What Happens When You Pop A Quantum Balloon?

Source:

http://www.sciencedaily.com/releases/2008/04/080417155913.htm

ScienceDaily (Apr. 20, 2008) — When a tiny, quantum-scale, hypothetical balloon is popped in a vacuum, do the particles inside spread out all over the place as predicted by classical mechanics".
The question is deceptively complex, since quantum particles do not look or act like air molecules in a real balloon. Matter at the infinitesimally small quantum scale is both a wave and a particle, and its location cannot be fixed precisely because measurement alters the system.
Now, theoretical physicists at the University of Southern California and the University of Massachusetts Boston have proven a long-standing hypothesis that quantum-scale chaos exists ... sort of.
Writing in the April 17 edition of Nature, senior author Maxim Olshanii reported that when an observer attempts to measure the energies of particles coming out of a quantum balloon, the interference caused by the attempt throws the system into a final, "relaxed" state analogous to the chaotic scattering of air molecules.
The result is the same for any starting arrangement of particles, Olshanii added, since the act of measuring wipes out the differences between varying initial states.
"It's enough to know the properties of a single stationary state of definite energy of the system to predict the properties of the thermal equilibrium (the end state)," Olshanii said.
The measurement -- which must involve interaction between observer and observed, such as light traveling between the two -- disrupts the "coherent" state of the system, Olshanii said.
In mathematical terms, the resulting interference reveals the final state, which had been hidden in the equations describing the initial state of the system.
"The thermal equilibrium is already encoded in an initial state," Olshanii said. "You can see some signatures for the future equilibrium. They were already there but more masked by quantum coherences."
The finding holds implications for the emerging fields of quantum computing and quantum information theory, said Paolo Zanardi, an associate professor of physics studying quantum information at USC.
In Zanardi's world, researchers want to prevent coherent systems from falling into the chaos of thermal equilibrium.
"Finding such 'unthermalizable' states of matter and manipulating them is exactly one of those things that quantum information/computation folks like me would love to do," Zanardi wrote. "Such states would be immune from 'decoherence' (loss of quantum coherence induced by the coupling with environment) that's still the most serious, both conceptually and practically, obstacle between us and viable quantum information processing."
Zanardi and a collaborator introduced the notion of "decoherence-free" quantum states in 1997. Researchers such as Zanardi and Daniel Lidar, associate professor of chemistry, among others, have helped make USC a major center for the study of quantum computing.
Olshanii and his co-authors, postdoctoral researchers Marcos Rigol and Vanja Dunjko, developed their theory of quantum thermal equilibrium at USC and completed their work at the University of Massachusetts Boston.
Their research was funded by the National Science Foundation and the Office of Naval Resarch.
Adapted from materials provided by University of Southern California, via EurekAlert!, a service of AAAS.

Fausto Intilla - www.oloscience.com

Prototype Terahertz Imager Promises Advances In Biochemistry

Source:

http://www.sciencedaily.com/releases/2008/04/080415164314.htm

ScienceDaily (Apr. 15, 2008) — Researchers at the National Institute of Standards and Technology (NIST) have demonstrated a new imaging system that detects naturally occurring terahertz radiation with unprecedented sensitivity and resolution. The technology may become a new tool chemical and biochemical analyses ranging from early tumor detection to rapid and precise identification of chemical hazards for homeland security instruments.
Terahertz radiation falls between microwaves and infrared radiation on the electromagnetic spectrum, with frequencies from about 300 million cycles per second to about 3 trillion cycles per second. Biological and chemical samples naturally emit characteristic signatures of terahertz radiation, but detecting and measuring them is a unique challenge because the signals are weak and absorbed rapidly by the atmosphere.
The NIST prototype imager, described in detail for the first time in a new paper,* uses an exquisitely sensitive superconducting detector combined with microelectronics and optics technologies to operate in the terahertz range. The NIST system has its best resolution centered around a frequency of 850 gigahertz, a "transmission window" where terahertz signals can pass through the atmosphere. The system can detect temperature differences smaller than half a degree Celsius, which helps to differentiate between, for example, tumors and healthy tissue.
The heart of the system is a tiny device that measures incoming terahertz radiation by mixing it with a stable internal terahertz signal. This mixing occurs in a thin-film superconductor, which changes temperature upon the arrival of even a minute amount of radiation energy. The slight frequency difference between the two original terahertz signals produces a more easily detected microwave frequency signal.
NIST developed the device and antenna, combined with an amplifier on a chip smaller than a penny, in collaboration with the University of Massachusetts. Called a hot electon bolometer (HEB), the technology is sensitive enough to detect the weak terahertz signals naturally emitted by samples, eliminating the need to generate terahertz radiation to actively illuminate the samples. This greatly reduces complexity and minimizes safety concerns. In addition, the NIST "mixer" system delivers more information by detecting both the magnitude and phase (the point where each individual wave begins) of the radiation.
Because passively emitted signals are so weak, the current system takes about 20 minutes to make a single 40 x 40 pixel image. NIST researchers are working on an improved version that will scan faster and operate at two frequencies at once. Future systems also should be able to achieve better spatial resolution.
* E. Gerecht, D. Gu, L. You and S. Yngvesson. Passive heterodyne hot electron bolometer imager operating at 850 GHz. Forthcoming in IEEE Transactions on Microwave Theory and Techniques.
Adapted from materials provided by National Institute of Standards and Technology.

Fausto Intilla - www.oloscience.com

Innovative Composite Opens Terahertz Frequencies To Many Applications

Source:

http://www.sciencedaily.com/releases/2008/04/080415185016.htm

ScienceDaily (Apr. 16, 2008) — A frequency-agile metamaterial that for the first time can be tuned over a range of frequencies in the so-called "terahertz gap" has been engineered by a team of researchers from Boston College, Los Alamos National Laboratory and Boston University.

The team incorporated semiconducting materials in critical regions of tiny elements -- in this case metallic split-ring resonators -- that interact with light in order to tune metamaterials beyond their fixed point on the electromagnetic spectrum, an advance that opens these novel devices to a broader array of uses, according to findings published in the online version of the journal Nature Photonics.
"Metamaterials no longer need to be constructed only out of metallic components," said Boston College Physicist Willie J. Padilla, the project leader. "What we've shown is that one can take the exotic properties of metamaterials and combine them with the unique prosperities of natural materials to form a hybrid that yields superior performance."
Padilla and BC graduate student David Shrekenhamer, along with Hou-Tong Chen, John F. O'Hara, Abul K Azad and Antoinette J. Tayler of Los Alamos National Laboratory, and Boston University's Richard D. Averitt formed a single layer of metamaterial and semiconductor that allowed the team to tune terahertz resonance across a range of frequencies in the far-infrared spectrum.
The team's first-generation device achieved 20 percent tuning of the terahertz resonance to lower frequencies -- those in the far-infrared region --addressing the critical issue of narrow band response typical of all metamaterial designs to date.
Constructed on the micron-scale, metamaterials are composites that use unique metallic contours in order to produce responses to light waves, giving each metamaterial its own unique properties beyond the elements of the actual materials in use.
Within the past decade, researchers have sought ways to significantly expand the range of material responses to waves of electromagnetic radiation -- classified by increasing frequency as radio waves, microwaves, terahertz radiation, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays. Numerous novel effects have been demonstrated that defy accepted principles.
"Metamaterials demonstrated negative refractive index and up until that point the commonly held belief was that only a positive index was possible," said Padilla. "Metamaterials gave us access to new regimes of electromagnetic response that you could not get from normal materials."
Prior research has shown that because they rely on light-driven resonance, metamaterials experience frequency dispersion and narrow bandwidth operation where the centre frequency is fixed based on the geometry and dimensions of the elements comprising the metamaterial composite. The team believes that the creation of a material that addresses the narrow bandwidth limitations can advance the use of metamaterials.
Enormous efforts have focused on the search for materials that could respond to terahertz radiation, a scientific quest to find the building blocks for devices that could take advantage of the frequency for imaging and other applications.
Potential applications could lie in medical imaging or security screening, said Padilla. Materials undetectable through x-ray scans -- such as chemicals, biological agents, and certain explosives -- can provide a unique "fingerprint" when struck by radiation in the far-infrared spectrum. Metamaterials like the one developed by the research team will facilitate future devices operating at the terahertz frequency of the electromagnetic spectrum.
In addition to imaging and screening, researchers and high-tech companies are probing the use of terahertz in switches, modulators, lenses, detectors, high bit-rate communications, secure communications, the detection of chemical and biological agents and characterization of explosives, according to Los Alamos National Laboratory.
Adapted from materials provided by Boston College, via EurekAlert!, a service of AAAS.

Fausto Intilla - www.oloscience.com

Artificial Lightning: Laser Triggers Electrical Activity In Thunderstorm For The First Time

Source: http://www.sciencedaily.com/releases/2008/04/080414082517.htm

ScienceDaily (Apr. 14, 2008) — A team of European scientists has deliberately triggered electrical activity in thunderclouds for the first time, according to a new paper in the latest issue of Optics Express, the Optical Society's (OSA) open-access journal. They did this by aiming high-power pulses of laser light into a thunderstorm.

At the top of South Baldy Peak in New Mexico during two passing thunderstorms, the researchers used laser pulses to create plasma filaments that could conduct electricity akin to Benjamin Franklin's silk kite string. No air-to-ground lightning was triggered because the filaments were too short-lived, but the laser pulses generated discharges in the thunderclouds themselves.
"This was an important first step toward triggering lightning strikes with laser beams," says Jérôme Kasparian of the University of Lyon in France. "It was the first time we generated lighting precursors in a thundercloud." The next step of generating full-blown lightning strikes may come, he adds, after the team reprograms their lasers to use more sophisticated pulse sequences that will make longer-lived filaments to further conduct the lightning during storms.
Triggering lightning strikes is an important tool for basic and applied research because it enables researchers to study the mechanisms underlying lightning strikes. Moreover, triggered lightning strikes will allow engineers to evaluate and test the lightning-sensitivity of airplanes and critical infrastructure such as power lines.
Pulsed lasers represent a potentially very powerful technology for triggering lightning because they can form a large number of plasma filaments -- ionized channels of molecules in the air that act like conducting wires extending into the thundercloud. This is such a simple concept that the idea of using lasers to trigger lightning strikes was first suggested more than 30 years ago. But scientists have not been able to accomplish this to date because previous lasers have not been powerful enough to generate long plasma channels. The current generation of more powerful lasers, like the one developed by Kasparian's team, may change that.
Kasparian and his colleagues involved in the Teramobile project, an international program initiated by National Center for Scientific Research (CNRS) in France and the German Research Foundation (DFG), built a powerful mobile laser capable of generating long plasma channels by firing ultrashort laser pulses. They chose to test their laser at the Langmuir Laboratory in New Mexico, which is equipped to measure atmospheric electrical discharges. Sitting at the top of 10,500-foot South Baldy Peak, this laboratory is in an ideal location because its altitude places it close to the high thunderclouds.
During the tests, the research team quantified the electrical activity in the clouds after discharging laser pulses. Statistical analysis showed that their laser pulses indeed enhanced the electrical activity in the thundercloud where it was aimed--in effect they generated small local discharges located at the position of the plasma channels.
The limitation of the experiment, though, was that they could not generate plasma channels that lived long enough to conduct lightning all the way to the ground. The plasma channels dissipated before the lightning could travel more than a few meters along them. The team is currently looking to increase the power of the laser pulses by a factor of 10 and use bursts of pulses to generate the plasmas much more efficiently.
Lightning strikes have been the subject of scientific investigation dating back to the time of Benjamin Franklin, but despite this, remain not fully understood. Although scientists have been able to trigger lightning strikes since the 1970s by shooting small rockets into thunderclouds that spool long wires connected to the ground, typically only 50 percent of rocket launches actually trigger a lightning strike. The use of laser technology would make the process quicker, more efficient and cost-effective and would be expected to open a number of new applications.
Kasparian conducted the research with his colleagues at CNRS, the University of Lyon, the University of Geneva, École Polytechnique and ENSTA in Palaiseau, France, the Free University of Berlin and the Dresden-Rossendorf Research Center as part of the Teramobile project. This work was funded jointly by the CNRS, DFG, the French and German ministries of foreign affairs, Agence Nationale de la Recherche, Fonds national suisse de la recherche scientifique, and the Swiss Secrétariat d'État à l'Éducation et à la Recherche.
Paper: "Electric events synchronized with laser filaments in thunderclouds," Jérôme Kasparian et al, Optics Express, Vol. 16, Issue 8, April 14, 2008, pp. 5757-63; abstract at http://www.opticsexpress.org/abstract.cfm?id=157189.
Adapted from materials provided by Optical Society of America, via EurekAlert!, a service of AAAS.

Fausto Intilla - www.oloscience.com

Newly Discovered Fundamental State Of Matter, A Superinsulator, Has Been Created

Source:

http://www.sciencedaily.com/releases/2008/04/080408160614.htm

ScienceDaily (Apr. 9, 2008) — Superinsulation may sound like a marketing gimmick for a drafty attic or winter coat. But it is actually a newly discovered fundamental state of matter created by scientists at the U.S. Department of Energy's Argonne National Laboratory in collaboration with several European institutions. This discovery opens new directions of inquiry in condensed matter physics and breaks ground for a new generation of microelectronics.

Led by Argonne senior scientist Valerii Vinokur and Russian scientist Tatyana Baturina, an international team of scientists from Argonne, Germany, Russia and Belgium fashioned a thin film of titanium nitride which they then chilled to near absolute zero. When they tried to pass a current through the material, the researchers noticed that its resistance suddenly increased by a factor of 100,000 once the temperature dropped below a certain threshold. The same sudden change also occurred when the researchers decreased the external magnetic field.
Like superconductors, which have applications in many different areas of physics, from accelerators to magnetic-levitation (maglev) trains to MRI machines, superinsulators could eventually find their way into a number of products, including circuits, sensors and battery shields.
If, for example, a battery is left exposed to the air, the charge will eventually drain from it in a matter of days or weeks because the air is not a perfect insulator, according to Vinokur. "If you pass a current through a superconductor, then it will carry the current forever; conversely, if you have a superinsulator, then it will hold a charge forever," he said.
"Titanium nitride films, as well as films prepared from some other materials, can be either superconductors or insulators depending on the thickness of the film," Vinokur said. "If you take the film which is just on the insulating side of the transition and decrease the temperature or magnetic field, then the film all of a sudden becomes a superinsulator."
Scientists could eventually form superinsulators that would encapsulate superconducting wires, creating an optimally efficient electrical pathway with almost no energy lost as heat. A miniature version of these superinsulated superconducting wires could find their way into more efficient electrical circuits.
Titanium nitride's sudden transition to a superinsulator occurs because the electrons in the material join together in twosomes called Cooper pairs. When these Cooper pairs of electrons join together in long chains, they enable the unrestricted motion of electrons and the easy flow of current, creating a superconductor. In superinsulators, however, the Cooper pairs stay separate from each other, forming self-locking roadblocks.
"In superinsulators, Cooper pairs avoid each other, creating enormous electric forces that oppose penetration of the current into the material," Vinokur said. "It's exactly the opposite of the superconductor," he added.
The theory behind the experiment stemmed from Argonne's Materials Theory Institute, which Vinokur organized six years ago in the laboratory's Materials Science Division. The MTI hosts a handful of visiting scholars from around the world to perform cutting-edge research on the most pressing questions in condensed matter physics. Upon completion of their tenure at Argonne, these scientists return to their home institutions but continue to collaborate on the joint projects. The MTI attracts the world's best condensed matter scientists, including Russian "experimental star" Tatyana Baturina, who, according to Vinokur, "became a driving force in our work on superinsulators."
Scientists from the Institute of Semiconductor Physics in Novosibirsk, Russia, Regensburg and Bochum universities in Germany and Interuniversity Microelectronics Centre in Leuven, Belgium, also participated in the research.
The research appears in the April 3 issue of Nature.
Adapted from materials provided by DOE/Argonne National Laboratory.

Fausto Intilla
www.oloscience.com

Desktop Device Generates And Traps Rare Ultracold Molecules

Source:

http://www.sciencedaily.com/releases/2007/12/071212201158.htm

ScienceDaily (Dec. 17, 2007) — Physicists at the University of Rochester have combined an atom-chiller with a molecule trap, creating for the first time a device that can generate and trap huge numbers of elusive-yet-valuable ultracold polar molecules.

Scientists believe ultracold polar molecules will allow them to create exotic artificial crystals and stable quantum computers.
"The neat thing about this technology is that it's a very simple, but highly efficient method," says Jan Kleinert, a doctoral physics student at the University of Rochester and designer of the new device. "It lets us produce huge quantities of these ultracold polar molecules, which opens so many doors for us."
The Thin WIre electroStatic Trap, or TWIST, is the first electrostatic polar molecule trap that works simultaneously with a magneto-optical atom trap. This means Kleinert can use the lasers of the magneto-optical trap, or MOT, to chill atoms to just a few millionths of a degree above absolute zero, then force the atoms to group into molecules, and instantaneously hold them in place with the electrostatic TWIST trap.
Traditionally, a complex process of creating and trapping is required to produce these molecules, akin to repeatedly emptying and refilling the ice cube trays in your freezer, says Kleinert. A MOT with a TWIST, however, can create and store the chilled molecules in one place, instantly—more like a refrigerator with an automatic icemaker.
While polar molecules are literally as common as water, and dozens of laboratories around the world can cool atoms to such extreme temperatures, creating an ultracold polar molecule is difficult. Ultracold atoms can combine into molecules, but since only one type of atom can usually be cooled at once, the molecules it makes are electrically symmetric, not polar. Physicists have to either chill regular polar molecules, or chill several types of atoms at the same time and force them to join into molecules. Both processes are so complex that Kleinert says only four laboratories in the world do them, and the yield of ultracold polar molecules until now has been very low.
The TWIST, developed with Kleinert's advisor, Nicholas P. Bigelow, Lee A. DuBridge Professor of Physics at the University of Rochester, makes the complex process much more efficient, and thus makes available many more of these molecules.
The secret to the TWIST is the precise thickness of the tungsten wires that loop around the molecule-production area. In Kleinert's design, atoms are chilled with the lasers of a MOT, which drains away the atoms' energy, chilling them to nearly 460 degrees Fahrenheit below zero.
So far, this is exactly the same as the traditional method, but Kleinert surrounds his target area with tungsten loops that create an electric field. The field has no effect on the chilled atoms, but as the atoms are grouped into polar molecules by a process called photoassociation, the new polar molecules, with a positive charge on one side and a negative charge on the other, are affected by the field.
The electric field has a gradient, and due to some of the strange properties of the quantum world, polar molecules tend to "slide down" that gradient, collecting in the center of the field. As a result, says Kleinert, the TWIST collects and holds the low-field seeking polar molecules but lets other unaffected particles, such as atoms or other molecules, simply drift away.
Those tungsten loops have to be thick enough that they can withstand the electrostatic forces they generate, but thin enough that they don't block the MOT laser initiating the cooling. After months of trial and error and a lot of burned-out tungsten wire, Kleinert found that wires just the width of a hair provided the perfect balance.
"The coldest molecules so far have been produced from MOTs, but until the TWIST came along, electric field trapping and MOTs just didn't go together," says Kleinert. "Now we can accumulate these polar molecules continuously, without switching from creation to storage and back again."
With a good supply of ultracold polar molecules, computer scientists would have a new tool with which to tackle the creation of quantum computers, says Kleinert.
Quantum computer scientists are attracted to ultracold particles because their temperatures reduce decoherence, a phenomenon where your system decays from the carefully prepared quantum configuration you started with, to a classical physics state, which loses all the advantages quantum computers hold.
Ultracold polar molecules in particular are especially attractive because their strong polarity allows them to interact with each other over much larger distances than other atomic particles, and the stronger the interaction between particles, the faster a quantum computer can perform certain operations.
Ultracold polar molecules may even allow scientists to venture into an unknown quarter of the Standard Model of Physics—the size of the electron, says Kleinert. The answer to whether the electron has a definite size or is just a dimensionless point in space could support the Standard Model, or support one of the many alternate models. Trying to approximate the electron's size would likely require ultracold polar molecules, which can have 100 times the sensitivity of simple ultracold atoms. That difference could be enough to make a definitive measurement supporting or chipping away at the Standard Model altogether.
Adapted from materials provided by University of Rochester.

Fausto Intilla

www.oloscience.com

Ultrafast Optical Shutter Is Switched Entirely By Laser Light

Source:

http://www.sciencedaily.com/releases/2007/12/071206155526.htm

ScienceDaily (Dec. 7, 2007) — It's a rare case of all light and no heat: A new study reports that a laser can be used to switch a film of vanadium dioxide back and forth between reflective and transparent states without heating or cooling it.

It is one of the first cases that scientists have found where light can directly produce such a physical transition without changing the material's temperature.
It is also among the most recent examples of "coherent control," the use of coherent radiation like laser light to affect the behavior of atomic, molecular or electronic systems. The technique has been used to control photosynthesis and is being used in efforts to create quantum computers and other novel electronic and optical devices. The new discovery opens the possibility of a new generation of ultra-fast optical switches for communications.
The study, which was published in the Sept. 14 issue of Physical Review Letters, was conducted by a team of physicists from Vanderbilt University and the University of Konstanz in Germany headed by Richard Haglund of Vanderbilt and Alfred Leitenstorfer from Konstanz.
Vanadium dioxide's uncanny ability to switch back and forth between transparent and reflective states is well known. At temperatures below 154 degrees Fahrenheit, vanadium dioxide film is a transparent semiconductor. Heat it to just a few degrees higher, however, and it becomes a reflective metal. The semiconducting and metallic states actually have different crystalline structures. Among a number of possible applications, people have experimented with using vanadium dioxide film as the active ingredient in "thermochromic windows" that can block sunlight when the temperature soars and as microscopic thermometers that could be injected into the body.
In 2005, a research collaboration teaming Haglund and René Lopez (now at the University of North Carolina, Chapel Hill) with Andrea Cavalleri and Matteo Rini from the Lawrence Berkeley National Laboratory tested the vanadium dioxide transition with an ultra-fast laser that produced 120-femtosecond pulses. (A femtosecond is a quadrillionth of a second. At this time scale, an eye blink lasts almost forever. In the three-tenths of a second it takes to blink an eye, light can travel 56,000 miles. By contrast, it takes 100 femtoseconds to cross the width of a human hair.)
Using this laser, the researchers determined that VO2 film can flip from transparent to reflective in a remarkably short time: less than 100 femtoseconds. This was the fastest phase transition ever measured. However, the mechanism that allowed it to make such rapid transitions remained a matter of scientific debate.
Now, in a two-year collaboration with the Leitenstorfer group, the Vanderbilt researchers have used a laser with even shorter, 12-femtosecond pulses to "strobe" the vanadium dioxide transition with the fastest pulses ever used for this purpose. The result? "This transition takes place even faster than we thought possible," says Haglund. "It can shift from transparent to reflective and back to transparent again in less than 100 femtoseconds, making the transition more than twice as fast as we had thought."
In order to identify the driving mechanism for the rapid change of state in vanadium dioxide, Leitenstorfer's graduate student Carl Kübler developed a method that converts the near-infrared photons produced by their 12-femtosecond pulse laser into a broad spectrum of infrared wavelengths that bracket a well-known vibration in the vanadium dioxide crystal lattice. At the same time, the Vanderbilt researchers figured out how to grow VO2 film on a diamond substrate that is transparent to infrared light.
This allowed the researchers to show that the energy in the laser beam goes directly into the crystal lattice of the VO2, driving it to shift from its transparent, crystalline form to its more compact and symmetric metallic configuration.
The laser light doesn't produce this shift by heating the VO2 lattice until it melts, as the conventional wisdom about phase transitions suggested. Instead, the researchers found that the stream of photons directly drive the oxygen atoms from one position to another by a process that is rather like pumping a swing in time with its natural frequency.
"People have believed for a long time that what happened in this phase transition was that the electrons get excited and then, somehow or another, the crystal structure changes," says Haglund. "But it turns out that the change in crystal structure is associated with this coherent molecular vibration."
Such a rapid transition is only possible because the difference between the metallic and semiconductor geometries is extremely small. "You can think of the movement that results as a breathing motion of the oxygen 'cage' that surrounds the vanadium ions," says Haglund. "That makes it possible for the structure to change from the semiconducting to the metallic states. It's a little like taking a deep breath to get into last summer's clothes."
This mechanism also allows the researchers to trigger the transition without changing the film's temperature. "We can focus the laser beam on a transparent vanadium dioxide film and create a small reflective spot. We can switch it on and off in less than 100 femtoseconds provided we haven't dumped so much energy into the film that we've heated it up. However, the more laser energy you dump in the VO2, the longer it takes to return to the semiconducting state," Haglund says.
Henri Ehrke and Rupert Huber from the University of Konstanz, and Andrej Halabica from Vanderbilt University also collaborated in the study, which was funded by the National Science Foundation and the Alexander von Humboldt Foundation.
Adapted from materials provided by Vanderbilt University.

Fausto Intilla

www.oloscience.com