Friday, June 3, 2011

Not pear-shaped

FUNDAMENTAL building blocks of matter, like quarks (which make up the protons and neutrons in atomic nuclei) and electrons (which orbit those nuclei), are called point particles. This is somewhat misleading. It implies that although they have mass, they are also, like mathematical points, zero-dimensional—in other words, they do not take up any space. In the parlance of quantum mechanics, however, to call a particle pointlike is to say no more than that it is elementary, ie, that it is not known to be made up of smaller bits. Nowhere is it stipulated that it cannot have a shape.

Indeed, shape matters. Take the electron, the most manageable of all elementary particles, and thus the most thoroughly studied. According to the Standard Model, a 40-year-old theory which describes the behaviour of all the known elementary particles and forces of nature apart from gravity, an electron's point mass sits amid a cloud of virtual particles which pop in and out of existence—the sort of thing possible in the weird world of quantum mechanics. Theory suggests that this cloud should be an almost perfect sphere. The crucial word, though, is "almost".

A departure from Platonic perfection is predicted to be caused by the particle's electric dipole moment. Unfortunately, this has never been measured. That matters for two reasons. First, various versions of the Standard Model make different predictions about the size of the electric dipole moment. Measuring it would help choose between them. Second, many physicists believe the electron's electric dipole moment is a manifestation of the asymmetry that causes the universe to be made of matter.

If the world were completely symmetrical at a fundamental level, equal amounts of matter and antimatter would have been created in the Big Bang and would then have gone on to annihilate each other, with the result that the only thing left in the universe would be radiation. Moreover, this asymmetry implies that the laws of physics would be different if the arrow of time were reversed. This might be an explanation of what is (to a physicist, at least) a strange anomaly in the fabric of the universe, namely that it is possible to travel in any direction in the dimensions of space, but only one direction in the dimension of time. Measuring the electric dipole moment, then, is the sort of thing that really floats physicists' boats. The question is, how to do it?

Besides their putative electric dipole moment electrons have a real and measurable magnetic dipole moment. They act, in other words, like tiny bar magnets with north and south poles, making them rotate in a magnetic field. Any electric moment would arise if the particle's charge were distributed unevenly along the axis around which the particle spins in this way. The consequence would be that the particle's centre of charge and its centre of mass were not the same point, meaning it was not quite round.

A team of physicists at Imperial College, London, led by Edward Hinds, has spent the past ten years trying to see just how round the electron really is. The obvious way to go about this task is to send electrons through an electric field and see whether they twist and turn. Any electric dipole moment would align itself with the the electric field. Since the centre of mass is offset this would make the particles precess like gyroscopes. The stronger the field, and the longer an electron spent floating in it, the more visible any such wobbling would be.

Alas, a free electron carries an electric charge. This means that using a stronger field merely speeds it up, slinging it rapidly into the wall of the apparatus, and reducing the amount of time available for measurement. To make matters worse, an electron moving through an electric field generates its own magnetic field, which couples with its magnetic moment to cause a second, confounding precession.

So, instead of using electrons, Dr Hinds and his colleagues chose to work with molecules of ytterbium fluoride, a highly ionic substance. An electric field will not accelerate a neutral molecule in the way it would an electron, but it will polarise the strong ionic bond which holds the molecule together, separating the opposite charges and, in effect, isolating some of the electrons within it so that their spins can be studied.

After more than ten years of fiddling with their set-up, Dr Hines's team has succeeded in determining that the electron is round to within one part in a million billion. That will not confoud the theoreticians too much, but Dr Hines hopes to improve the accuracy of his measurements tenfold over the next few years, and eventually to achieve a hundredfold improvement. By then, any anomalies should be obvious. If they are not, then it is the theories of physics themselves that will have gone distinctly pear-shaped.

The end of AIDS?

Thirty years on, it looks as though the plague can now be beaten, if the world has the will to do so

ON JUNE 5th 1981 America’s Centres for Disease Control and Prevention reported the outbreak of an unusual form of pneumonia in Los Angeles. When, a few weeks later, its scientists noticed a similar cluster of a rare cancer called Kaposi’s sarcoma in San Francisco, they suspected that something strange and serious was afoot. That something was AIDS.

Since then, 25m people have died from AIDS and another 34m are infected. The 30th anniversary of the disease’s discovery has been taken by many as an occasion for hand-wringing. Yet the war on AIDS is going far better than anyone dared hope. A decade ago, half of the people in several southern African countries were expected to die of AIDS. Now, the death rate is dropping. In 2005 the disease killed 2.1m people. In 2009, the most recent year for which data are available, the number was 1.8m. Some 5m lives have already been saved by drug treatment. In 33 of the worst-affected countries the rate of new infections is down by 25% or more from its peak.

Even more hopeful is a recent study which suggests that the drugs used to treat AIDS may also stop its transmission (see article). If that proves true, the drugs could achieve much of what a vaccine would. The question for the world will no longer be whether it can wipe out the plague, but whether it is prepared to pay the price.

The appliance of science

If AIDS is defeated, it will be thanks to an alliance of science, activism and altruism. The science has come from the world’s pharmaceutical companies, which leapt on the problem. In 1996 a batch of similar drugs, all of them inhibiting the activity of one of the AIDS virus’s crucial enzymes, appeared almost simultaneously. The effect was miraculous, if you (or your government) could afford the $15,000 a year that those drugs cost when they first came on the market.

Much of the activism came from rich-world gays. Having badgered drug companies into creating the new medicines, the activists bullied them into dropping the price. That would have happened anyway, but activism made it happen faster.

The altruism was aroused as it became clear by the mid-1990s that AIDS was not just a rich-world disease. Three-quarters of those affected were—and still are—in Africa. Unlike most infections, which strike children and the elderly, AIDS hits the most productive members of society: businessmen, civil servants, engineers, teachers, doctors, nurses. Thanks to an enormous effort by Western philanthropists and some politicians (this is one area where even the left should give credit to George Bush junior), a series of programmes has brought drugs to those infected.

The result is patchy. Not enough people—some 6.6m of the 16m who would most quickly benefit—are getting the drugs. And the pills are not a cure. Stop taking them, and the virus bounces back. But it is a huge step forward from ten years ago.

What can science offer now? A few people’s immune systems control the disease naturally (which suggests a vaccine might be possible) and antibodies have been discovered that neutralise the virus (and might thus form the basis of AIDS-clearing drugs). But a cure still seems a long way off. Prevention is, for the moment, the better bet.

There are various ways to stop people getting the disease in the first place. Nagging them to use condoms and to sleep around less does have some effect. Circumcision helps to protect men. A vaginal microbicide (none exists, but at least one trial has gone well) could protect women. The new hope centres on the idea of combining treatment with prevention.

A question of money

In the early days scientists were often attacked by activists for being more concerned with trying to prevent the epidemic spreading than treating the affected. Now it seems that treatment and prevention will come in the same pill. If you can stop the virus reproducing in someone’s body, you not only save his life, you also reduce the number of viruses for him to pass on. Get enough people on drugs and it would be like vaccinating them: the chain of transmission would be broken.

That is a huge task. It is not just a matter of bringing in those who should already be on the drugs (the 16m who show symptoms or whose immune systems are critically weak). To prevent transmission, treatment would in theory need to be expanded to all the 34m people infected with the disease. That would mean more effective screening (which is planned already), and also a willingness by those without the symptoms to be treated. That willingness might be there, though, if it would protect people’s uninfected lovers.

Such a programme would take years and also cost a lot of money. About $16 billion a year is spent on AIDS in poor and middle-income countries. Half is generated locally and half is foreign aid. A report in this week’s Lancet suggests a carefully crafted mixture of approaches that does not involve treating all those without symptoms would bring great benefit for not much more than this—a peak of $22 billion in 2015, and a fall thereafter. Moreover, most of the extra spending would be offset by savings on the treatment of those who would have been infected, but were not—some 12m people, if the boffins have done their sums right. At $500 per person per year, the benefits would far outweigh the costs in purely economic terms; though donors will need to compare the gain from spending more on knocking out AIDS against other worthy causes, such as eliminating malaria (see article).

For the moment, the struggle is to stop some rich countries giving less. The Netherlands and Spain are cutting their contributions to the Global Fund, one of the two main distributors of the life-saving drugs (the other is Mr Bush’s brainchild, PEPFAR), and Italy has stopped paying altogether.

On June 8th the United Nations meets to discuss what to do next. Those who see the UN as a mere talking-shop should remember that its first meeting on AIDS launched the Global Fund. It is still a long haul. But AIDS can be beaten. A plague that 30 years ago was blamed on man’s iniquity has ended up showing him in a better, more inventive and generous light.

Slowing down in old age

A new way to measure the age of stars

TWO years into its mission, NASA’s planet-hunting Kepler space telescope has been a big success. With just four months of data, astronomers have found evidence for more than 1,200 planets circling stars other than the sun. That haul has more than doubled the number known, and suggests such planets are common. One estimate, extrapolating fromKepler’s data, is that there are as many as 50 billion planets in the Milky Way alone.

But Kepler—which detects its quarry by noting the minuscule dimming of starlight that occurs when a planet crosses in front of its parent star—can be used for other things, too. In a paper presented on May 23rd to the annual meeting of the American Astronomical Society, in Boston, a team led by Soren Meibom of Harvard University used data gathered by the telescope to give astronomers a better idea of how old the stars they study are.

Astronomers who study star clusters have noticed that the speed at which a star of a given mass spins (measured by tracking cool, dark spots on the surface) also seems to vary predictably with age. Young stars spin more quickly than old ones. If that relationship could be firmed up, it would offer a way to measure the age of isolated stars that are not part of clusters—a group that includes almost all the stars currently believed to host planets.At the moment, getting an accurate idea of stellar age is possible only in unusual circumstances—specifically, if a star is part of a cluster whose members formed from the same cloud of gas. The bigger a star is, the more rapidly it burns up its fuel, and the quicker it becomes a bloated red giant. Since all the stars in a cluster are roughly the same age it is possible, by looking at the masses of stars that have made it to the red giant stage, to calculate the age of the cluster and, consequently, of all its members.

That is easier said than done. The number of spots falls as a star ages. Combined with the difficulties of Earth-based astronomy, which requires that researchers peer through the murk of the atmosphere, that makes it hard to measure the spins of stars older than about 600m years—a tenth, or less, of the lifetime of a long-lived star. The only data point available for such multi-billion-year-old stars is a particular yellow dwarf in the Orion arm of the Milky Way. This star, which formed around 4.6 billion years ago and takes 26 days to complete one revolution, will be familiar to readers every sunrise.

But Kepler is good at finding spots on stars. It can distinguish them from planets because they are visible for half the time as a star rotates (a planet, by contrast, produces a short dip in stellar illumination). And thanks to its vantage point in space, the craft’s telescope can obtain much clearer images than Earth-based instruments. Dr Meibom’s paper (to be published soon in Astrophysical Journal Letters) looked at a cluster of stars that is roughly a billion years old, and found that the relationship between age and spin-speed was still tight.

In itself, that is but a small advance. Dr Meibom and his team are, however, in the process of studying a second cluster. This one is 2.5 billion years old. Further clusters within Kepler’s field of view are older still, so it should soon be clear whether the relationship continues to hold. If it does, that would have important implications forKepler’s main mission, which is to search for Earthlike planets. After all, one important feature of the Earth is its age, which has given time for complex life to evolve on its surface. For a planet to be truly Earthlike, how long it has been around might be one of its most important features.

Correction: Dr Meibom's paper is to be published in Astrophysical Journal Letters, notAstronomical Journal Letters as we originally wrote. This was corrected on May 31st 2011.

Inside the Infant Mind: Babies Can Perform Sophisticated Analyses of How the Physical World Should Behave

Science Daily — Over the past two decades, scientists have shown that babies only a few months old have a solid grasp on basic rules of the physical world. They understand that objects can't wink in and out of existence, and that objects can't "teleport" from one spot to another.

Baby playing. Scientists have found that infants can form surprisingly sophisticated expectations of how novel situations will unfold. And if something does not fit their expectations, an infants' level of surprise can be measured by how long they look at something: The more unexpected the event, the longer they watch. (Credit: © Galina Barskaya / Fotolia)

Furthermore, the scientists developed a computational model of infant cognition that accurately predicts infants' surprise at events that violate their conception of the physical world.Now, an international team of researchers co-led by MIT's Josh Tenenbaum has found that infants can use that knowledge to form surprisingly sophisticated expectations of how novel situations will unfold.

The model, which simulates a type of intelligence known as pure reasoning, calculates the probability of a particular event, given what it knows about how objects behave. The close correlation between the model's predictions and the infants' actual responses to such events suggests that infants reason in a similar way, says Tenenbaum, associate professor of cognitive science and computation at MIT.

"Real intelligence is about finding yourself in situations that you've never been in before but that have some abstract principles in common with your experience, and using that abstract knowledge to reason productively in the new situation," he says.

The study, which appears in the May 27 issue of Science, is the first step in a long-term effort to "reverse-engineer" infant cognition by studying babies at ages 3-, 6- and 12-months (and other key stages through the first two years of life) to map out what they know about the physical and social world. That "3-6-12" project is part of a larger Intelligence Initiative at MIT, launched this year with the goal of understanding the nature of intelligence and replicating it in machines.

Tenenbaum and Luca Bonatti of the Universitat Pompeu Fabra in Barcelona are co-senior authors of the Science paper; the co-lead authors are Erno Teglas of Central European University in Hungary and Edward Vul, a former MIT student who worked with Tenenbaum and is now at the University of California at San Diego.

Elizabeth Spelke, a professor of psychology at Harvard University, did much of the pioneering work showing that babies understand abstract principles about the physical world. Spelke also demonstrated that infants' level of surprise can be measured by how long they look at something: The more unexpected the event, the longer they watch.

Tenenbaum and Vul developed a computational model, known as an "ideal-observer model," to predict how long infants would look at animated scenarios that were more or less consistent with their knowledge of objects' behavior. The model starts with abstract principles of how objects can behave in general (the same principles that Spelke showed infants have), then runs multiple simulations of how objects could behave in a given situation.

In one example, 12-month-olds were shown four objects -- three blue, one red -- bouncing around a container. After some time, the scene would be covered, and during that time, one of the objects would exit the container through an opening.

If the scene was blocked very briefly (0.04 seconds), infants would be surprised if one of the objects farthest from the exit had left the container. If the scene was obscured longer (2 seconds), the distance from exit became less important and they were surprised only if the rare (red) object exited first. At intermediate times, both distance to the exit and number of objects mattered.

The computational model accurately predicted how long babies would look at the same exit event under a dozen different scenarios, varying number of objects, spatial position and time delay. This marks the first time that infant cognition has been modeled with such quantitative precision, and suggests that infants reason by mentally simulating possible scenarios and figuring out which outcome is most likely, based on a few physical principles.

"We don't yet have a unified theory of how cognition works, but we're starting to make progress on describing core aspects of cognition that previously were only described intuitively. Now we're describing them mathematically," Tenenbaum says.

In addition to performing similar studies with younger infants, Tenenbaum plans to further refine his model by adding other physical principles that babies appear to understand, such as gravity or friction. "We think infants are much smarter, in a sense, than this model is," he says. "We now need to do more experiments and model a broader range of the existing literature to test exactly what they know."

He is also developing similar models for infants' "intuitive psychology," or understanding of how other people act. Such models of normal infant cognition could help researchers figure out what goes wrong in disorders such as autism. "We have to understand more precisely what the normal case is like in order to understand how it breaks," Tenenbaum says.

The research was funded by the Ministerio de Ciencia E Innovación (Spain), the James S. McDonnell Foundation, the Office of Naval Research, the Army Research Office, and the Marie Curie Disorders and Coherence of the Embodied Self Research Training Network.

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Phase Change Memory-Based 'Moneta' System Points to the Future of Computer Storage

A view of the internals of the Moneta storage array with phase change memory modules installed. (Credit: UC San Diego / Steve Swanson)

Science Daily — A University of California, San Diego faculty-student team is about to demonstrate a first-of-its kind, phase-change memory solid state storage device that provides performance thousands of times faster than a conventional hard drive and up to seven times faster than current state-of-the-art solid-state drives (SSDs).

Moneta marks the latest advancement in solid state drives (SSDs). Unlike conventional hard disk drives, solid state storage drives have no moving parts. Today's SSDs use flash memory and can be found in a wide range of consumer electronics such as iPads and laptops. Although faster than hard disk, flash memory is still too slow to meet modern data storage and analysis demands, particularly in the area of high performance computing where the ability to sift through enormous volumes of data quickly is critical. Examples include storing and analyzing scientific data collected through environmental sensors, or even web searches through Google.The device was developed in the Computer Science and Engineering department at the UC San Diego Jacobs School of Engineering and will be on exhibit June 7-8 at DAC 2011, the world's leading technical conference and trade show on electronic design automation, with the support of several industry partners, including Micron Technology, BEEcube and Xilinx. The storage system, called "Moneta," uses phase-change memory (PCM), an emerging data storage technology that stores data in the crystal structure of a metal alloy called a chalcogenide. PCM is faster and simpler to use than flash memory -- the technology that currently dominates the SSD market.

"As a society, we can gather all this data very, very quickly -- much faster than we can analyze it with conventional, disk-based storage systems," said Steven Swanson, professor of Computer Science and Engineering and director of the Non-Volatile Systems Lab (NVSL). "Phase-change memory-based solid state storage devices will allow us to sift through all of this data, make sense of it, and extract useful information much faster. It has the potential to be revolutionary."

PCM Memory Chips

To store data, the PCM memory chips switch the alloy between a crystalline and amorphous state based on the application of heat through an electrical current. To read the data, the chips use a smaller current to determine which state the chalcogenide is in.

Moneta uses Micron Technology's first-generation PCM chips and can read large sections of data at a maximum rate of 1.1 gigabytes per second and write data at up to 371 megabytes per second. For smaller accesses (e.g., 512 B), Moneta can read at 327 megabytes per second and write at 91 megabytes per second , or between two and seven times faster than a state-of-the-art, flash-based SSD. Moneta also provides lower latency for each operation and should reduce energy requirements for data-intensive applications.

A Glimpse at Computers of the Future

Swanson hopes to build the second generation of the Moneta storage device in the next six to nine months and says the technology could be ready for market in just a few years as the underlying phase-change memory technology improves. The development has also revealed a new technology challenge.

"We've found that you can build a much faster storage device, but in order to really make use of it, you have to change the software that manages it as well. Storage systems have evolved over the last 40 years to cater to disks, and disks are very, very slow," said Swanson. "Designing storage systems that can fully leverage technologies like PCM requires rethinking almost every aspect of how a computer system's software manages and accesses storage. Moneta gives us a window into the future of what computer storage systems are going to look like, and gives us the opportunity now to rethink how we design computer systems in response."

In addition to Swanson, the Moneta team includes Computer Science and Engineering Professor and Chair Rajesh Gupta, who is also associate director of UC San Diego's California Institute for Telecommunications and Information Technology. Student team members from the Department of Computer Science and Engineering include Ameen Akel, Adrian Caulfield, Todor Mollov, Arup De, and Joel Coburn.

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கூட்டுமுயற்சியில் இணையம் வழியே வரைய ஓர் தளம்

கூட்டு முயற்சிக்கு கைகொடுப்பது,அதிலும் இந்த நொடியில் எங்கோ இருக்கும் நண்பர் அல்லது கூட்டாளியோடு இணைந்து செயல்பட உதவுவது என்பது இணையத்தின் தனிச்சிறப்பாக இருக்கிறது. பிரவுசரில் இப்போது நாம் பார்த்துக் கொண்டிருக்கும் இணைய பக்கத்தை நண்பர்களோடு பகிர்ந்து கொள்ள உதவும் சேவைகள் கூட உருவாக்கப் பட்டுள்ளன.

இத்தகைய கூட்டு முயற்சியின் அருமையையும் தேவையையும் உணர்ந்தவர்களுக்காக உதயமாகியுள்ள மற்றொரு இணைய சேவையாக கோஸ்கெட்ச் இணையதள‌த்தையும் குறிப்பிடலாம்.

கோஸ்கெட்ச் பெயருக்கு ஏற்பவே நண்பர்களோடு இணைந்து இணையம் வழியே வரைவதற்கான சேவையாகும்.நீங்கள் வரைந்துள்ள ஓவியத்தை நண்பர்களுக்கு காட்ட வேண்டும் என்றாலோ அல்லது சித்திரம் மூலம் புதிய யோசனையை மற்றவர்களோடு பகிர்ந்து கொள்ள நினைத்தாலோ இந்த சேவையை பயன்படுத்திக்கொள்ளலாம்.

வரைவது என்றவுடன் பிகாசோ போல ஓவிய நிபுணராக இருக்க வேண்டும் என்று நினைத்துவிடாதீர்கள்.ஒரு எண்ணம் அல்லது திட்டத்தை சித்திரமாக வரைந்து காட்ட வேண்டிய தேவை ஏற்படும் போது காகிதத்தில் எளிமையாக வரைந்து காட்டுவது போல இதில் வரைந்து காட்டலாம்.

இதற்கான எளிதான இணைய பென்சில்களும் வர்ணங்களும் கொடுக்கப்பட்டுள்ளன. அவற்றில் உங்களுக்கு தேவையானதை தேர்வு செய்து கொண்டு மனதில் உள்ளதை வரைந்து கொள்ளலாம்.இந்த பக்கத்தின் இணையமுகவரியை நண்பர்களுக்கு தெரிவித்தால் அவர்களும் அதே பக்கத்தை பார்க்க முடிவதோடு அதில் திருத்தங்களையோ மாற்றங்களையோ செய்யலாம்.

சும்மா ஜாலியாக வரைந்த சித்திரத்தை பகிர்ந்து கொள்ளவும் இந்த வ‌சதியை பயன்படுத்திக் கொள்ளலாம்.அல்லது நண்பர்களோடு இணைந்து துவக்க உள்ள புதிய நிறுவனம் அல்லது திட்டத்திற்கான வரைவு நகலையும் கூட இப்படி பகிர்ந்து கொள்ளலாம்.

இந்த சித்திரத்தை காணும் நண்பர்கள் அத‌னை மேம்படுத்துவதில் தங்களும் சேர்ந்து கொள்ளலாம் அல்லது தங்கள் கருத்துக்களை குறிப்பிடலாம்.இந்த வகையில் ஒரு மைய எண்ணத்தின் அடிப்படையில் நண்பர்கள் கூட்டாக செயல்பட்டு மாபெரும் திட்டத்தை உருவாக்கலாம்.

வரைவதற்கான இணைய கருவிகளோடு பல்வேறு வகையான உருவங்கள் போன்ற‌வற்றை யன்படுத்திக்கொள்ளும் வசதியும் இருக்கிற‌து.உதாரணமாக சித்திரக் கதை தோற்ற‌ங்களையோ அல்லது விளையாட்டு பொருட்களின் உருவத்தையோ பயன்படுத்தலாம். இதே போல குறிப்பிட்ட புகைப்படத்தையும் பயன்படுத்தலாம்.

ஏற்கனவோ சொன்னது போல ஒரு நல்ல எண்ணத்தை அல்லது ஒரு பிரச்ச‌னையை இதன் மூலம் பகிர்ந்து கொள்ளலாம்.இல்லை என்றால் பார்த்து ரசித்த ஒரு புகைப்படத்தை கூட நண்பர்களோடு பகிர்ந்து கொள்ளலாம்.நாம் உருவாக்கியவற்றை சேமித்து வைத்து கொண்டு எதிர்காலத்தில் பயன்படுத்திக் கொள்ளலாம்.அல்லது பேஸ்புக் மற்றும் வலைப் பதிவுகளிலும் இடம்பெற வைக்கலாம்.

புகைப்படங்களை தோன்ற செய்து பகிர்வது போல கூகுல் வரைப்படத்தையும் பகிர்ந்து கொள்ளும் வசதி இருக்கிறது.குறிப்பிட்ட இடத்தை சுட்டிக்காட்ட இந்த வசதியை பயன்படுத்திக்கொள்ளலாம்.

எல்லா உலாவிகளிலும் செயல்படும் என்பதும் தனியே பதிவு செய்து கொள்ள தேவையில்லை என்பதும் இந்த சேவையை மேலும் பயனுள்ள தாக்குகிற‌து.

http://www.cosketch.com/ என்ற தளத்திற்கு சென்று பாருங்கள்