt Nichols, Professor Martin Zwierlein, and graduate
student Lawrence Cheuk.
The Fermi gas microscope group: (from left) graduate students
Katherine Lawrence and Melih Okan, postdoc Thomas Lompe, graduate
student Matt Nichols, Professor Martin Zwierlein, and graduate
student Lawrence Cheuk.
Photo: Jose-Luis Olivares/MIT
[130]Full Screen

Researchers build new fermion microscope

Laser beams are precisely aligned before being sent into the vacuum
chamber.

Instrument freezes and images 1,000 individual fermionic atoms at once.

Jennifer Chu | MIT News Office
May 13, 2015
[131]Press Inquiries [132]Share

Press Contact

Abby Abazorius
Email: [133]abbya@mit.edu
Phone: 617-253-2709
MIT News Office

Media Resources

5 images for download

[134]Access Media

Media can only be downloaded from the desktop version of this website.

Share

Comment

[135]Leave a comment

Fermions are the building blocks of matter, interacting in a multitude
of permutations to give rise to the elements of the periodic table.
Without fermions, the physical world would not exist.

Examples of fermions are electrons, protons, neutrons, quarks, and
atoms consisting of an odd number of these elementary particles.
Because of their fermionic nature, electrons and nuclear matter are
difficult to understand theoretically, so researchers are trying to use
ultracold gases of fermionic atoms as stand-ins for other fermions.

But atoms are extremely sensitive to light: When a single photon hits
an atom, it can knock the particle out of place — an effect that has
made imaging individual fermionic atoms devilishly hard.

Now a team of MIT physicists has built a microscope that is able to see
up to 1,000 individual fermionic atoms. The researchers devised a
laser-based technique to trap and freeze fermions in place, and image
the particles simultaneously.

The new imaging technique uses two laser beams trained on a cloud of
fermionic atoms in an optical lattice. The two beams, each of a
different wavelength, cool the cloud, causing individual fermions to
drop down an energy level, eventually bringing them to their lowest
energy states — cool and stable enough to stay in place. At the same
time, each fermion releases light, which is captured by the microscope
and used to image the fermion's exact position in the lattice — to an
accuracy better than the wavelength of light.

With the new technique, the researchers are able to cool and image over
95 percent of the fermionic atoms making up a cloud of potassium gas.
Martin Zwierlein, a professor of physics at MIT, says an intriguing
result from the technique appears to be that it can keep fermions cold
even after imaging.

"That means I know where they are, and I can maybe move them around
with a little tweezer to any location, and arrange them in any pattern
I'd like," Zwierlein says.

Zwierlein and his colleagues, including first author and graduate
student Lawrence Cheuk, have published their results today in the
journal Physical Review Letters.

Seeing fermions from bosons

For the past two decades, experimental physicists have studied
ultracold atomic gases of the two classes of particles: fermions and
bosons — particles such as photons that, unlike fermions, can occupy
the same quantum state in limitless numbers. In 2009, physicist Markus
Greiner at Harvard University devised a microscope that successfully
imaged individual bosons in a tightly spaced optical lattice. This
milestone was followed, in 2010, by a second boson microscope,
developed by Immanuel Bloch's group at the Max Planck Institute of
Quantum Optics.

These microscopes revealed, in unprecedented detail, the behavior of
bosons under strong interactions. However, no one had yet developed a
comparable microscope for fermionic atoms.

"We wanted to do what these groups had done for bosons, but for
fermions," Zwierlein says. "And it turned out it was much harder for
fermions, because the atoms we use are not so easily cooled. So we had
to find a new way to cool them while looking at them."

Techniques to cool atoms ever closer to absolute zero have been devised
in recent decades. Carl Wieman, Eric Cornell, and MIT's Wolfgang
Ketterle were able to achieve Bose-Einstein condensation in 1995, a
milestone for which they were awarded the 2001 Nobel Prize in physics.
Other techniques include a process using lasers to cool atoms from 300
degrees Celsius to a few ten-thousandths of a degree above absolute
zero.

A clever cooling technique

And yet, to see individual fermionic atoms, the particles need to be
cooled further still. To do this, Zwierlein's group created an optical
lattice using laser beams, forming a structure resembling an egg
carton, each well of which could potentially trap a single fermion.
Through various stages of laser cooling, magnetic trapping, and further
evaporative cooling of the gas, the atoms were prepared at temperatures
just above absolute zero — cold enough for individual fermions to
settle onto the underlying optical lattice. The team placed the lattice
a mere 7 microns from an imaging lens, through which they hoped to see
individual fermions.

However, seeing fermions requires shining light on them, causing a
photon to essentially knock a fermionic atom out of its well, and
potentially out of the system entirely.

"We needed a clever technique to keep the atoms cool while looking at
them," Zwierlein says.

His team decided to use a two-laser approach to further cool the atoms;
the technique manipulates an atom's particular energy level, or
vibrational energy. Each atom occupies a certain energy state — the
higher that state, the more active the particle is. The team shone two
laser beams of differing frequencies at the lattice. The difference in
frequencies corresponded to the energy between a fermion's energy
levels. As a result, when both beams were directed at a fermion, the
particle would absorb the smaller frequency, and emit a photon from the
larger-frequency beam, in turn dropping one energy level to a cooler,
more inert state. The lens above the lattice collects the emitted
photon, recording its precise position, and that of the fermion.

Zwierlein says such high-resolution imaging of more than 1,000
fermionic atoms simultaneously would enhance our understanding of the
behavior of other fermions in nature — particularly the behavior of
electrons. This knowledge may one day advance our understanding of
high-temperature superconductors, which enable lossless energy
transport, as well as quantum systems such as solid-state systems or
nuclear matter.

"The Fermi gas microscope, together with the ability to position atoms
at will, might be an important step toward the realization of a quantum
computer based on fermions," Zwierlein says. "One would thus harness
the power of the very same intricate quantum rules that so far hamper
our understanding of electronic systems."

Zwierlein says it is a good time for Fermi gas microscopists: Around
the same time his group first reported its results, teams from Harvard
and the University of Strathclyde in Glasgow also reported imaging
individual fermionic atoms in optical lattices, indicating a promising
future for such microscopes.

Zoran Hadzibabic, a professor of physics at Trinity College, says the
group's microscope is able to detect individual atoms "with almost
perfect fidelity."

"They detect them reliably, and do so without affecting their positions
— that's all you want," says Hadzibabic, who did not contribute to the
research. "So far they demonstrated the technique, but we know from the
experience with bosons that that's the hardest step, and I expect the
scientific results to start pouring out."

This research was funded in part by the National Science Foundation,
the Air Force Office of Scientific Research, the Office of Naval
Research, the Army Research Office, and the David and Lucile Packard
Foundation.
__________________________________________________________________


(... links deleted ...)

[181]Massachusetts Institute of Technology

[182]MIT News Office • [183]Building 11-400
[184]Massachusetts Institute of Technology • Cambridge, MA 02139-4307

[185]Back to the top

References

126. http://newsoffice.mit.edu/sites/mit.edu.newsoffice/files/images/2015/MIT-Fermion-1.jpg
127. http://newsoffice.mit.edu/sites/mit.edu.newsoffice/files/images/2015/MIT-Fermion-2.jpg
128. http://newsoffice.mit.edu/sites/mit.edu.newsoffice/files/images/2015/MIT-Fermion-3.jpg
129. http://newsoffice.mit.edu/sites/mit.edu.newsoffice/files/images/2015/MIT-Fermion-4.jpg
130. http://newsoffice.mit.edu/sites/mit.edu.newsoffice/files/images/2015/MIT-Fermion-5.jpg
131. http://newsoffice.mit.edu/2015/fermion-microscope-0513#press-inquiry-section
132. http://newsoffice.mit.edu/2015/fermion-microscope-0513#share-choices
133. mailto:abbya@mit.edu
134. http://newsoffice.mit.edu/media-download?article=31554
135. http://newsoffice.mit.edu/2015/fermion-microscope-0513#separator-comments

"Reprinted with permission of MIT News" (http://newsoffice.mit.edu/)
_______________________________________________
tt mailing list
tt@postbiota.org
http://postbiota.org/mailman/listinfo/tt