Searching for Spin Liquids: Much-Sought Exotic Quantum State of Matter Can Exist

The world economy is becoming ever more reliant on high tech electronics such as computers featuring fingernail-sized microprocessors crammed with billions of transistors. For progress to continue, for Moore's Law -- according to which the number of computer components crammed onto microchips doubles every two years, even as the size and cost of components halves -- to continue, new materials and new phenomena need to be discovered.Diagram depicting anti-ferromagnetic order (upper) compared to a spin liquid phase (lower). In an anti-ferromagnet, the spins are anti-aligned. A spin liquid has no order and the spins can be viewed as bobbing about like water molecules in liquid water. (Credit: E. Edwards)
Furthermore, as the sizes of electronic components shrink, soon down to the size of single atoms or molecules, quantum interactions become ever more important. Consequently, enhanced knowledge and exploitation of quantum effects is essential. Researchers at the Joint Quantum Institute (JQI) in College Park, Maryland, operated by the University of Maryland and the National Institute of Standards and Technology (NIST), and at Georgetown University have uncovered evidence for a long-sought-after quantum state of matter, a spin liquid.

The research was performed by JQI postdoctoral scientists Christopher Varney and Kai Sun, JQI Fellow Victor Galitski, and Marcos Rigol of Georgetown University. The results appear in an editor-recommended article in the 12 August issue of the journal Physical Review Letters.

You can't pour a spin liquid into a glass. It's not a material at all, at least not a material you can touch. It is more like a kind of magnetic disorder within an ordered array of atoms. Nevertheless, it has many physicists excited.

To understand this exotic state of matter, first consider the concept of spin, which is at the heart of all magnetic phenomena. For instance, a refrigerator magnet, at the microscopic level, consists of trillions of trillions of iron atoms all lined up. Each of these atoms can be thought of loosely as a tiny spinning ball. The orientation of that spin is what makes the atom into a tiny magnet. The refrigerator magnet is an example of a ferromagnet, the ferro part coming from the Latin word for iron. In a ferromagnet, all the atomic spins are lined up in the same way, producing a large cooperative magnetic effect.

Important though they may be, ferromagnets aren't the only kind of material where magnetic interactions between spins are critical. In anti-ferromagnets, for instance, the neighboring spins are driven to be anti-aligned. That is, the orientations of the spins alternate up and down (see top picture in figure). The accumulative magnetic effect of all these up and down spins is that the material has no net magnetism. The high-temperature superconducting materials discovered in the 1980s are an important example of an anti-ferromagnetic structure.

More complicated and potentially interesting magnetic arrangements are possible, which may lead to a quantum spin liquid. Imagine an equilateral triangle, with an atom (spin) at each corner. Anti-ferromagnetism in such a geometry would meet with difficulties. Suppose that one spin points up while a second spin points down. So far, so good. But what spin orientation can the third atom take? It can't simultaneously anti-align with both of the other atoms in the triangle. Physicists employ the word "frustration" to describe this baffling condition where all demands cannot be satisfied.

In everyday life frustration is, well, frustrating, and actually this condition is found throughout nature, from magnetism to neural networks. Furthermore, understanding the different manifestations of a collection of magnetically interacting spins might help in designing new types of electronic circuitry.

One compromise that a frustrated spin system makes is to simultaneously exist in many spin orientations. In a quantum system, this simultaneous existence, or superposition, is allowed.

Here's where the JQI researchers have tried something new. They have studied what happens when frustration occurs in materials with a hexagonal (six sided) unit cell lattice.

What these atoms do is interact via their respective spins. The strength of the interaction between nearest neighbor (NN) atoms is denoted by the parameter J1. Similarly, the force between next nearest neighbors (NNN) -- that is, pairs of atoms that have at least one intervening atom between them -- is denoted by J2. Letting this batch of atoms interact among themselves, even on a pretend lattice as small as this, entails an immense calculation. Varney and his colleagues have calculated what happens in an array of hexagons consisting of 30 sites where the spins are free to swing about in a two-dimensional plane (this kind of approach is called an XY model).

Christopher Varney, who has appointments at Maryland and Georgetown, said that the interactions of atoms can be represented by a matrix (essentially a two-dimensional spreadsheet) with 155 million entries on each side. This huge number corresponds to the different spin configurations that can occur on this honeycomb-structured material.

What the researchers found were a "kaleidoscope" of phases, which represent the lowest-energy states that are allowed given the magnetic interactions. Just as water can exist in different phases -- steam, liquid, and ice -- as the temperature is changed, so here a change in the strengths of the interactions among the spins (the J1 and J2 parameters) results in different phases. For example, one simple solution is an antiferromagnet (upper picture in figure).

But one phase turns out to be a true quantum spin liquid having no order at all. When J2 is between about 21% and 36% of the value of J1, frustration coaxes the spins into disorder; the entire sample co-exists in millions of quantum states simultaneously.

It's difficult for the human mind to picture a tiny two-dimensional material in so many states at the same time. JQI fellow, Victor Galitski, suggests that one shouldn't think of the spins as residing at the original atomic sites but rather as free ranging particle-like entities dubbed "spinons." These spinons bob about, just as water molecules bob about in liquid water (see lower picture in figure). Hence the name quantum spin liquid.

Another reason for using the word liquid, Galitski says, is this 'bobbing about' is analogous to what happens inside a metal. There, the outer electrons of most atoms tend to leave their home atoms and drift through the metal sample as if they constituted a fluid, called a "Fermi liquid."

Electrons in a metal are able to drift since it takes only an infinitesimal amount of energy to put them into motion. The same is true for the fluctuating spins in the hexagonal model studied by the JQI scientists. Indeed, their spin model assumes a temperature of absolute zero, where quantum effects abound.

Writing in an essay that accompanied the article in Physical Review Letters, Tameem Albash and Stephan Haas, scientists at the University of Southern California, say that the JQI/Georgetown team "present a convincing example" of the new spin liquid state.

How can this new frustration calculation be tested? The experimental verification of the spin liquid state in a 2-dimenstional hexagonal lattice, Albash and Haas suggest, "will probably be tested using cold atoms trapped in optical lattices. In the past few years, this technology has become a reliable tool to emulate quantum many body lattice systems with tunable interactions." Indeed the authors propose such an experiment.

What would such a spin liquid material be good for? It's too early to tell. But some speculations include the idea that these materials could support some exotic kind of superconductivity or would organize particle-like entities that possessed fractional electric charge.

"Kaleidoscope of Exotic Quantum Phases in a Frustrated XY Model" by Christopher N. Varney, Kai Sun, Victor Galitski, and Marcos Rigol, Physical Review Letters, 107, 077201, (12 August 2011).

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Engineers Solve Longstanding Problem in Photonic Chip Technology: Findings Help Pave Way for Next Generation of Computer Chips

Stretching for thousands of miles beneath oceans, optical fibers now connect every continent except for Antarctica. With less data loss and higher bandwidth, optical-fiber technology allows information to zip around the world, bringing pictures, video, and other data from every corner of the globe to your computer in a split second. But although optical fibers are increasingly replacing copper wires, carrying information via photons instead of electrons, today's computer technology still relies on electronic chips.Caltech engineers have developed a new way to 
isolate light on a photonic chip, allowing light to 
travel in only one direction. This finding can lead 
to the next generation of computer-chip technology: 
photonic chips that allow for faster computers 
and less data loss. (Credit: Caltech/Liang Feng)
Now, researchers led by engineers at the California Institute of Technology (Caltech) are paving the way for the next generation of computer-chip technology: photonic chips. With integrated circuits that use light instead of electricity, photonic chips will allow for faster computers and less data loss when connected to the global fiber-optic network.

"We want to take everything on an electronic chip and reproduce it on a photonic chip," says Liang Feng, a postdoctoral scholar in electrical engineering and the lead author on a paper to be published in the August 5 issue of the journal Science. Feng is part of Caltech's nanofabrication group, led by Axel Scherer, Bernard A. Neches Professor of Electrical Engineering, Applied Physics, and Physics, and co-director of the Kavli Nanoscience Institute at Caltech.

In that paper, the researchers describe a new technique to isolate light signals on a silicon chip, solving a longstanding problem in engineering photonic chips.

An isolated light signal can only travel in one direction. If light weren't isolated, signals sent and received between different components on a photonic circuit could interfere with one another, causing the chip to become unstable. In an electrical circuit, a device called a diode isolates electrical signals by allowing current to travel in one direction but not the other. The goal, then, is to create the photonic analog of a diode, a device called an optical isolator. "This is something scientists have been pursuing for 20 years," Feng says.

Normally, a light beam has exactly the same properties when it moves forward as when it's reflected backward. "If you can see me, then I can see you," he says. In order to isolate light, its properties need to somehow change when going in the opposite direction. An optical isolator can then block light that has these changed properties, which allows light signals to travel only in one direction between devices on a chip.

"We want to build something where you can see me, but I can't see you," Feng explains. "That means there's no signal from your side to me. The device on my side is isolated; it won't be affected by my surroundings, so the functionality of my device will be stable."

To isolate light, Feng and his colleagues designed a new type of optical waveguide, a 0.8-micron-wide silicon device that channels light. The waveguide allows light to go in one direction but changes the mode of the light when it travels in the opposite direction.

A light wave's mode corresponds to the pattern of the electromagnetic field lines that make up the wave. In the researchers' new waveguide, the light travels in a symmetric mode in one direction, but changes to an asymmetric mode in the other. Because different light modes can't interact with one another, the two beams of light thus pass through each other.

Previously, there were two main ways to achieve this kind of optical isolation. The first way -- developed almost a century ago -- is to use a magnetic field. The magnetic field changes the polarization of light -- the orientation of the light's electric-field lines -- when it travels in the opposite direction, so that the light going one way can't interfere with the light going the other way. "The problem is, you can't put a large magnetic field next to a computer," Feng says. "It's not healthy."

The second conventional method requires so-called nonlinear optical materials, which change light's frequency rather than its polarization. This technique was developed about 50 years ago, but is problematic because silicon, the material that's the basis for the integrated circuit, is a linear material. If computers were to use optical isolators made out of nonlinear materials, silicon would have to be replaced, which would require revamping all of computer technology. But with their new silicon waveguides, the researchers have become the first to isolate light with a linear material.

Although this work is just a proof-of-principle experiment, the researchers are already building an optical isolator that can be integrated onto a silicon chip. An optical isolator is essential for building the integrated, nanoscale photonic devices and components that will enable future integrated information systems on a chip. Current, state-of-the-art photonic chips operate at 10 gigabits per second (Gbps) -- hundreds of times the data-transfer rates of today's personal computers -- with the next generation expected to soon hit 40 Gbps. But without built-in optical isolators, those chips are much simpler than their electronic counterparts and are not yet ready for the market. Optical isolators like those based on the researchers' designs will therefore be crucial for commercially viable photonic chips.

In addition to Feng and Scherer, the other authors on the Science paper, "Non-reciprocal light propagation in a silicon photonic circuit," are Jingqing Huang, a Caltech graduate student; Maurice Ayache of UC San Diego and Yeshaiahu Fainman, Cymer Professor in Advanced Optical Technologies at UC San Diego; and Ye-Long Xu, Ming-Hui Lu, and Yan-Feng Chen of the Nanjing National Laboratory of Microstructures in China. This research was done as part of the Center for Integrated Access Networks (CIAN), one of the National Science Foundation's Engineering Research Centers. Fainman is also the deputy director of CIAN. Funding was provided by the National Science Foundation, and the Defense Advanced Research Projects Agency.

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Scientists Have New Help Finding Their Way Around Brain's Nooks and Crannies

Like explorers mapping a new planet, scientists probing the brain need every type of landmark they can get. Each mountain, river or forest helps scientists find their way through the intricacies of the human brain.Scientists have found a way to use MRI scanning data 
to map myelin, a white sheath that covers some brain 
cell branches. Such maps, previously only available via 
dissection, help scientists determine precisely where they 
are at in the brain. Red and yellow indicate regions with 
high myelin levels; blue, purple and black areas have low 
myelin levels. (Credit: David Van Essen)
Researchers at Washington University School of Medicine in St. Louis have developed a new technique that provides rapid access to brain landmarks formerly only available at autopsy. Better brain maps will result, speeding efforts to understand how the healthy brain works and potentially aiding in future diagnosis and treatment of brain disorders, the researchers report in the Journal of Neuroscience Aug. 10.

The technique makes it possible for scientists to map myelination, or the degree to which branches of brain cells are covered by a white sheath known as myelin in order to speed up long-distance signaling. It was developed in part through the Human Connectome Project, a $30 million, five-year effort to map the brain's wiring. That project is headed by Washington University in St. Louis and the University of Minnesota.

"The brain is among the most complex structures known, with approximately 90 billion neurons transmitting information across 150 trillion connections," says David Van Essen, PhD, Edison Professor and head of the Department of Anatomy and Neurobiology at Washington University. "New perspectives are very helpful for understanding this complexity, and myelin maps will give us important insights into where certain parts of the brain end and others begin."

Easy access to detailed maps of myelination in humans and animals also will aid efforts to understand how the brain evolved and how it works, according to Van Essen.

Neuroscientists have known for more than a century that myelination levels differ throughout the cerebral cortex, the gray outer layer of the brain where most higher mental functions take place. Until now, though, the only way they could map these differences in detail was to remove the brain after death, slice it and stain it for myelin.

Washington University graduate student Matthew Glasser developed the new technique, which combines data from two types of magnetic resonance imaging (MRI) scans that have been available for years.

"These are standard ways of imaging brain anatomy that scientists and clinicians have used for a long time," Glasser says. "After developing the new technique, we applied it in a detailed analysis of archived brain scans from healthy adults."

As in prior studies, Glasser's results show highest myelination levels in areas involved with early processing of information from the eyes and other sensory organs and control of movement. Many brain cells are packed into these regions, but the connections among the cells are less complex. Scientists suspect that these brain regions rely heavily on what computer scientists call parallel processing: Instead of every cell in the region working together on a single complex problem, multiple separate teams of cells work simultaneously on different parts of the problem.

Areas with less myelin include brain regions linked to speech, reasoning and use of tools. These regions have brain cells that are packed less densely, because individual cells are larger and have more complex connections with neighboring cells.

"It's been widely hypothesized that each chunk of the cerebral cortex is made up of very uniform information-processing machinery," Van Essen says. "But we're now adding to a picture of striking regional differences that are important for understanding how the brain works."

According to Van Essen, the technique will make it possible for the Connectome project to rapidly map myelination in many different research participants. Data on many subjects, acquired through many different analytical techniques including myelination mapping, will help the resulting maps cover the range of anatomic variation present in humans.

"Our colleagues are clamoring to make use of this approach because it's so helpful for figuring out where you are in the cortex, and the data are either already there or can be obtained in less than 10 minutes of MRI scanning," Glasser says.

This research was funded by the National Institutes of Health (NIH).

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Inexpensive catalyst that makes hydrogen gas 10 times faster than natural enzyme

Looking to nature for their muse, researchers have used a common protein to guide the design of a material that can make energy-storing hydrogen gas. The synthetic material works 10 times faster than the original protein found in water-dwelling microbes, the researchers report in the August 12 issue of the journal Science, clocking in at 100,000 molecules of hydrogen gas every second.The part of the catalyst that cranks out 100,000
molecules of hydrogen gas a second packs electrons
into chemical bonds between hydrogen atoms, possibly
hijacked from water. Credit: PNNL
This step is just one part of a series of reactions to split water and make hydrogen gas, but the researchers say the result shows they can learn from nature how to control those reactions to make durable synthetic catalysts for energy storage, such as in fuel cells.

In addition, the natural protein, an enzyme, uses inexpensive, abundant metals in its design, which the team copied. Currently, these materials -- called catalysts, because they spur reactions along -- rely on expensive metals such as platinum.

"This nickel-based catalyst is really very fast," said coauthor Morris Bullock of the Department of Energy's Pacific Northwest National Laboratory. "It's about a hundred times faster than the previous catalyst record holder. And from nature, we knew it could be done with abundant and inexpensive nickel or iron."

Stuffing Bonds

Electrical energy is nothing more than electrons. These same electrons are what tie atoms together when they are chemically bound to each other in molecules such as hydrogen gas. Stuffing electrons into chemical bonds is one way to store electrical energy, which is particularly important for renewable, sustainable energy sources like solar or wind power. Converting the chemical bonds back into flowing electricity when the sun isn't shining or the wind isn't blowing allows the use of the stored energy, such as in a fuel cell that runs on hydrogen.

Electrons are often stored in batteries, but Bullock and his colleagues want to take advantage of the closer packing available in chemicals.

"We want to store energy as densely as possible. Chemical bonds can store a huge amount of energy in a small amount of physical space," said Bullock, director of the Center for Molecular Electrocatalysis at PNNL, one of DOE's Energy Frontier Research Centers. The team also included visiting researcher Monte Helm from Fort Lewis College in Durango, Colo.

Biology stores energy densely all the time. Plants use photosynthesis to store the sun's energy in chemical bonds, which people use when they eat food. And a common microbe stores energy in the bonds of hydrogen gas with the help of a protein called a hydrogenase.

Because the hydrogenases found in nature don't last as long as ones that are built out of tougher chemicals (think paper versus plastic), the researchers wanted to pull out the active portion of the biological hydrogenase and redesign it with a stable chemical backbone.

Two Plus Two Equals One

In this study, the researchers looked at only one small part of splitting water into hydrogen gas, like fast-forwarding to the end of a movie. Of the many steps, there's a part at the end when the catalyst has a hold of two hydrogen atoms that it has stolen from water and snaps the two together.

The catalyst does this by completely dismantling some hydrogen atoms from a source such as water and moving the pieces around. Due to the simplicity of hydrogen atoms, those pieces are positively charged protons and negatively charged electrons. The catalyst arranges those pieces into just the right position so they can be put together correctly. "Two protons plus two electrons equals one molecule of hydrogen gas," says Bullock.

In real life, the protons would come from water, but since the team only examined a portion of the reaction, the researchers used water stand-ins such as acids to test their catalyst.

"We looked at the hydrogenase and asked what is the important part of this?" said Bullock. "The hydrogenase moves the protons around in what we call a proton relay. Where the protons go, the electrons will follow."

A Bauble for Energy

Based on the hydrogenase's proton relay, the experimental catalyst contained regions that dangled off the main structure and attracted protons, called "pendant amines." A pendant amine moves a proton into position on the edge of the catalyst, while a nickel atom in the middle of the catalyst offers a hydrogen atom with an extra electron (that's a proton and two electrons for those counting).

The pendant amine's proton is positive, while the nickel atom is holding on to a negatively charged hydrogen. Positioned close to each other, the opposites attract and the conglomerate solidifies into a molecule, forming hydrogen gas.

With that plan in mind, the team built potential catalysts and tested them. On their first try, they put a bunch of pendant amines around the nickel center, thinking more would be better. Testing their catalyst, they found it didn't work very fast. An analysis of how the catalyst was moving protons and electrons around suggested too many pendant amines got in the way of the perfect reaction. An overabundance of protons made for a sticky catalyst, which pinched it and slowed the hydrogen-gas-forming reaction down.

Like good gardeners, the team trimmed a few pendant amines off their catalyst, leaving only enough to make the protons stand out, ready to accept a negatively charged hydrogen atom.

Fastest Cat in the West

Testing the trimmed catalyst, the team found it performed much better than anticipated. At first they used conditions in which no water was present (remember, they used water stand-ins), and the catalyst could create hydrogen gas at a rate of about 33,000 molecules per second. That's much faster than their natural inspiration, which clocks in at around 10,000 per second.

However, most real-life applications will have water around, so they added water to the reaction to see how it would perform. The catalyst ran three times as fast, creating more than 100,000 hydrogen molecules every second. The researchers think the water might help by moving protons to a more advantageous spot on the pendant amine, but they are still studying the details.

Their catalyst has a drawback, however. It's fast, but it's not efficient. The catalyst runs on electricity -- after all, it needs those electrons to stuff into the chemical bonds -- but it requires more electricity than practical, a characteristic called the overpotential.

Bullock says the team has some ideas on how to reduce the inefficiency. Also, future work will require assembling a catalyst that splits water in addition to making hydrogen gas. Even with a high overpotential, the researchers see high potential for this catalyst.

More information: Monte L. Helm, Michael P. Stewart, R. Morris Bullock, M. Rakowski DuBois, Daniel L. DuBois, A Synthetic Nickel Electrocatalyst With a Turnover Frequency Above 100,000 s-1 for H2 Production, Science, August 12, 2011, DOI:10.1126/science.1205864

Provided by Pacific Northwest National Laboratory

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How Many Species On Earth? About 8.7 Million, New Estimate Says

Eight million, seven hundred thousand species (give or take 1.3 million).
Distribution of species by kingdom. (Credit: CoML)
That is a new, estimated total number of species on Earth -- the most precise calculation ever offered -- with 6.5 million species found on land and 2.2 million (about 25 percent of the total) dwelling in the ocean depths.

Announced today by Census of Marine Life scientists, the figure is based on an innovative, validated analytical technique that dramatically narrows the range of previous estimates. Until now, the number of species on Earth was said to fall somewhere between 3 million and 100 million.

Furthermore, the study, published by PLoS Biology, says a staggering 86% of all species on land and 91% of those in the seas have yet to be discovered, described and catalogued.

Says lead author Camilo Mora of the University of Hawaii and Dalhousie University in Halifax, Canada: "The question of how many species exist has intrigued scientists for centuries and the answer, coupled with research by others into species' distribution and abundance, is particularly important now because a host of human activities and influences are accelerating the rate of extinctions. Many species may vanish before we even know of their existence, of their unique niche and function in ecosystems, and of their potential contribution to improved human well-being."

"This work deduces the most basic number needed to describe our living biosphere," says co-author Boris Worm of Dalhousie University. "If we did not know -- even by an order of magnitude (1 million? 10 million? 100 million?) -- the number of people in a nation, how would we plan for the future?"

"It is the same with biodiversity. Humanity has committed itself to saving species from extinction, but until now we have had little real idea of even how many there are."

Dr. Worm notes that the recently-updated Red List issued by the International Union for the Conservation of Nature assessed 59,508 species, of which 19,625 are classified as threatened. This means the IUCN Red List, the most sophisticated ongoing study of its kind, monitors less than 1% of world species.

The research is published alongside a commentary by Lord Robert May of Oxford, past-president of the UK's Royal Society, who praises the researchers' "imaginative new approach."

"It is a remarkable testament to humanity's narcissism that we know the number of books in the US Library of Congress on 1 February 2011 was 22,194,656, but cannot tell you -- to within an order-of-magnitude -- how many distinct species of plants and animals we share our world with," Lord May writes.

"(W)e increasingly recognize that such knowledge is important for full understanding of the ecological and evolutionary processes which created, and which are struggling to maintain, the diverse biological riches we are heir to. Such biodiversity is much more than beauty and wonder, important though that is. It also underpins ecosystem services that -- although not counted in conventional GDP -- humanity is dependent upon."

Drawing conclusions from 253 years of taxonomy since Linnaeus

Swedish scientist Carl Linnaeus created and published in 1758 the system still used to formally name and describe species. In the 253 years since, about 1.25 million species -- roughly 1 million on land and 250,000 in the oceans -- have been described and entered into central databases (roughly 700,000 more are thought to have been described but have yet to reach the central databases).

To now, the best approximation of Earth's species total was based on the educated guesses and opinions of experts, who variously pegged the figure in a range from 3 to 100 million -- wildly differing numbers questioned because there is no way to validate them.

Drs. Mora and Worm, together with Dalhousie colleagues Derek P. Tittensor, Sina Adl and Alastair G.B. Simpson, refined the estimated species total to 8.7 million by identifying numerical patterns within the taxonomic classification system (which groups forms of life in a pyramid-like hierarchy, ranked upwards from species to genus, family, order, class, phylum, kingdom and domain).

Analyzing the taxonomic clustering of the 1.2 million species today in the Catalogue of Life and the World Register of Marine Species, the researchers discovered reliable numerical relationships between the more complete higher taxonomic levels and the species level.

Says Dr. Adl: "We discovered that, using numbers from the higher taxonomic groups, we can predict the number of species. The approach accurately predicted the number of species in several well-studied groups such as mammals, fishes and birds, providing confidence in the method."

When applied to all five known eukaryote* kingdoms of life on Earth, the approach predicted:
~7.77 million species of animals (of which 953,434 have been described and cataloged)~298,000 species of plants (of which 215,644 have been described and cataloged)~611,000 species of fungi (moulds, mushrooms) (of which 43,271 have been described and cataloged)~36,400 species of protozoa (single-cell organisms with animal-like behavior, eg. movement, of which 8,118 have been described and cataloged)~27,500 species of chromista (including, eg. brown algae, diatoms, water moulds, of which 13,033 have been described and cataloged)
Total: 8.74 million eukaryote species on Earth.

(* Notes: Organisms in the eukaryote domain have cells containing complex structures enclosed within membranes. The study looked only at forms of life accorded, or potentially accorded, the status of "species" by scientists. Not included: certain micro-organisms and virus "types," for example, which could be highly numerous.)

Within the 8.74 million total is an estimated 2.2 million (plus or minus 180,000) marine species of all kinds, about 250,000 (11%) of which have been described and catalogued. When it formally concluded in October 2010, the Census of Marine Life offered a conservative estimate of 1 million+ species in the seas.

"Like astronomers, marine scientists are using sophisticated new tools and techniques to peer into places never seen before," says Australian Ian Poiner, Chair of the Census' Scientific Steering Committee. "During the 10-year Census, hundreds of marine explorers had the unique human experience and privilege of encountering and naming animals new to science. We may clearly enjoy the Age of Discovery for many years to come."

"The immense effort entering all known species in taxonomic databases such as the Catalogue of Life and the World Register of Marine Species makes our analysis possible," says co-author Derek Tittensor, who also works with Microsoft Research and the UN Environment Programme's World Conservation Monitoring Centre. "As these databases grow and improve, our method can be refined and updated to provide an even more precise estimate."

"We have only begun to uncover the tremendous variety of life around us," says co-author Alastair Simpson. "The richest environments for prospecting new species are thought to be coral reefs, seafloor mud and moist tropical soils. But smaller life forms are not well known anywhere. Some unknown species are living in our own backyards -- literally."

"Awaiting our discovery are a half million fungi and moulds whose relatives gave humanity bread and cheese," says Jesse Ausubel, Vice-President of the Alfred P. Sloan Foundation and co-founder of the Census of Marine Life. "For species discovery, the 21st century may be a fungal century!"

Mr. Ausubel notes the enigma of why so much diversity exists, saying the answer may lie in the notions that nature fills every niche, and that rare species are poised to benefit from a change of conditions.

In his analysis, Lord May says the practical benefits of taxonomic discovery are many, citing the development in the 1970s of a new strain of rice based on a cross between conventional species and one discovered in the wild. The result: 30% more grain yield, followed by efforts ever since to protect all wild varieties of rice, "which obviously can only be done if we have the appropriate taxonomic knowledge."

"Given the looming problems of feeding a still-growing world population, the potential benefits of ramping up such exploration are clear."

Based on current costs and requirements, the study suggests that describing all remaining species using traditional approaches could require up to 1,200 years of work by more than 300,000 taxonomists at an approximate cost of $US 364 billion. Fortunately, new techniques such as DNA barcoding are radically reducing the cost and time involved in new species identification.

Concludes Dr. Mora: "With the clock of extinction now ticking faster for many species, I believe speeding the inventory of Earth's species merits high scientific and societal priority. Renewed interest in further exploration and taxonomy could allow us to fully answer this most basic question: What lives on Earth?"

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How Vampire Bats Find Veins

Heat-sensing protein channels in vampire bats allow the flying mammals to find the best place to sink their teeth into their prey.
Researchers have discovered an infrared-sensing protein channel that allows vampire bats to identify the hottest part of the animal—veins close to the skin’s surface that carry 38 degree-Celsius (100° F) blood, and presumably the best spot for feeding.

The channel is a variant of TRPV1, a heat-sensing protein channel that is triggered by high temperatures that could potentially cause injury, according to the study published today (August 3) in Nature, and is distinct from the heat sensor used by snakes—the only other non-insect animals that are known to detect heat by sensing infrared radiation.

“Infrared [detection] allows these guys, in pitch black, to hunt down warm-blooded prey,” said zoologist Bill Schutt, assistant professor at Long Island University, who was not involved in the research. Here, the researchers identified a modification in a common heat-sensing protein channel that lowered its temperature threshold so that it is more attuned to an animal’s body heat, he added.

The common vampire bat was appropriately named after the myth of Dracula—it feeds at night and lives solely on a diet of blood, every day or two consuming up to half its weight in the vital substance from large mammals, especially sleeping livestock. The bats first use echolocation to detect their prey, but once they are within 20 centimeters of their target, they use infrared sensors in specialized pits around their noses to zero in on the best place to feed.

In a previous study, physiologist David Julius at the University of California, San Francisco, and colleagues found that infrared detection by snakes—which, like bats, use nerves located in facial pits to detect their prey—is mediated by a cell-surface protein channel called transient receptor potential cation channel A1 (TRPA1). The channel is actually insensitive to heat in most organisms, but had evolved the capability in snakes, leading the group to suspect that a similar transformation may have given vampire bats their ability to sense infrared.

To see if this was the case, Julius and his collaborators at the University of California, San Francisco, the Venezuelan Institute of Scientific Investigation (IVIC), and the Carnegie Institution in Baltimore, Maryland, compared gene expression in vampire bats’ heat-sensing nerves, called trigeminal ganglia, with expression in a nerve cluster near the spine, called dorsal root ganglia (DRG). They also compared these expression patterns to those of the ganglia in four bat species that do not have infrared sensory abilities.

To their surprise, they did not observe any differences in transcription of the TRPA1-coding gene, nor of any other genes. Instead, they discovered that the protein TRPV1—a heat-sensing protein channel normally triggered by temperatures over 43° C (110° F)—existed in two different isoforms—an approximately 850-amino-acid version and one that was 62 amino acids shorter. The short form, which resulted from alternative splicing of the transcribed mRNA, made up as much as half of the TRPV1 found in the trigeminal ganglia of vampire bats, whereas it comprised only a small percentage of the TRPV1 in the DRG. It was similarly low in both types of nerve clusters in the other bat species, suggesting that the short form may play a role in infrared detection.

To test this hypothesis, the researchers expressed one of the two TRPV1 isoforms in human kidney cells and in frog oocytes grown in vitro, and measured their temperature sensitivity using calcium imaging and electrophysiological assays, respectively. As expected, cells producing the long isoform were activated at 40 degrees Celsius (104° F). Cells producing the short isoform, on the other hand, were activated at just 30 degrees (86° F)—a drop that allows the protein to respond to the warmth of the vampire bats’ prey.

“This is a big jump in understanding how these animals locate their prey,” said Brock Fenton, a biology professor at the University of Western Ontario and author of an accompanying Nature News and Views article. While the longer isoform maintains its normal function of detecting potentially harmful high temperatures, the shorter isoform in the trigeminal nerves of the common vampire bat allows the animals to detect lower temperatures, such as the body heat of their mammalian prey.

“Basically, evolution tweaked a system in vampires bats that was already being used to sense temperatures,” said Schutt, author of the 2008 book Dark Banquet: Blood and the Curious Lives of Blood-Feeding Creatures, turning it into a useful hunting tool.

This is in contrast to the pit viper, whose infrared-sensing ability evolved from a different type of channel not involved in heat detection, but in the detection of noxious smells, added Fenton. The different evolutionary strategies employed by these two lineages “is an example of how plastic our sensory systems can be,” he said.

Posted in: bat,dorsal root ganglia,heat sensing,Infrared,ion channel,membrane proteins,nerves,Neuroscience,physiology,pit viper,snake,trigeminal ganglia,TRPA,TRPV,TRPV1,vampire,Vampire bat

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New Depiction of Light Aids Telecommunications

Physicists with the Institute of Ultrafast Spectroscopy and Lasers (IUSL) at The City College of New York have presented a new way to map spiraling light that could help harness untapped data channels in optical fibers. Increased bandwidth would ease the burden on fiber-optic telecommunications networks taxed by an ever-growing demand for audio, video and digital media. The new model, developed by graduate student Giovanni Milione, Professor Robert Alfano and colleagues, could even spur enhancements in quantum computing and other applications.

Higher Order Poincare Sphere model developed by physicists with the
Institute of Ultrafast Spectroscopy and Lasers tracks movement of
complex forms of light. (Credit: Image courtesy of City College of New
York)
"People now can detect (light in) the ground channel, but this gives us a way to detect and measure a higher number of channels," says Mr. Milione. With such heavy traffic funneled through a single channel, there is great interest in exploiting others that can be occupied by complex forms of light, he explains.

The team published their work in the July 25 issue of Physical Review Letters. Mr. Milione will present it at the Optical Society of America's "Frontiers in Optics 2011" conference, October 16-20 in San Jose, Calif.

Polarization is everything to a physicist tracking light in an optical fiber or laser. More than a way to cut glare with sunglasses, polarization refers to a specific direction and orientation of the light's movement and electric field -- when it isn't going every which way as it does when emanating from a light bulb, for example.

"Being able to follow polarization and other changes as light travels gives you insight into the material it travels through, " explains Milione. This helps control the light and can essentially give a fingerprint of the material being analyzed.

Detecting the polarization also lets users finely tune a laser. Such control can allow a laser to burn away one layer of material while leaving the other layers it passes through intact.

Until now, only the simplest form of light, the ground state, could be mapped and controlled. Multiple higher channels in an optical fiber, which could be occupied by more complex light, were left sitting idle.

A globe-shaped model, called the Poincaré Sphere, has long been used to map such simple light. This light has peaks and troughs, like waves on the ocean, and moves or vibrates in "plane waves." One maps how light intersects the sphere in the same way one pinpoints a location on Earth using longitude and latitude.

But complex light moves with both spin and orbital angular momentum, more or less like the movement of our moon as it spins on its axis and orbits Earth.

Such light twists like a tornado as it travels through space and takes the form of what are called vector beams and vortices. To map these vortices the researchers expanded the existing sphere to develop their Higher Order Poincaré Sphere (HOPS).

The team studies even more complex patterns of light, such as star-shaped forms. Their model uses the HOPS to reduce what could be pages of mathematics to single equations. These are the mathematical tools that will harness the complex light for use in technology.

"The sphere facilitates understanding, showing phase vortices are on poles and vector beams are on the equator," explains Milione. "It organizes the relationship between these vortices of light."

"This kind of organization on the higher level Poincaré Sphere could clear the path to a number of novel physics and engineering efforts such as quantum computing and optical transitions; could greatly expand the sensitivity of spectroscopy and the complexity of computer cryptography; and might further push the boundaries what can be 'seen'," said Dr. Alfano.

The research was funded in part by Corning Inc. and the Army Research Office. 

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Murderer Gets Reduced Sentence Because His Genes Made Him Do It

Hey criminals! Here’s how you get out of taking full responsibility for your dastardly actions:

Fake your DNA sampleBlame it on your identical twin See if you have the genes that predispose you to whatever crime you’ve committed

Murderer Abdelmalek Bayout and his attorneys chose option three. Bayout admitted in 2007 to stabbing and killing Walter Felipe Novoa Perez in Italy. During the first sentencing, he was found to be mentally ill. This year, neuroscientists also found abnormalities in brain-imaging scans and five genes linked to violent behavior, including MAOA.

Although there have been numerous cases since 1994 in which the defense argued for leniency based on MAOA deficiency, this is the first case in which this tactic has been successful. Based on the scans and genetic testing results, the judge reduced Bayout’s sentence by another year.

Not everyone agrees with the judge’s decision.

"We don’t know how the whole genome functions and the [possible] protective effects of other genes," says Giuseppe Novelli, a forensic scientist and geneticist at the University Tor Vergata in Rome. Tests for single genes such as MAOA are "useless and expensive", he adds.

Even worse, this verdict could open the floodgates to claims of all sorts the more we know about genetic influences on behavior. That list above is just about to get longer.

Source: Scientific American

Image: “Structural (left) and functional (right) MRI scan data shows that subjects with the violence-related version of the MAO-A gene (MAOA-L) had reduced volume and activity of the anterior cingulate cortex (blue area in front part of brain at left and corresponding yellow area in at right), which is thought to be the hub of a circuit responsible for regulating impulsive aggression. The color-coded areas show where subjects with the L gene type differed from subjects with the H gene type.”

NIMH Clinical Brain Disorders Branch

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DNA Network Tweet Cloud

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American Genes Don’t Exist

Congratulations to Meb Keflezighi of Eritrean descent, who won the New York City Marathon last Sunday and was the first American to do so since 1982!

Why did I mention that he was born in Eritrea? Because critics say that an immigrant like Keflezighi who moved to the U.S. at age 12 isn’t a legitimate American.

A post on Letsrun.com said:

Give us all a break. It’s just another African marathon winner.

How about making that African-American?

Silly me. I thought that naturalized American citizens equal American citizens at birth with the same rights and privileges (with the exception of getting to be the President of the United States). Leaving that debate aside, however, the belief that East Africans are genetically endowed for marathon running has also clouded Keflezighi’s celebration.

The success of distance runners from Kenya and Ethiopia has fostered a lore of East Africans as genetically gifted, unbeatable, dominant because of their biology. Scientists have looked for — but not found — genes specific to East Africans that could account for their distance ability, said John Hoberman, a professor at the University of Texas at Austin who studies race and sports.

Truly American? Debate Dogs a Triumph in the Marathon – NYTimes.com

No doubt Keflezighi has genes which enhance his physiological capabilities for endurance and other traits found in winning marathoners. This does not mean that Keflezighi is any more or less American than other non-East African runners who have the same genes.

The Oxford English Dictionary defines “nationality” in two parts:

nationality

noun (pl. nationalities) 1 the status of belonging to a particular nation. 2 an ethnic group forming a part of one or more political nations.

Even though ethnic groups are mentioned, the U.S. is clearly a country of many ethnic groups so genes should not be part of the debate when discussing whether someone is American or not.

Quite frankly, I’m not even sure what makes a person American and I don’t think anyone else does either. I hold an American passport and spent the years between ages 6 and 26 in the U.S. I’ve lived in six different countries in the past 10 years and as a result, my national identity is slightly muddled. My son is even more confused. He holds an American passport as well but has never lived in the U.S although he’s lived in four different countries in his seven years. He was born in Japan so some days he says that he’s Japanese and now that he lives in Singapore, he sometimes says he’s Singaporean. I’m sure some people would say he’s not American at all.

It might be simpler to say we’re global citizens with ties to more than one country. Truth be told, I’m proud to say I’m Chinese-American with the accent to prove it.

Edited to add this video of Meb Keflezighi on David Letterman:

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Genetic Genealogy on Faces of America

Quite a line-up of celebrities!

Eva Longoria, Meryl Streep, Mario Batali, Stephen Colbert, Malcolm Gladwell, Yo-Yo Ma, Mike Nichols, Kristi Yamaguchi, Elizabeth Alexander, Queen Noor and Louise Erdrich have all submitted DNA tests for a new PBS television series FACES OF AMERICA.

 

Faces of America with Henry Louis Gates, Jr. airs on Wednesdays, February 10 – March 3, 2010 from 8-9 p.m. ET on PBS.

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Video: Knome’s Ari Kiirikki Speaks with Medgadget

via Medgadget

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Knowledge about Genetic Risk is Power or is it Fear?

A little over two years ago, I confessed that I was “just a little scared of genetic testing.” I have two young children and almost every day I see traits in them that I’m pretty sure they inherited from me whether via genes or behavior. If you’re a parent, I’m sure you can imagine that there’s a lot of self-blame going on in our house.

So when it comes to genetic testing, I should want to know but I don’t. At least not right this minute. Haven’t I got enough to worry about?

From Middletown Journal’s month-long series on the battle against cancer – Many with cancer gene don’t want to know.

There are people out there who may not want to know. There’s a subset of people who if they knew would act on the information and benefit and there are others who would rather bury their heads in the sand.

~Dr. Michael Watson, director of the American College of Medical Genetics

NIH Director Francis Collins, however, falls squarely in the camp of those who not only want to know, they act on the info. Well done!

Collins hits the gym following genetic testing from The Great Beyond, Nature blog

Maybe if a genetic test could motivate me to go to the gym and lose weight, it would be worth it.

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DNA{wesome}

That’s right, baby!

via Buzzfeed

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Genetics = Real Science

Matchmaking services are adding DNA testing to their list of offers. The DNA test analyzes HLA genes of the immune system that influence a person’s body odor. The theory is that people are attracted to those whose HLA genes and body odor differ from their own so that their potential offspring have the possibility of inheriting a more varied set of HLA genes leading to enhanced health due to a stronger immune system.

In an Associated Press article, Dr. Rocio Moran, medical director of the General Genetics Clinic at the Cleveland Clinic said:

They are just trying to make a buck. That if it’s genetic, it must be real science.

That’s the kind of argument some shady companies are making about direct-to-consumer genetic testing. It reminds me of the ruckus earlier this year over companies that offer genetic testing to parents who’re interested in having their children tested for athletic prowess and other abilities.

If it’s genetic, it must be real science.

If it’s science, it must be true.

Anyone living in the real world knows that genetics and science can only carry you so far. In the end, what it comes down to is the kind of person you are in spite of your genes. That doesn’t mean a genetic test is worthless. If you’re the kind of person that thinks a DNA test holds some kind of magic then maybe you will be able to find a mate who thinks the same way. After all, there’s a lid for every pot.

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Lopez Tonight First Late-Night Show to Offer DNA Testing

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Larry David’s DNA Test

I’d like to know which loci they used to decide he is 37% native American!

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