sabato 25 luglio 2009

Nanotubes Weigh A Single Atom


SOURCE

ScienceDaily (July 23, 2009) — How can you weigh a single atom? European researchers have built an exquisite new device that can do just that. It may ultimately allow scientists to study the progress of chemical reactions, molecule by molecule.
Carbon nanotubes are ultra-thin fibres of carbon and a nanotechnologist’s dream.
They are made from thin sheets of carbon only one atom thick – known as graphene – rolled into a tube only a few nanometres across. Even the thickest is more than a thousand times thinner than a human hair.
Interest in carbon nanotubes blossomed in the 1990s when they were found to possess impressive characteristics that make them very attractive raw materials for nanotechnology of all kinds.
“They have unique properties,” explains Professor Pertti Hakonen of Helsinki University of Technology. “They are about 1000 times stronger than steel and very good thermal conductors and good electrical conductors.”
Hakonen is coordinator of the EU-funded CARDEQ project (
http://www.cardeq.eu/) which is exploiting these intriguing materials to build a device sensitive enough to measure the masses of atoms and molecules.
Vibrating strings
A carbon nanotube is essentially an extremely thin, but stiff, piece of string and, like other strings, it can vibrate. As all guitar players know, heavy strings vibrate more slowly than lighter strings, so if a suspended carbon nanotube is allowed to vibrate at its natural frequency, that frequency will fall if atoms or molecules become attached to it.
It sounds simple and the idea is not new. What is new is the delicate sensing system needed to detect the vibration and measure its frequency. Some nanotubes turn out to be semiconductors, depending on how the graphene sheet is wound, and it is these that offer the solution that CARDEQ has developed.
Members of the consortium have taken the approach of building a semiconducting nanotube into a transistor so that the vibration modulates the current passing through it. “The suspended nanotube is, at the same time, the vibrating element and the readout element of the transistor,” Hakonen explains.
“The idea was to run three different detector plans in parallel and then select the best one,” he says. “Now we are down to two. So we have the single electron transfer concept, which is more sensitive, and the field effect transistor concept, which is faster.”
Single atoms
Last November, CARDEQ partners in Barcelona reported that they had sensed the mass of single chromium atoms deposited on a nanotube. But Hakonen says that even smaller atoms, of argon, can now be detected, though the device is not yet stable enough for such sensitivity to be routine. “When the device is operating well, we can see a single argon atom on short time scales. But then if you measure too long the noise becomes large.”
CARDEQ is not alone in employing carbon nanotubes as mass sensors. Similar work is going on at two centres in California – Berkeley and Caltech – though each has adopted a different method to measuring the mass.
All three groups have announced they can perform mass detection on the atomic level using nanotubes, but CARDEQ researchers provided the most convincing data with a clear shift in the resonance frequency.
But a single atom is nowhere near the limit of what is possible. Hakonen is confident they can push the technology to detect the mass of a single nucleon – a proton or neutron.
“It’s a big difference,” he admits, “but typically the improvements in these devices are jump-like. It’s not like developing some well-known device where we have only small improvements from time to time. This is really front-line work and breakthroughs do occur occasionally.”
Biological molecules
If the resolution can be pared down to a single nucleon, then researchers can look forward to accurately weighing different types of molecules and atoms in real time.
It may then become possible to observe the radioactive decay of a single nucleus and to study other types of quantum mechanical phenomena.
But the real excitement would be in tracking chemical and biological reactions involving individual atoms and molecules reacting right there on the vibrating nanotube. That could have applications in molecular biology, allowing scientists to study the basic processes of life in unprecedented detail. Such practical applications are probably ten years away, Hakonen estimates.
“It will depend very much on how the technology for processing carbon nanotubes develops. I cannot predict what will happen, but I think chemical reactions in various systems, such as proteins and so on, will be the main applications in the future.”
The CARDEQ project received funding from the FET-Open strand of the EU’s Sixth Framework Programme for ICT research.
Adapted from materials provided by
ICT Results.

Physicists Create First Nanoscale Mass Spectrometer


ScienceDaily (July 24, 2009) — Using devices millionths of a meter in size, physicists at the California Institute of Technology (Caltech) have developed a technique to determine the mass of a single molecule, in real time.
The mass of molecules is traditionally measured using mass spectrometry, in which samples consisting of tens of thousands of molecules are ionized, to produce charged versions of the molecules, or ions. Those ions are then directed into an electric field, where their motion, which is choreographed by both their mass and their charge, allows the determination of their so-called mass-to-charge ratio. From this, their mass can ultimately be ascertained.
The new technique, developed over 10 years of effort by Michael L. Roukes, a professor of physics, applied physics, and bioengineering at the Caltech and codirector of Caltech's Kavli Nanoscience Institute, and his colleagues, simplifies and miniaturizes the process through the use of very tiny nanoelectromechanical system (NEMS) resonators. The bridge-like resonators, which are 2 micrometers long and 100 nanometers wide, vibrate at a high frequency and effectively serve as the "scale" of the mass spectrometer.
"The frequency at which the resonator vibrates is directly proportional to its mass," explains research physicist Askshay Naik, the first author of a paper about the work that appears in the journal Nature Nanotechnology. Changes in the vibration frequency, then, correspond to changes in mass.
"When a protein lands on the resonator, it causes a decrease in the frequency at which the resonator vibrates and the frequency shift is proportional to the mass of the protein," Naik says.
As described in the paper, the researchers used the instrument to test a sample of the protein bovine serum albumin (BSA), which is known to have a mass of 66 kilodaltons (kDa; a dalton is a unit of mass used to describe atomic and molecular masses, with one dalton approximately equal to the mass of one hydrogen atom).
The BSA protein ions are produced in vapor form using an electrospray ionization (ESI) system.The ions are then sprayed on to the NEMS resonator, which vibrates at a frequency of 450 megahertz. "The flux of proteins reaching the NEMS is such that only one to two protein lands on the resonator in a minute," Naik says.
When the BSA protein molecule is dropped onto the resonator, the resonator's vibration frequency decreases by as much as 1.2 kiloHertz—a small, but readily detectable, change. In contrast, the beta-amylase protein molecule, which has a mass of about 200 kDa, or three times that of BSA, causes a maximum frequency shift of about 3.6 kHz.
In principle, Naik says, it should be possible to use the system to detect one dalton differences in mass, the equivalent of a single hydrogen atom, but this will require a next-generation of nanowire-based devices that are smaller and have even better noise performance.
Because the location where the protein lands on the resonator also affects the frequency shift—falling onto the center of the resonator causes a larger change than landing on the end or toward the sides, for example—"we can't tell the mass with a single measurement, but needed about 500 frequency jumps in the published work," Naik says. In future, the researchers will decouple measurements of the mass and the landing position of the molecules being sampled. This technique, which they have already prototyped, will soon enable mass spectra for complicated mixtures to be built up, molecule-by molecule.
Eventually, Roukes and colleagues hope to create arrays of perhaps hundreds of thousands of the NEMS mass spectrometers, working in parallel, which could determine the masses of hundreds of thousands of molecules "in an instant," Naik says.
As Roukes points out, "the next generation of instrumentation for the life sciences—especially those for systems biology, which allows us to reverse-engineer biological systems—must enable proteomic analysis with very high throughput. The potential power of our approach is that it is based on semiconductor microelectronics fabrication, which has allowed creation of perhaps mankind's most complex technology."
The other authors of the paper are graduate student Mehmet S. Hanay and staff scientist Philip Feng, from Caltech, and Wayne K. Hiebert of the National Research Council of Canada. The work was supported by the National Institutes of Health and, indirectly, by the Defense Advanced Research Projects Agency and the Space and Naval Warfare Systems Command.
Journal reference:
. Towards single-molecule nanomechanical mass spectrometry. Nature Nanotechnology, July 4, 2009
Adapted from materials provided by
California Institute of Technology.

giovedì 23 luglio 2009

Purer Water With Long Shelf Life Made Possible With One Atom Change To Water Purification Product


ScienceDaily (July 23, 2009) — By substituting a single atom in a molecule widely used to purify water, researchers at Sandia National Laboratories have created a far more effective decontaminant with a shelf life superior to products currently on the market.
Sandia has applied for a patent on the material, which removes bacterial, viral and other organic and inorganic contaminants from river water destined for human consumption, and from wastewater treatment plants prior to returning water to the environment.
“Human consumption of ‘challenged’ water is increasing worldwide as preferred supplies become more scarce,” said Sandia principal investigator May Nyman. “Technological advances like this may help solve problems faced by water treatment facilities in both developed and developing countries.”
The study was published in June 2009 in the journal Environmental Science & Technology (a publication of the American Chemical Society) and highlighted in the June 22 edition of Chemical & Engineering News. Sandia is working with a major producer of water treatment chemicals to explore the commercial potential of the compound.
The water-treatment reagent, known as a coagulant, is made by substituting an atom of gallium in the center of an aluminum oxide cluster — itself a commonly used coagulant in water purification, says Nyman.
The substitution isn’t performed atom by atom using nanoscopic tweezers but rather uses a simple chemical process of dissolving aluminum salts in water, gallium salts into a sodium hydroxide solution and then slowly adding the sodium hydroxide solution to the aluminum solution while heating.
“The substitution of a single gallium atom in that compound makes a big difference,” said Nyman. “It greatly improves the stability and effectiveness of the reagent. We’ve done side-by-side tests with a variety of commercially available products. For almost every case, ours performs best under a wide range of conditions.”
Wide-ranging conditions are inevitable, she said, when dealing with a natural water source such as a river. “You get seasonal and even daily fluctuations in pH, temperature, turbidity and water chemistry. And a river in central New Mexico has very different conditions than say, a river in Ohio.”
The Sandia coagulant attracts and binds contaminants so well because it maintains its electrostatic charge more reliably than conventional coagulants made without gallium, itself a harmless addition.
The new material also resists converting to larger, less-reactive aggregates before it is used. This means it maintains a longer shelf life, avoiding the problem faced by related commercially available products that aggregate over time.
“The chemical substitution [of a gallium atom for an aluminum atom] has been studied by Sandia’s collaborators at the University of California at Davis, but nobody has ever put this knowledge to use in an application such as removing water contaminants like microorganisms,” said Nyman.
The project was conceived and all water treatment studies were performed at Sandia, said Nyman, who worked with Sandia microbiologist Tom Stewart. Transmission electron microscope images of bacteriophages binding to the altered material were achieved at the University of New Mexico. Mass spectroscopy of the alumina clusters in solution was performed at UC Davis.
The work was sponsored by Sandia’s Laboratory Directed Research Development office.
Adapted from materials provided by DOE/Sandia National Laboratories.

Ytterbium's Broken Symmetry: Largest Parity Violations Ever Observed In An Atom


ScienceDaily (July 22, 2009) — Ytterbium was discovered in 1878, but until it recently became useful in atomic clocks, the soft metal rarely made the news. Now ytterbium has a new claim to scientific fame. Measurements with ytterbium-174, an isotope with 70 protons and 104 neutrons, have shown the largest effects of parity violation in an atom ever observed – a hundred times larger than the most precise measurements made so far, with the element cesium.
“Parity” assumes that, on the atomic scale, nature behaves identically when left and right are reversed: interactions that are otherwise the same but whose spatial configurations are switched, as if seen in a mirror, ought to be indistinguishable. Sounds like common sense but, remarkably, this isn’t always the case.
“It’s the weak force that allows parity violation,” says Dmitry Budker, who led the research team. Budker is a member of the Nuclear Science Division at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory and a professor of physics at the University of California at Berkeley.
Of the four forces of nature – strong, electromagnetic, weak, and gravitational – the extremely short-range weak force was the last to be discovered. Neutrinos, having no electric charge, are immune to electromagnetism and only interact through the weak force. The weak force also has the startling ability to change the flavor of quarks, and to change protons into neutrons and vice versa.
Violating parity – neutrons and the weak force
Protons on their own last forever, apparently, but a free neutron falls apart in about 15 minutes; it turns into a proton by emitting an electron and an antineutrino, a process called beta decay. What makes beta decay possible is the weak force.
Scientists long assumed that nature, on the atomic scale, was symmetrical. It would look the same not only if left and right were reversed but also if the electrical charges of particles involved in an interaction were reversed, or even if the whole process ran backwards in time. Charge conjugation is written C, parity P, and time T; nature was thought to be C invariant, P invariant, and T invariant.
In 1957 researchers realized that the weak force didn’t play by the rules. When certain kinds of nuclei such as cobalt-60 are placed in a magnetic field to polarize them – line them up – and then allowed to undergo beta decay, they are more likely to emit electrons from their south poles than from their north poles.
This was the first demonstration of parity violation. Before the 1957 cobalt-60 experiment, renowned physicist Richard Feynman had said that if P violation were true – which he doubted – something long thought impossible would be possible after all: “There would be a way to distinguish right from left.”
It’s now apparent that many atoms exhibit parity violation, although it is not easy to detect. P violation has been measured with the greatest accuracy in cesium atoms, which have 55 protons and 78 neutrons in the nucleus, by using optical methods to observe the effect when atomic electrons are excited to higher energy levels.
The Berkeley researchers designed their own apparatus to detect the much larger parity violation predicted for ytterbium. In their experiment, ytterbium metal is heated to 500 degrees Celsius to produce a beam of atoms, which is sent through a chamber where magnetic and electric fields are oriented at right angles to each other. Inside the chamber the ytterbium atoms are hit by a laser beam, tuned to excite some of their electrons to higher energy states via a “forbidden” (highly unlikely) transition. The electrons then relax to lower energies along different pathways.
Weak interactions between the electron and the nucleus – plus weak interactions within the nucleus of the atom – act to mix some of the electron energy states together, making a small contribution to the forbidden transition. But other, more ordinary electromagnetic processes, which involve apparatus imperfections, also mix the states and blur the signal. The purpose of the chamber’s magnetic and electric fields is to amplify the parity-violation effect and to remove or identify these spurious electromagnetic effects.
Upon analyzing their data, the researchers found a clear signal for atomic parity violations, 100 times larger than the similar signal for cesium. With refinements to their experiment, the strength and clarity of the ytterbium signal promise significant advances in the study of weak forces in the nucleus.
Watching the weak force at work
The Budker group’s experiments are expected to expose how the weak charge changes in different isotopes of ytterbium, whose nuclei have the same number of protons but different numbers of neutrons, and will reveal how weak currents flow within these nuclei.
The results will also help explain how the neutrons in the nuclei of heavy atoms are distributed, including whether a “skin” of neutrons surrounds the protons in the center, as suggested by many nuclear models.
“The neutron skin is very hard to detect with charged probes, such as by electron scattering,” says Budker, “because the protons with their large electric charge dominate the interaction.”
He adds, “At a small level, the measured atomic parity violation effect depends on how the neutrons are distributed within the nucleus – specifically, their mean square radius. The mean square radius of the protons is well known, but this will be the first evidence of its kind for neutron distribution.”
Measurements of parity violation in ytterbium may also reveal “anapole moments” in the outer shell of neutrons in the nucleus (valence neutrons). As predicted by the Russian physicist Yakov Zel’dovich, these electric currents are induced by the weak interaction and circulate within the nucleus like the currents inside the toroidal winding of a tokamak; they have been observed in the valence protons of cesium but not yet in valence neutrons.
Eventually the experiments will lead to sensitive tests of the Standard Model – the theory that, although known to be incomplete, still best describes the interactions of all the subatomic particles so far observed.
“So far, the most precise data about the Standard Model has come from high-energy colliders,” says Budker. “The carriers of the weak force, the W and Z bosons, were discovered at CERN by colliding protons and antiprotons, a ‘high-momentum-transfer’ regime. Atomic parity violation tests of the Standard Model are very different – they’re in the low-momentum-transfer regime and are complementary to high-energy tests.”
Since 1957, when Zel’dovich first suggested seeking atomic variation in atoms by optical means, researchers have come ever closer to learning how the weak force works in atoms. Parity violation has been detected in many atoms, and its predicted effects, such as anapole moments in the valence protons of cesium, have been seen with ever-increasing clarity. With their new experimental techniques and the observation of a large atomic parity violation in ytterbium, Dmitry Budker and his colleagues have achieved a new landmark, moving closer to fundamental revelations about our asymmetric universe on the atomic scale.
Journal reference:
K. Tsigutkin, D. Dounas-Frazer, A. Family, J. E. Stalnaker, V. V. Yashchuck, and D. Budker. Observation of a large atomic parity violation in ytterbium. Physical Review Letters, (in press) [link]
Adapted from materials provided by DOE/Lawrence Berkeley National Laboratory.

Quantum Measurements: Common Sense Is Not Enough, Physicists Show


ScienceDaily (July 23, 2009) — In comparison to classical physics, quantum physics predicts that the properties of a quantum mechanical system depend on the measurement context, i.e. whether or not other system measurements are carried out. A team of physicists from Innsbruck, Austria, led by Christian Roos and Rainer Blatt, have for the first time proven in a comprehensive experiment that it is not possible to explain quantum phenomena in non-contextual terms.
The scientists report on their findings in the current issue of Nature.
Quantum mechanics describes the physical state of light and matter and formulates concepts that totally contradict the classical conception we have of nature. Thus, physicists have tried to explain non-causal phenomena in quantum mechanics by classical models of hidden variables, thereby excluding randomness, which is omnipresent in quantum theory. In 1967, however, the physicists Simon Kochen and Ernst Specker proved that measurements have to be contextual when explaining quantum phenomena by hidden variables. This means that the result of one measurement depends on which other measurements are performed simultaneously.
Interestingly, the simultaneous measurements here are compatible and do not disturb each other. The physicists led by Christian Roos and Rainer Blatt from the Institute of Quantum Optics and Quantum Information (IQOQI) of the Austrian Academy of Sciences and the University of Innsbruck have now been able to prove this proposition and rule out non-contextual explanations of quantum theory experimentally. In a series of measurements on a quantum system consisting of two ions they have shown that the measurement of a certain property is dependent on other measurements of the system.
Technological headstart
The experiment was carried out by the PhD students Gerhard Kirchmair and Florian Zähringer as well as Rene Gerritsma, a Dutch postdoc at the IQOQI. The scientists trapped a pair of laser-cooled calcium ions in an electromagnetic trap and carried out a series of measurements. „For this experiment we used techniques we had previously designed for building a quantum computer. We had to concatenate up to six quantum gates for this experiment", explains Christian Roos. „We were able to do this because, it is only recently that we can perform a quantum gate with high fidelity."
Only last year, a team of scientists led by Rainer Blatt realized an almost error-free quantum gate with a fidelity of 99 %. With this technological headstart, the scientists have now proven comprehensively in an experiment for the first time that the experimentally observed phenomena cannot be described by non-contextual models with hidden variables. The result is independent of the quantum state – it was tested in ten different states. Possible measurement disturbances could be ruled out by the experimental physicists with the help of theoreticians Otfried Gühne and Matthias Kleinmann from the group led by Prof. Hans Briegel at the IQOQI in Innsbruck.
Randomness cannot be excluded
In 1935 already, Albert Einstein, Boris Podolsky and Nathan Rosen questioned whether quantum mechanics theory is complete in the sense of a realistic physical theory – a criticism that is now well know in the scientific world as the EPR paradox. In the mid 1960s, John Bell showed that quantum theory cannot be a real and at the same time local theory, which, in the meantime, has also been proven experimentally. Kochen and Specker's results exclude other theoretical models but until now it was difficult to provide a convincing experimental proof. Following a proposition by the Spaniard Adán Cabello, the Innsbruck scientists have now successfully proven this point and produced unambiguous results experimentally. The physicists are supported by the Austrian Science Funds (FWF), the European Union, the Federation of Austrian Industry Tyrol, and Intelligence Advanced Research Projects Activity (IARPA).
Adapted from materials provided by University of Innsbruck, via EurekAlert!, a service of AAAS.

mercoledì 22 luglio 2009

'Lab On A Chip' To Give Growers Real-time Glimpse Into Water Stress In Plants


ScienceDaily (July 22, 2009) — Fifteen years ago, when Alan Lakso first sought to enlist Cornell's nanofabrication laboratory to develop a tiny sensor that would measure water stress in grapevines, the horticultural sciences professor ended up back at the drawing board.
It wasn't until Abraham Stroock, associate professor of chemical engineering, had a breakthrough of his own that Lakso's vision began to take shape. Stroock's lab recently developed a synthetic tree that mimics the flow of water inside plants using a slab of hydrogel with nanometer-scale pores. At last Lakso had access to the technology to move forward.
The device is an embedded microsensor capable of measuring real-time water stress in living plants. In theory, the sensor will help vintners strike the precise balance between drought and overwatering -- both of which diminish the quality of wine grapes.
"To manage for optimum stress," said Lakso, a researcher at the New York State Agricultural Experiment Station in Geneva, "we need to monitor ... exactly what's going on in the vine."
With Vinay Pagay, a graduate student with degrees in computer engineering and viticulture, the team is working at the Cornell Nanofabrication Facility in Ithaca to develop 4-inch diameter silicon wafer protoypes, each containing approximately 100 microsensors. They have also begun collaborating with Infotonics, a firm in Canandaigua, N.Y., that specializes in microelectromechanical systems (MEMS), to plan commercialization of the sensors. The partnership applies cutting-edge engineering to practical agricultural concerns.
The team hopes to design a sensor that will transmit field readings wirelessly to a central server; the data will then be summarized online for the grower. The concept has already received attention from E. & J. Gallo Winery in California as well as researchers and industry leaders from Australia, Spain and Italy. "It's not just for the big growers," Lakso said. "We hope the micro-manufacturing will provide low-cost sensors for small growers as well."
Looking ahead, the team is pursuing alternative sensors that could enhance research in fields from food science to forestry. They have begun development of a "multi-use sensor" that redirects water flow inside the plant through a shunt. In this case, the sensor could measure the flow of water and mineral nutrients through the plant, in addition to water stress. Pagay described it as "a lab on a chip."
Beyond winemaking, the technology has implications for manufacturing, food processing and electronics. Team member Taryn Bauerle, assistant professor of horticulture, described how such sensors could be implanted throughout trees in a forest ecosystem to measure water use and nutrient flow on a large scale with unprecedented accuracy. "All of these [researchers'] brains are coming together," she said. "There's no limit to where we can take this type of technology."
Adapted from materials provided by Cornell University.

Lighting Revolution Forecast By Top Scientist


ScienceDaily (July 22, 2009) — New developments in a substance which emits brilliant light could lead to a revolution in lighting for the home and office in five years, claims a leading UK materials scientist, Professor Colin Humphreys of Cambridge University. The source of the huge potential he foresees, gallium nitride (GaN), is already used for some lighting applications such as camera flashes, bicycle lights, mobile phones and interior lighting for buses, trains and planes.
But making it possible to use GaN for home and office lighting is the Holy Grail. If achieved, it could reduce the typical electricity consumption for lighting of a developed country by around 75% while delivering major cuts in carbon dioxide emissions from power stations, and preserving fossil fuel reserves.
‘GaN LEDs have a very exciting future' says Professor Humphreys. ‘In particular they are incredibly long lasting. A GaN LED can burn for 100,000hours - one hundred times longer than a conventional light bulb. In practice this means it only needs replacing after 60 years of normal household use. Also, unlike the energy-saving compact fluorescent lights now in use, GaN LEDs don't contain mercury so disposal is not such an environmental headache.'
But to unlock these benefits, important barriers need to be tackled by scientists. GaN LEDs are too expensive to manufacture for wide scale deployment in homes and workplaces. And the harsh quality of the light produced is another limiting factor. At the Cambridge Centre for Gallium Nitride where Professor Humphreys leads the research, a detailed new theory that explains the mystery of why GaN emits light so strongly has recently been developed in collaboration with Professor Phil Dawson of Manchester University. ‘
Such understanding is vital to improving GaN lighting's quality and efficiency' says Professor Humphreys. ‘Our centre is also working on an innovative technique for growing GaN on six-inch diameter silicon wafers, rather than the sapphire wafers used to date. This could deliver a tenfold reduction in manufacturing costs and so help GaN lighting penetrate new markets'. Another of the centre's projects is investigating how GaN lighting could be made to mimic sunlight which could have important benefits for sufferers of Seasonal Affective Disorder (SAD).
‘GaN lighting should start making its mark in homes and offices within about five years', predicts Professor Humphreys. ‘That won't just be good news for the environment - it will also benefit consumers in terms of convenience, electricity bills and quality of life.'
Looking further ahead, the possibilities for GaN light appear wide-ranging. Currently, GaN LEDs are phosphor -coated to transform the light from blue into white. But there could be scope to remove the coating and incorporate mini LEDs, each producing a different colour, in the overall ‘light bulb'. Together the mini LEDs would produce white light, but people in the home or office could alter the precise balance, for example to a bluish light, to suit their mood. ‘This and other applications, for example in healthcare for detecting tumours, and water treatment for developing countries, might be achievable in 10 years', says Professor Humphreys.
Adapted from materials provided by AlphaGalileo Foundation, via AlphaGalileo.