Freedawn Scientia: January 2015

Friday 23 January 2015

NASA, Microsoft Collaboration Will Allow Scientists to ‘Work on Mars’

NASA and Microsoft have teamed up to develop software called OnSight, a new technology that will enable scientists to work virtually on Mars using wearable technology called Microsoft HoloLens.

New NASA software called OnSight will use holographic computing to overlay visual information and data from the agency’s Mars Curiosity Rover into the user’s field of view. Holographic computing blends a view of the physical world with computer-generated imagery to create a hybrid of real and virtual.
Image Credit:
NASA

Developed by NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, OnSight will give scientists a means to plan and, along with the Mars Curiosity rover, conduct science operations on the Red Planet.

“OnSight gives our rover scientists the ability to walk around and explore Mars right from their offices,” said Dave Lavery, program executive for the Mars Science Laboratory mission at NASA Headquarters in Washington. “It fundamentally changes our perception of Mars, and how we understand the Mars environment surrounding the rover.”

OnSight will use real rover data and extend the Curiosity mission’s existing planning tools by creating a 3-D simulation of the Martian environment where scientists around the world can meet. Program scientists will be able to examine the rover’s worksite from a first-person perspective, plan new activities and preview the results of their work firsthand.

“We believe OnSight will enhance the ways in which we explore Mars and share that journey of exploration with the world,” said Jeff Norris, JPL’s OnSight project manager.

Until now, rover operations required scientists to examine Mars imagery on a computer screen, and make inferences about what they are seeing. But images, even 3-D stereo views, lack a natural sense of depth that human vision employs to understand spatial relationships.

The OnSight system uses holographic computing to overlay visual information and rover data into the user’s field of view. Holographic computing blends a view of the physical world with computer-generated imagery to create a hybrid of real and virtual.

To view this holographic realm, members of the Curiosity mission team don a Microsoft HoloLens device, which surrounds them with images from the rover’s Martian field site. They then can stroll around the rocky surface or crouch down to examine rocky outcrops from different angles. The tool provides access to scientists and engineers looking to interact with Mars in a more natural, human way.

“Previously, our Mars explorers have been stuck on one side of a computer screen. This tool gives them the ability to explore the rover’s surroundings much as an Earth geologist would do field work here on our planet,” said Norris.

The OnSight tool also will be useful for planning rover operations. For example, scientists can program activities for many of the rover’s science instruments by looking at a target and using gestures to select menu commands.

The joint effort to develop OnSight with Microsoft grew from an ongoing partnership to investigate advances in human-robot interaction. The JPL team responsible for OnSight specializes in systems to control robots and spacecraft. The tool will assist researchers in better understanding the environment and workspace of robotic spacecraft — something that can be quite challenging with their traditional suite of tools.

JPL plans to begin testing OnSight in Curiosity mission operations later this year. Future applications may include Mars 2020 rover mission operations, and other applications in support of NASA’s journey to Mars.

JPL manages the Mars Science Laboratory Project for NASA’s Science Mission Directorate in Washington, and built the project’s Curiosity rover.

– Credit and Resource –

Provided by NASA

NASA, Microsoft Collaboration Will Allow Scientists to ‘Work on Mars’

Exotic, gigantic molecules fit inside each other like Russian nesting dolls

University of Chicago scientists have experimentally observed for the first time a phenomenon in ultracold, three-atom molecules predicted by Russian theoretical physicist Vitaly Efimov in 1970.

Sizes of triatomic molecules that follow the geometrical scaling predicted by Vitaly Efimov in 1970. University of Chicago physicists have reported evidence of this geometric scaling in three-atom, lithium-ceisum Efimov molecules at a temperature 200 nanokelvin, a fraction of a degree above absolute zero (minus 459.6 degrees Fahreneheit). Credit: Cheng Chin group, University of Chicago

In this quantum phenomenon, called geometric scaling, the triatomic molecules fit inside one another like an infinitely large set of Russian nesting dolls.

“This is a new rule in chemistry that molecular sizes can follow a geometric series, like 1, 2, 4, 8…,” said Cheng Chin, professor in physics. “In our case, we find three molecular states in this sequence where one molecular state is about 5 times larger than the previous one.”

Chin and four members of his research group published their findings Dec. 9, 2014, in Physical Review Letters.

“Quantum theory makes the existence of these gigantic molecules inevitable, provided proper—and quite challenging—conditions are created,” said Efimov, now at the University of Washington.

The UChicago team observed three molecules in the series, consisting of one lithium atom and two cesium atoms in a vacuum chamber at the ultracold temperature of approximately 200 nanokelvin, a tiny fraction of a degree above absolute zero (minus 459.6 degrees Fahrenheit).

Infinitely large molecules

Given an infinitely large universe, the number of increasingly larger molecules in this cesium-lithium system also would extend to infinity. This remarkable idea stems from the exotic nature of quantum mechanics, which confirms to different laws of physics than those that govern the universe on a macroscopic scale.

“These are certainly exotic molecules,” said Shih-Kuang Tung, the postdoctoral scholar, now at Northwestern University, who led the project. Only under strict conditions could Tung and his colleagues see the geometric scaling in their Efimov molecules. It appears that neither two-atom nor four-atom molecules can achieve the Efimov state. “There’s a special case for three atoms,” Chin said.

Efimov’s reaction to the research was twofold. “First, I am amazed by the predictive power of the quantum theory,” he said. “Second, I am amazed by the skill of the experimentalists who managed to create those challenging conditions.”

The finding is important because it shows that Efimov molecules, like other complex phenomena in nature, follow a simple mathematical rule. One other example in nature that displays geometric scaling is snowflakes, rooted in the microscopic physics of their hexagonal crystal structure.

A team at the University of Innsbruck in Austria, which included Chin, experimentally observed the first Efimov molecular state in 2006 in molecules consisting of three cesium atoms. In this Efimov state, three cesium atoms become entangled at temperatures slightly above absolute zero. They form a Borromean ring of three interlocking circles. Any two of them, however, will not interlock.

Scaling factor

“The difficulty is that based on what we understand of Efimov’s theory, the scaling factor is predicted to be 22.7 for the cesium system, which is a very large number,” explained Chin, who also is a member of UChicago’s James Franck and Enrico Fermi institutes. Scaling at such a large value demands an extremely low temperature, challenging to reach experimentally.

But the scaling factor of the lithium-cesium triatomic molecule was predicted to be more manageable of 4.8. Indeed, after setting up their experiment, “We were able to see three of them at a more accessible temperature of 200 nano-Kelvin,” Chin said. “Their sizes are measured to be 17, 86 and 415 nano-meters, respectively. They closely follow a geometric progression with the predicted scaling factor.”

But even the lithium-cesium system presented a difficulty: the significantly differing masses of the two elements, which was critical for observing multiple Efimov states. Lithium is one of the lightest elements on the periodic table, while cesium is quite heavy. “One is really massive compared to the other,” Tung said.

He compared working both elements into an ultracold experiment to dangling a monkey and an elephant from springs. They would hang at different levels, but still needed to interact.

In the experiment, the UChicago physicists lowered the temperatures of the lithium and cesium atoms separately, then brought them together to form the triatomic, Efimov molecules.

“It’s a very complicated experiment,” Tung said, one requiring an ultracold experimental tool called Feshbach resonance. Carried out in a magnetic field, Feshbach resonance allowed researchers to bind and control the interactions between the cesium and lithium atoms.

Cold atoms are subject to manipulation via Feshbach resonance, which allows the observation of geometric scaling. “Feshbach resonance is a really important tool for us,” Tung said. He and his associates learned how to wield the tool effectively in the past three years.

“We needed to tune the Feshbach resonances very carefully in order to generate these Efimov molecules,” Tung said.

The efforts culminated in experimental success. Efimov said the results made him feel like the parent of a successful child. “The parent is proud of the child’s achievement, and he is also proud that in a sense he is part of the child’s success.”

– Credit and Resource –

More information: “Geometric Scaling of Efimov States in a 6Li-133Cs Mixture,” by Shih-Kuang Tung, Karina Jiménez-García, Jacob Johansen, Colin V. Parker, and Cheng Chin, Physical Review Letters, DOI: dx.doi.org/10.1103/PhysRevLett.113.240402

Provided by University of Chicago

Exotic, gigantic molecules fit inside each other like Russian nesting dolls

Bose-Einstein condensate could be used to observe quantum mass acquisition

A possible means of observing an exotic quantum effect that imparts mass to a normally massless particle has been proposed by researchers from the RIKEN Center for Emergent Matter Science.

Bose–Einstein condensates could be used as a quantum simulator to study the phenomenon of quantum mass acquisition. Credit: agsandrew/iStock/Thinkstock

At temperatures close to absolute zero, atoms can start to form a collective state known as a Bose–Einstein condensate (BEC). Scientists have found that this state of matter is useful as a ‘quantum simulator’ for investigating particles that have been predicted to exist by theory but are too difficult to create or observe directly.

“Quantum simulators are very versatile, allowing interactions, particle density and temperature to be tuned,” says Masahito Ueda from the RIKEN research team. “The pressing issue in this field is to look for something very fundamental that can be demonstrated for the first time in such atomic gases.”

Through mathematical modeling, Ueda and his colleagues Nguyen Thanh Phuc from RIKEN and Yuki Kawaguchi from the University of Tokyo showed that a BEC could be used to simulate a so-far-unobserved phenomenon known as quantum mass acquisition. This effect causes a normally massless elementary particle called a quasi-Nambu–Goldstone boson to acquire mass as a result of minute quantum fluctuations. Researchers believe that this effect could appear in superfluids, superconductors and some magnetic materials. Yet quantum mass acquisition has never been seen because the effect is too small to be distinguished from other secondary effects.

“Extremely minute quantum phenomena are amplified to a macroscopic level in BECs and therefore made visible,” says Ueda. The researchers’ analysis shows that the emergent energy gap of the quasi-Nambu–Goldstone boson in a BEC is two orders of magnitude larger than the zero-point energy of the system. This means that the state is much more robust than previously thought, raising the hope that it might be possible to experimentally observe the quasi-Nambu–Goldstone boson and quantum mass acquisition.

The choice of atom in the gas is crucial for observing quantum mass acquisition. Many BECs are made using helium atoms and spin-polarized alkali atoms, which are spinless. Ueda and his team have shown that atoms with spin ‘degrees of freedom’ are required to observe quantum mass acquisition. Such a ‘spinor’ BEC could be created using rubidium atoms.

“Our work demonstrates that fundamental physical phenomena that can usually only be tested using particle accelerators, can be reproduced on the tabletop,” says Ueda. “We now plan to explore what other fundamental phenomena can be revealed in atomic BECs.”

– Credit and Resources –

More information: Phuc, N. T., Kawaguchi, Y. & Ueda, M. “Quantum mass acquisition in spinor Bose-Einstein condensates.” Physical Review Letters 113, 230401 (2014). DOI: 10.1103/PhysRevLett.113.230401

Provided by RIKEN

Bose-Einstein condensate could be used to observe quantum mass acquisition

Scientists set quantum speed limit

University of California, Berkeley, scientists have proved a fundamental relationship between energy and time that sets a “quantum speed limit” on processes ranging from quantum computing and tunneling to optical switching.

The speed limit, that is, the minimal time to transition between two easily distinguishable states, such as the north and south poles representing up and down states of a quantum spin (top), is characterized by a well-known relationship. But the speed limit between two states not entirely distinguishable, which correspond to states of arbitrary latitude and longitude whether on or within the sphere of all possible states of a quantum spin (bottom), was unknown until two UC Berkeley chemical physicists calculated it. Credit: Ty Volkoff image, UC Berkeley.

The energy-time uncertainty relationship is the flip side of the Heisenberg uncertainty principle, which sets limits on how precisely you can measure position and speed, and has been the bedrock of quantum mechanics for nearly 100 years. It has become so well-known that it has infected literature and popular culture with the idea that the act of observing affects what we observe.

Not long after German physicist Werner Heisenberg, one of the pioneers of quantum mechanics, proposed his relationship between position and speed, other scientists deduced that energy and time were related in a similar way, implying limits on the speed with which systems can jump from one energy state to another. The most common application of the energy-time uncertainty relationship has been in understanding the decay of excited states of atoms, where the minimum time it takes for an atom to jump to its ground state and emit light is related to the uncertainty of the energy of the excited state.

“This is the first time the energy-time uncertainty principle has been put on a rigorous basis – our arguments don’t appeal to experiment, but come directly from the structure of quantum mechanics,” said chemical physicist K. Birgitta Whaley, director of the Berkeley Quantum Information and Computation Center and a UC Berkeley professor of chemistry. “Before, the principle was just kind of thrown into the theory of quantum mechanics.”

The new derivation of the energy-time uncertainty has application for any measurement involving time, she said, particularly in estimating the speed with which certain quantum processes – such as calculations in a quantum computer – will occur.

“The uncertainty principle really limits how precise your clocks can be,” said first author Ty Volkoff, a graduate student who just received his Ph.D. in chemistry from UC Berkeley. “In a quantum computer, it limits how fast you can go from one state to the other, so it puts limits on the clock speed of your computer.”

The new proof could even affect recent estimates of the computational power of the universe, which rely on the energy-time uncertainty principle.

Volkoff and Whaley included the derivation of the uncertainty principle in a larger paper devoted to a detailed analysis of distinguishable quantum states that appeared online Dec. 18 in the journal Physical Review A.

The problem of precision measurement

Heisenberg’s uncertainty principle, proposed in 1927, states that it’s impossible to measure precisely both the position and speed – or more properly, momentum – of an object. That is, the uncertainty in measurement of the position times the uncertainty in measurement of momentum will always be greater than or equal to Planck’s constant. Planck’s constant is an extremely small number (6.62606957 × 10-34 square meter-kilogram/second) that describes the graininess of space.

To physicists, an equally useful principle relates the uncertainties of measuring both time and energy: The variance of the energy of a quantum state times the lifetime of the state cannot be less than Planck’s constant.

“When students first learn about time-energy uncertainty, they learn about the lifetime of atomic states or emission line widths in spectroscopy, which are very physical but empirical notions,” Volkoff said.

This observed relationship was first addressed mathematically in a 1945 paper by two Russian physicists who dealt only with transitions between two obviously distinct energy states. The new analysis by Volkoff and Whaley applies to all types of experiments, including those in which the beginning and end states may not be entirely distinct. The analysis allows scientists to calculate how long it will take for such states to be distinguishable from one another at any level of certainty.

“In many experiments that examine the time evolution of a quantum state, the experimenters are dealing with endpoints where the states are not completely distinguishable,” Volkoff said. “But you couldn’t determine the minimum time that process would take from our current understanding of the energy-time uncertainty.”

Most experiments dealing with light, as in the fields of spectroscopy and quantum optics, involve states that are not entirely distinct, he said. These states evolve on time scales of the order of femtoseconds – millionths of a billionth of a second.

Alternatively, scientists working on quantum computers aim to establish entangled quantum states that evolve and perform a computation with speeds on the order of nanoseconds.

“Our analysis reveals that a minimal finite length of time must elapse in order to achieve a given success rate for distinguishing an initial quantum state from its time-evolved image using an optimal measurement,” Whaley said.

The new analysis could help determine the times required for quantum tunneling, such as the tunneling of electrons through the band-gap of a semiconductor or the tunneling of atoms in biological proteins.

It also could be useful in a new field called “weak measurement,” which involves tracking small changes in a quantum system, such as entangled qubits in a quantum computer, as the system evolves. No one measurement sees a state that is purely distinct from the previous state.

– Credit and Resources –

More information: Macroscopicity of quantum superpositions on a one-parameter unitary path in Hilbert space (PhysRevA) journals.aps.org/pra/abstract/… 3/PhysRevA.90.062122

Provided by University of California – Berkeley

Scientists set quantum speed limit

Three extremely luminous gamma-ray sources discovered in Milky Way's satellite galaxy

The High Energy Stereoscopic System, H.E.S.S., has demonstrated its excellent capabilities. In the Large Magellanic Cloud, it discovered most luminous very high-energy gamma-ray sources: three objects of different type, namely the most powerful pulsar wind nebula, the most powerful supernova remnant, and a shell of 270 light years in diameter blown by multiple stars, and supernovae – a so-called superbubble. This is the first time that stellar-type gamma-ray sources are detected in an external galaxy, at these gamma-ray energies. The superbubble represents a new source class in very high-energy gamma rays.

Optical image of the Milky Way and a multi-wavelength (optical, Hα) zoom into the Large Magellanic Cloud with superimposed H.E.S.S. sky maps. Credit: Milky Way image: © H.E.S.S. Collaboration, optical: SkyView, A. Mellinger; LMC image: © H.E.S.S. Collaboration, Hα: R. Kennicutt, J.E. Gaustad et al. (2001), optical (B-band): G. Bothun

Very high-energy gamma rays are the best tracers of cosmic accelerators such as supernova remnants and pulsar wind nebulae – end-products of massive stars. There, charged particles are accelerated to extreme velocities. When these particles encounter light or gas in and around the cosmic accelerators, they emit gamma rays. Very high-energy gamma rays can be measured on Earth by observing the Cherenkov light emitted from the particle showers produced by incident gamma rays high up in the atmosphere using large telescopes with fast cameras.

The Large Magellanic Cloud (LMC) is a dwarf satellite galaxy of our Milky Way, located about 170.000 light years away and showing us its face. New, massive stars are formed at a high rate in the LMC, and it harbors numerous massive stellar clusters. The LMC’s supernova rate relative to its stellar mass is five times that of our Galaxy. The youngest supernova remnant in the local group of galaxies, SN 1987A, is also a member of the LMC. Therefore, the H.E.S.S. scientists dedicated significant observation to searching for very high-energy gamma rays from this cosmic object.

For a total of 210 hours, the High Energy Stereoscopic System (H.E.S.S.) has observed the largest star-forming region within the LMC called Tarantula Nebula. For the first time in a galaxy outside the Milky Way, individual sources of very high-energy gamma rays could be resolved: three extremely energetic objects of different type.

The so-called superbubble 30 Dor C is the largest known X-ray-emitting shell and appears to have been created by several supernovae and strong stellar winds. Superbubbles are broadly discussed as (complementary or alternative to individual supernova remnants) factories where the galactic cosmic rays are produced. The H.E.S.S. results demonstrate that the bubble is a source of, and filled by, highly energetic particles. The superbubble represents a new class of sources in the very high-energy regime.

Pulsars are highly magnetized, fast rotating neutron stars that emit a wind of ultra-relativistic particles forming a nebula. The most famous one is the Crab Nebula, one of the brightest sources in the high-energy gamma-ray sky. The pulsar PSR J0537−6910 driving the wind nebula N 157B discovered by the H.E.S.S. telescopes in the LMC is in many respects a twin of the very powerful Crab pulsar in our own Galaxy. However, its pulsar wind nebula N 157B outshines the Crab Nebula by an order of magnitude, in very high-energy gamma rays. Reasons are the lower magnetic field in N 157B and the intense starlight from neighboring star-forming regions, which both promote the generation of high-energy gamma rays.

The supernova remnant N 132D, known as a bright object in the radio and infrared bands, appears to be one of the oldest – and strongest – supernova remnants still glowing in very high-energy gamma rays. Between 2500 and 6000 years old – an age where models predict that the supernova explosion front has slowed down and it ought no longer be efficiently accelerating particles – it still outshines the strongest supernova remnants in our Galaxy. The observations confirm suspicions raised by other H.E.S.S. observations, that supernova remnants can be much more luminous than thought before.

Observed at the limits of detectability, and partially overlapping with each other, these new sources challenged the H.E.S.S. scientists. The discoveries were only possible due to the development of advanced methods of interpreting the Cherenkov images captured by the telescopes, improving in particular the precision with which gamma-ray directions can be determined.

“Both the pulsar wind nebula and the supernova remnant, detected in the Large Magellanic Cloud by H.E.S.S., are more energetic than their most powerful relatives in the Milky Way. Obviously, the high star formation rate of the LMC causes it to breed very extreme objects”, summarizes Chia Chun Lu, a student who analyzed the LMC data as her thesis project. “Surprisingly, however, the young supernova remnant SN 1987A did not show up, in contrast to theoretical predictions. But we’ll continue the search for it,” adds her advisor Werner Hofmann, director at the MPI for Nuclear Physics in Heidelberg and for many years H.E.S.S. spokesperson.

Indeed, the new H.E.S.S. II 28 m telescope will boost performance of the H.E.S.S. telescope system, and in the more distant future the planned Cherenkov Telescope Array (CTA) will provide even deeper and higher-resolution gamma-ray images of the LMC – in the plans for science with CTA, the satellite galaxy is already identified as a “Key Science Project” deserving special attention.

The H.E.S.S. Telescopes

The collaboration: The High Energy Stereoscopic System (H.E.S.S.) team consists of scientists from Germany, France, the United Kingdom, Namibia, South Africa, Ireland, Armenia, Poland, Australia, Austria, the Netherlands and Sweden, supported by their respective funding agencies and institutions.

The instrument: The results were obtained using the High Energy Stereoscopic System (H.E.S.S.) telescopes in Namibia, in South-West Africa. This system of four 13 m diameter telescopes – recently complemented with the huge 28 m H.E.S.S. II telescope – is one of the most sensitive detectors of very high-energy gamma rays. These are absorbed in the atmosphere, where they create a short-lived shower of particles. The H.E.S.S. telescopes detect the faint, short flashes of bluish light which these particles emit (named Cherenkov light, lasting a few billionths of a second), collecting the light with big mirrors which reflect onto extremely sensitive cameras. Each image gives the position on the sky of a single gamma-ray photon, and the amount of light collected gives the energy of the initial gamma ray. Building up the images photon by photon allows H.E.S.S. to create maps of astronomical objects as they appear in gamma rays.

The H.E.S.S. telescopes have been operating since late 2002; in September 2012 H.E.S.S. celebrated the first decade of operation, by which time the telescopes had recorded 9415 hours of observations, and detected 6361 million air shower events. H.E.S.S. has discovered the majority of the about 150 known cosmic objects emitting very high-energy gamma rays. In 2006, the H.E.S.S. team was awarded the Descartes Prize of the European Commission, in 2010 the Rossi Prize of the American Astronomical Society. A study performed in 2009 listed H.E.S.S. among the top 10 observatories worldwide.

– Credit and Resource –

More information: “The exceptionally powerful TeV γ-ray emitters in the Large Magellanic Cloud” Science 23 January 2015: Vol. 347 no. 6220 pp. 406-412 DOI: 10.1126/science.1261313

Provided by H.E.S.S.

Three extremely luminous gamma-ray sources discovered in Milky Way's satellite galaxy

Physicists find a new way to slow the speed of light

A team of physicists working at the University of Glasgow has found a way to slow the speed of light that does not involve running it through a medium such as glass or water. Instead, as they explain in their paper published in the journal Science, they caused a change in the speed by first running it through a mask, which changed its shape.

Everyone knows that the speed of light in a vacuum is constant, but now it appears that there is a way to indirectly alter its speed—by running it through a special mask. Doing so apparently causes a change to the shape of the photon, making it move through a vacuum slower than an unaltered photon.

The researchers built what they called a racetrack—setting up a dual course for firing photons and detecting when they struck a detector a meter away. The first group of photons was fired in the normal way, while the second group was fired through a filter to shape it into either a Gaussian or Bessel beam. The photons from both groups were launched at the same time but the unshaped photons beat the shape-altered photons to the finish line by approximately 0.001 percent. There were two reasons for that. The first was that moving through the filter slowed the photons, much as would happen were they to pass through other mediums such as water or glass. The second reason was more complex, because it demonstrated that the speed of the photons was slower than normal after passing through the filter—light is supposed to speed back up to its normal constant after passing through a medium. The experiment showed that light can be caused to travel slower than c, by changing its shape.

The researchers explain this result by noting that they were using group velocity to measure the light’s speed—a measurement of the group’s envelope speed. The mask, they explain, caused some of the photons in the group to move at a slight angle to the other’s causing a slowdown for the group as a whole. Thus, their results are not going to upend one of the basic tenets of modern physics, it is more likely that future researchers will have to make sure lab or astronomical observations are not being impacted by shape changes that occur naturally.

University of Glasgow press release

Scientists have long known that the speed of light can be slowed slightly as it travels through materials such as water or glass. However, it has generally been thought impossible for particles of light, known as photons, to be slowed as they travel through free space, unimpeded by interactions with any materials.

In a new paper published in Science Express today (Friday 23 January), researchers from the University of Glasgow and Heriot-Watt University describe how they have managed to slow photons in free space for the first time. They have demonstrated that applying a mask to an optical beam to give photons a spatial structure can reduce their speed.

Their experiment was configured like a race, with two photons released simultaneously across identical distances towards a defined finish line.

The team compare a beam of light, containing many photons, to a team of cyclists who share the work by taking it in turns to cycle at the front. Although the group travels along the road as a unit, the speed of individual cyclists can vary as they swap position.

The group formation can make it difficult to define a single velocity for all cyclists, and the same applies to light. A single pulse of light contains many photons, and scientists know that light pulses are characterised by a number of different velocities.

The researchers found that one photon reached the finish line as predicted, but the structured photon which had been reshaped by the mask arrived later, meaning it was travelling more slowly in free space. Over a distance of one metre, the team measured a slowing of up to 20 wavelengths, many times greater than the measurement precision.

The work demonstrates that, after passing the light beam through a mask, photons move more slowly through space. Crucially, this is very different to the slowing effect of passing light through a medium such as glass or water, where the light is only slowed during the time it is passing through the material – it returns to the speed of light after it comes out the other side. The effect of passing the light through the mask is to limit the top speed at which the photons can travel.

The work was carried out by a team from the University of Glasgow’s Optics Group, led by Professor Miles Padgett, working with theoretical physicists led by Stephen Barnett, and in partnership with Daniele Faccio from Heriot-Watt University.

Daniel Giovannini, one of the lead authors of the paper, said: “The delay we’ve introduced to the structured beam is small, measured at several micrometres over a propagation distance of one metre, but it is significant. We’ve measured similar effects in two different types of beams known as Bessel beams and Gaussian beams.”

Co-lead author Jacquiline Romero said: “We’ve achieved this slowing effect with some subtle but widely-known optical principles. This finding shows unambiguously that the propagation of light can be slowed below the commonly accepted figure of 299,792,458 metres per second, even when travelling in air or vacuum.

“Although we measure the effect for a single photon, it applies to bright light beams too. The effect is biggest when the lenses used to create the beam are large and when the distance over which the light is focused is small, meaning the effect only applies at short range.”

Professor Padgett added: “It might seem surprising that light can be made to travel more slowly like this, but the effect has a solid theoretical foundation and we’re confident that our observations are correct.

“The results give us a new way to think about the properties of light and we’re keen to continue exploring the potential of this discovery in future applications. We expect that the effect will be applicable to any wave theory, so a similar slowing could well be created in sound waves, for example.”

The team’s paper, titled ‘Spatially Structured Photons that Travel in Free Space Slower than the Speed of Light’, is published in Science Express, which provides electronic publication of selected papers in advance of print in the journal Science.

– Credit and Resource –

More information: Spatially structured photons that travel in free space slower than the speed of light, Science, DOI: 10.1126/science.aaa3035

Physicists find a new way to slow the speed of light

Telomere extension turns back aging clock in cultured human cells

A new procedure can quickly and efficiently increase the length of human telomeres, the protective caps on the ends of chromosomes that are linked to aging and disease, according to scientists at the Stanford University School of Medicine.

Human chromosomes (grey) capped by telomeres (white). Credit: PD-NASA; PD-USGOV-NASA

Treated cells behave as if they are much younger than untreated cells, multiplying with abandon in the laboratory dish rather than stagnating or dying.

The procedure, which involves the use of a modified type of RNA, will improve the ability of researchers to generate large numbers of cells for study or drug development, the scientists say. Skin cells with telomeres lengthened by the procedure were able to divide up to 40 more times than untreated cells. The research may point to new ways to treat diseases caused by shortened telomeres.

Telomeres are the protective caps on the ends of the strands of DNA called chromosomes, which house our genomes. In young humans, telomeres are about 8,000-10,000 nucleotides long. They shorten with each cell division, however, and when they reach a critical length the cell stops dividing or dies. This internal “clock” makes it difficult to keep most cells growing in a laboratory for more than a few cell doublings.

‘Turning back the internal clock’

“Now we have found a way to lengthen human telomeres by as much as 1,000 nucleotides, turning back the internal clock in these cells by the equivalent of many years of human life,” said Helen Blau, PhD, professor of microbiology and immunology at Stanford and director of the university’s Baxter Laboratory for Stem Cell Biology. “This greatly increases the number of cells available for studies such as drug testing or disease modeling.”

A paper describing the research was published today in the FASEB Journal. Blau, who also holds the Donald E. and Delia B. Baxter Professorship, is the senior author. Postdoctoral scholar John Ramunas, PhD, of Stanford shares lead authorship with Eduard Yakubov, PhD, of the Houston Methodist Research Institute.

The researchers used modified messenger RNA to extend the telomeres. RNA carries instructions from genes in the DNA to the cell’s protein-making factories. The RNA used in this experiment contained the coding sequence for TERT, the active component of a naturally occurring enzyme called telomerase. Telomerase is expressed by stem cells, including those that give rise to sperm and egg cells, to ensure that the telomeres of these cells stay in tip-top shape for the next generation. Most other types of cells, however, express very low levels of telomerase.

Transient effect an advantage

The newly developed technique has an important advantage over other potential methods: It’s temporary. The modified RNA is designed to reduce the cell’s immune response to the treatment and allow the TERT-encoding message to stick around a bit longer than an unmodified message would. But it dissipates and is gone within about 48 hours. After that time, the newly lengthened telomeres begin to progressively shorten again with each cell division.

The transient effect is somewhat like tapping the gas pedal in one of a fleet of cars coasting slowly to a stop. The car with the extra surge of energy will go farther than its peers, but it will still come to an eventual halt when its forward momentum is spent. On a biological level, this means the treated cells don’t go on to divide indefinitely, which would make them too dangerous to use as a potential therapy in humans because of the risk of cancer.

The researchers found that as few as three applications of the modified RNA over a period of a few days could significantly increase the length of the telomeres in cultured human muscle and skin cells. A 1,000-nucleotide addition represents a more than 10 percent increase in the length of the telomeres. These cells divided many more times in the culture dish than did untreated cells: about 28 more times for the skin cells, and about three more times for the muscle cells.

“We were surprised and pleased that modified TERT mRNA worked, because TERT is highly regulated and must bind to another component of telomerase,” said Ramunas. “Previous attempts to deliver mRNA-encoding TERT caused an immune response against telomerase, which could be deleterious. In contrast, our technique is nonimmunogenic. Existing transient methods of extending telomeres act slowly, whereas our method acts over just a few days to reverse telomere shortening that occurs over more than a decade of normal aging. This suggests that a treatment using our method could be brief and infrequent.”

Potential uses for therapy

“This new approach paves the way toward preventing or treating diseases of aging,” said Blau. “There are also highly debilitating genetic diseases associated with telomere shortening that could benefit from such a potential treatment.”

Blau and her colleagues became interested in telomeres when previous work in her lab showed that the muscle stem cells of boys with Duchenne muscular dystrophy had telomeres that were much shorter than those of boys without the disease. This finding not only has implications for understanding how the cells function—or don’t function—in making new muscle, but it also helps explain the limited ability to grow affected cells in the laboratory for study.

The researchers are now testing their new technique in other types of cells.

“This study is a first step toward the development of telomere extension to improve cell therapies and to possibly treat disorders of accelerated aging in humans,” said John Cooke, MD, PhD. Cooke, a co-author of the study, formerly was a professor of cardiovascular medicine at Stanford. He is now chair of cardiovascular sciences at the Houston Methodist Research Institute.

“We’re working to understand more about the differences among cell types, and how we can overcome those differences to allow this approach to be more universally useful,” said Blau, who also is a member of the Stanford Institute for Stem Cell Biology and Regenerative Medicine.

“One day it may be possible to target muscle stem cells in a patient with Duchenne muscular dystrophy, for example, to extend their telomeres. There are also implications for treating conditions of aging, such as diabetes and heart disease. This has really opened the doors to consider all types of potential uses of this therapy.”

– Credit and Resource –

Provided by Stanford University Medical Center

Telomere extension turns back aging clock in cultured human cells

Wednesday 21 January 2015

Hubble’s High-Definition Panoramic View of the Andromeda Galaxy

The largest NASA Hubble Space Telescope image ever assembled, this sweeping bird’s-eye view of a portion of the Andromeda galaxy (M31) is the sharpest large composite image ever taken of our galactic next-door neighbor. Though the galaxy is over 2 million light-years away, the Hubble Space Telescope is powerful enough to resolve individual stars in a 61,000-light-year-long stretch of the galaxy’s pancake-shaped disk. It’s like photographing a beach and resolving individual grains of sand. And there are lots of stars in this sweeping view — over 100 million, with some of them in thousands of star clusters seen embedded in the disk.

Click image to download JPEG (702kb)

This ambitious photographic cartography of the Andromeda galaxy represents a new benchmark for precision studies of large spiral galaxies that dominate the universe’s population of over 100 billion galaxies. Never before have astronomers been able to see individual stars inside an external spiral galaxy over such a large contiguous area. Most of the stars in the universe live inside such majestic star cities, and this is the first data that reveal populations of stars in context to their home galaxy.

Hubble traces densely packed stars extending from the innermost hub of the galaxy seen at the left. Moving out from this central galactic bulge, the panorama sweeps from the galaxy’s central bulge across lanes of stars and dust to the sparser outer disk. Large groups of young blue stars indicate the locations of star clusters and star-forming regions. The stars bunch up in the blue ring-like feature toward the right side of the image. The dark silhouettes trace out complex dust structures. Underlying the entire galaxy is a smooth distribution of cooler red stars that trace Andromeda’s evolution over billions of years.

Because the galaxy is only 2.5 million light-years from Earth, it is a much bigger target in the sky than the myriad galaxies Hubble routinely photographs that are billions of light-years away. This means that the Hubble survey is assembled together into a mosaic image using 7,398 exposures taken over 411 individual pointings.

The panorama is the product of the Panchromatic Hubble Andromeda Treasury (PHAT) program. Images were obtained from viewing the galaxy in near-ultraviolet, visible, and near-infrared wavelengths, using the Advanced Camera for Surveys and the Wide Field Camera 3 aboard Hubble. This cropped view shows a 48,000-light-year-long stretch of the galaxy in its natural visible-light color, as photographed with Hubble’s Advanced Camera for Surveys in red and blue filters.

The panorama is being presented at the 225th Meeting of the Astronomical Society in Seattle, Washington.

NASA is exploring our solar system and beyond to understand the universe and our place in it. We seek to unravel the secrets of our universe, its origins and evolution, and search for life among the stars. Today’s announcement shares the discovery of our ever-changing cosmos, and brings us closer to learning whether we are alone in the universe.

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington.

For images and more information about Hubble, visit: http://www.nasa.gov/hubble or http://hubblesite.org/news/2015/02

– Credit and Resource –

NASA

Hubble’s High-Definition Panoramic View of the Andromeda Galaxy

Tuesday 20 January 2015

MIT researchers find where visual memories are made

Discovery could lead to new treatments for cognitive disorders including autism and schizophrenia.

In findings that may lead to new treatments for cognitive disorders, researchers at MIT’s Picower Institute for Learning and Memory zero in on how the brain forms memories of what has been seen.

A small region of the brain called the primary visual cortex can be targeted using a virus (light green) to block habituation learning.

In a paper appearing this week in the online edition of Nature Neuroscience, a research team led by Mark Bear, the Picower Professor of Neuroscience, showed that dramatic changes occur in the primary visual cortex when mice learn to distinguish novel from familiar visual stimuli. Manipulations that prevented the changes in visual cortex also blocked memory formation.

Impairments in detecting and recognizing familiar visual elements and patterns are features of a number of neuropsychiatric disorders, including autism and schizophrenia. With these new findings, “we now have an opportunity to investigate how gene mutations that cause or increase the risk for these disorders disrupt the mechanisms of visual recognition memory,” says Bear, a Howard Hughes Medical Institute investigator. “We anticipate that this knowledge will suggest entirely novel approaches to treating these diseases.”

To understand the physical basis of memory, researchers seek to identify where and how the brain changes as learning occurs — something that has been very difficult to achieve.

The study’s lead author, Picower Institute research scientist Samuel F. Cooke, working with postdoctoral fellows Robert W. Komorowski and Jeffrey Gavornik and graduate student Eitan S. Kaplan, showed that mice move to investigate a visual stimulus that has never before been experienced, but stop moving when the same stimulus becomes familiar. They discovered that as familiarity was learned, synaptic transmission was changed in the primary visual cortex. Preventing or reversing this synaptic plasticity in visual cortex left the animals unable to distinguish familiar and novel visual stimuli.

Previously, the primary visual cortex was seen as a “first responder” to visual stimuli that quickly passes information along to higher-order brain regions for interpretation and memory storage. “The study points to the visual cortex as a tool of learning and memory in its own right, capable of storing simple but fundamentally important memories,” Cooke says. “Our work provides great hope for the future as it suggests we may have the chance to directly observe neurons undergo lasting changes as a very simple and experimentally constrained memory is formed.”

Bear anticipates that the results will surprise neuroscientists. “We find that, contrary to the dogma that the primary visual cortex is relatively immutable in adults, a form of visual experience induces synaptic modifications in this area, and these modifications are necessary for a type of visual recognition memory.”

This work was supported by the Howard Hughes Medical Institute, the National Eye Institute, the Picower Institute Innovation Fund and the Picower Neurological Disorder Research Fund.

– Credit and Resource –

Picower Institute for Learning and Memory

MIT researchers find where visual memories are made

Particles accelerate without a push

New analysis shows a way to self-propel subatomic particles, extend the lifetime of unstable isotopes.

Some physical principles have been considered immutable since the time of Isaac Newton: Light always travels in straight lines. No physical object can change its speed unless some outside force acts on it.

This image shows the spatial distribution of charge for an accelerating wave packet, representing an electron, as calculated by this team’s approach. Brightest colors represent the highest charge levels. The self-acceleration of a particle predicted by this work is indistinguishable from acceleration that would be produced by a conventional electromagnetic field.

Not so fast, says a new generation of physicists: While the underlying physical laws haven’t changed, new ways of “tricking” those laws to permit seemingly impossible actions have begun to appear. For example, work that began in 2007 proved that under special conditions, light could be made to move along a curved trajectory — a finding that is already beginning to find some practical applications.

Now, in a new variation on the methods used to bend light, physicists at MIT and Israel’s Technion have found that subatomic particles can be induced to speed up all by themselves, almost to the speed of light, without the application of any external forces. The same underlying principle could also be used to extend the lifetime of some unstable isotopes, perhaps opening up new avenues of research in basic particle physics.

The findings, based on a theoretical analysis, were published in the journal Nature Physics by MIT postdoc Ido Kaminer and four colleagues at the Technion.

The new findings are based on a novel set of solutions for a set of basic quantum-physics principles called the Dirac equations; these describe the relativistic behavior of fundamental particles, such as electrons, in terms of a wave structure. (In quantum mechanics, waves and particles are considered to be two aspects of the same physical phenomena). By manipulating the wave structure, the team found, it should be possible to cause electrons to behave in unusual and counterintuitive ways.

Unexpected behavior

This manipulation of waves could be accomplished using specially engineered phase masks — similar to those used to create holograms, but at a much smaller scale. Once created, the particles “self-accelerate,” the researchers say, in a way that is indistinguishable from how they would behave if propelled by an electromagnetic field.

“The electron is gaining speed, getting faster and faster,” Kaminer says. “It looks impossible. You don’t expect physics to allow this to happen.”

It turns out that this self-acceleration does not actually violate any physical laws — such as the conservation of momentum — because at the same time the particle is accelerating, it is also spreading out spatially in the opposite direction.

“The electron’s wave packet is not just accelerating, it’s also expanding,” Kaminer says, “so there is some part of it that compensates. It’s referred to as the tail of the wave packet, and it will go backward, so the total momentum will be conserved. There is another part of the wave packet that is paying the price for the main part’s acceleration.”

It turns out, according to further analysis, that this self-acceleration produces effects that are associated with relativity theory: It is a variation on the dilation of time and contraction of space, effects predicted by Albert Einstein to take place when objects move close to the speed of light. An example of this is Einstein’s famous twin paradox, in which a twin who travels at high speed in a rocket ages more slowly than another twin who remains on Earth.

Extending lifetimes

In this case, the time dilation could be applied to subatomic particles that naturally decay and have very short lifetimes — causing these particles to last much longer than they ordinarily would.

This could make it easier to study such particles by causing them to stay around longer, Kaminer suggests. “Maybe you could measure effects in particle physics that you couldn’t do otherwise,” he says.

In addition, it might induce differences in the behavior of those particles that might reveal new, unexpected aspects of physics. “You could get different properties — not just for electrons, but for other particles as well,” Kaminer says.

Now that these effects have been predicted based on theoretical calculations, Kaminer says it should be possible to demonstrate the phenomenon in laboratory experiments. He is beginning work with MIT physics professor Marin Soljačić on the design of such experiments.

The experiments would make use of an electron microscope fitted with a specially designed phase mask that would produce 1,000 times higher resolution than those used for holography. “It’s the most exact way known today to affect the field of the electron,” Kaminer says.

While this is such early-stage work that it’s hard to predict what practical applications it might eventually have, Kaminer says this unusual way of accelerating electrons might prove to have practical uses, such as for medical imaging.

“Research on self-accelerating and shape-preserving beams became very active in recent years, with demonstration of different types of optical, plasmonic, and electron beams, and study of their propagation in different media,” says Ady Arie, a professor of electrical engineering at Tel Aviv University who was not involved in this research. “The authors derive shape-preserving solutions for the Dirac equation that describe the wave propagation of relativistic particles, which were not taken into account in most of the previous works.”

Arie adds, “Perhaps the most interesting result is the use of these particles to demonstrate the analog of the famous twin paradox of special relativity: The authors show that time dilation occurs between a self-accelerating particle that propagates along a curved trajectory and its ‘twin’ particle that remains at rest.”

In addition to Kaminer, who was the paper’s lead author, the research team included Jonathan Nemirovsky, Michael Rechtsman, Rivka Bekenstein, and Mordecai Segev, all of the Technion. The work was supported by the Israeli Center of Research Excellence, the U.S.-Israel Binational Science Foundation, and a Marie Curie grant from the European Commission.

– Credit and Resource –

David L. Chandler | MIT News Office

Particles accelerate without a push

Sorting cells with sound waves

Acoustic device that separates tumor cells from blood cells could help assess cancer’s spread.

Researchers from MIT, Pennsylvania State University, and Carnegie Mellon University have devised a new way to separate cells by exposing them to sound waves as they flow through a tiny channel. Their device, about the size of a dime, could be used to detect the extremely rare tumor cells that circulate in cancer patients’ blood, helping doctors predict whether a tumor is going to spread.

Illustration: Christine Daniloff/MIT

Separating cells with sound offers a gentler alternative to existing cell-sorting technologies, which require tagging the cells with chemicals or exposing them to stronger mechanical forces that may damage them.

“Acoustic pressure is very mild and much smaller in terms of forces and disturbance to the cell. This is a most gentle way to separate cells, and there’s no artificial labeling necessary,” says Ming Dao, a principal research scientist in MIT’s Department of Materials Science and Engineering and one of the senior authors of the paper, which appears this week in the Proceedings of the National Academy of Sciences.

This microfluidic device uses sound waves to sorts cells as they flow through the channel, from left to right.
Image courtesy of the researchers

Subra Suresh, president of Carnegie Mellon, the Vannevar Bush Professor of Engineering Emeritus, and a former dean of engineering at MIT, and Tony Jun Huang, a professor of engineering science and mechanics at Penn State, are also senior authors of the paper. Lead authors are MIT postdoc Xiaoyun Ding and Zhangli Peng, a former MIT postdoc who is now an assistant professor at the University of Notre Dame.

The researchers have filed for a patent on the device, the technology of which they have demonstrated can be used to separate rare circulating cancer cells from white blood cells.

To sort cells using sound waves, scientists have previously built microfluidic devices with two acoustic transducers, which produce sound waves on either side of a microchannel. When the two waves meet, they combine to form a standing wave (a wave that remains in constant position). This wave produces a pressure node, or line of low pressure, running parallel to the direction of cell flow. Cells that encounter this node are pushed to the side of the channel; the distance of cell movement depends on their size and other properties such as compressibility.

However, these existing devices are inefficient: Because there is only one pressure node, cells can be pushed aside only short distances.

The new device overcomes that obstacle by tilting the sound waves so they run across the microchannel at an angle — meaning that each cell encounters several pressure nodes as it flows through the channel. Each time it encounters a node, the pressure guides the cell a little further off center, making it easier to capture cells of different sizes by the time they reach the end of the channel.

Researchers from MIT, Penn State, and Carnegie Mellon University show how they separate cells and particles using sound waves. Video: Melanie Gonick/MIT

This simple modification dramatically boosts the efficiency of such devices, says Taher Saif, a professor of mechanical science and engineering at the University of Illinois at Urbana-Champaign. “That is just enough to make cells of different sizes and properties separate from each other without causing any damage or harm to them,” says Saif, who was not involved in this work.

In this study, the researchers first tested the system with plastic beads, finding that it could separate beads with diameters of 9.9 and 7.3 microns (thousandths of a millimeter) with about 97 percent accuracy. They also devised a computer simulation that can predict a cell’s trajectory through the channel based on its size, density, and compressibility, as well as the angle of the sound waves, allowing them to customize the device to separate different types of cells.

To test whether the device could be useful for detecting circulating tumor cells, the researchers tried to separate breast cancer cells known as MCF-7 cells from white blood cells. These two cell types differ in size (20 microns in diameter for MCF-7 and 12 microns for white blood cells), as well as density and compressibility. The device successfully recovered about 71 percent of the cancer cells; the researchers plan to test it with blood samples from cancer patients to see how well it can detect circulating tumor cells in clinical settings. Such cells are very rare: A 1-milliliter sample of blood may contain only a few tumor cells.

“If you can detect these rare circulating tumor cells, it’s a good way to study cancer biology and diagnose whether the primary cancer has moved to a new site to generate metastatic tumors,” Dao says. “This method is a step forward for detection of circulating tumor cells in the body. It has the potential to offer a safe and effective new tool for cancer researchers, clinicians and patients,” Suresh says.

The research was funded by the National Institutes of Health and the National Science Foundation.

– Credit and Resource –

Anne Trafton | MIT News Office

Sorting cells with sound waves

New way to model sickle cell behavior

Microfluidic device allows researchers to predict behavior of patients’ blood cells.

As red blood cells from sickle cell patients flow through the new MIT microfluidic device, many of them become sickled following exposure to a low-oxygen environment (left). At right, when oxygen levels are restored, the cells resume their normal shape.

Patients with sickle cell disease often suffer from painful attacks known as vaso-occlusive crises, during which their sickle-shaped blood cells get stuck in tiny capillaries, depriving tissues of needed oxygen. Blood transfusions can sometimes prevent such attacks, but there are currently no good ways to predict when a vaso-occlusive crisis, which can last for several days, is imminent.

“You don’t know exactly when it’s going to happen or how to reliably predict it is coming,” says Ming Dao, a principal research scientist in MIT’s Department of Materials Science and Engineering.

Now, Dao and colleagues, including Subra Suresh, president of Carnegie Mellon University, former dean of MIT’s School of Engineering, and Vannevar Bush Professor of Engineering Emeritus, have developed a tiny microfluidic device that can analyze the behavior of blood from sickle cell disease patients. This device can measure how long it takes blood cells to become dangerously stiff, making them more likely to get trapped in blood vessels.

Future versions of this device could be used to predict and prevent vaso-occlusive crises, says Dao, one of the senior authors of a paper describing the device in this week’s issue of the Proceedings of the National Academy of Sciences. It could also help researchers test the efficacy of new drugs for sickle cell disease, which occurs in about 300,000 newborns per year, more than 75 percent of them in Africa. The best drug now available, hydroxyurea, works for only about two-thirds of patients.

The research team also includes the paper’s lead author, E (Sarah) Du, a former MIT postdoc who is now an assistant professor at Florida Atlantic University; Monica Diez-Silva, a former research scientist in MIT’s Department of Materials Science and Engineering; and Gregory Kato of the Department of Medicine at the University of Pittsburgh.

Squeezing by

People with sickle cell disease, an inherited genetic disorder, have a variant form of hemoglobin that causes their red blood cells to take on a characteristic sickle shape when in low-oxygen conditions. Patients now have an average life expectancy of 45 to 50 years in the United States, up from only 14 years as recently as 1973.

Disease severity varies among patients depending on how much abnormal hemoglobin is present in their cells. Sickle cells can squeeze through most blood vessels, but they can encounter problems when they enter very small capillaries (less than 20 micrometers in diameter, or about one-fourth the diameter of a human hair). As blood flows through these tiny capillaries, oxygen diffuses from the blood into the surrounding tissue, supplying them with the essential gas. This blood deoxygenation causes the hemoglobin in sickle cells to form long fibrous chains, making the cells stiffer and less able to squeeze through narrow capillaries.

However, there is currently no good way to model how this deoxygenation affects patients’ red blood cells, which do not all behave the same way, making it hard to predict the risk of a vaso-occlusive crisis, Dao says.

He and his colleagues designed their microfluidic device to mimic the conditions inside a blood vessel as oxygen leaves the blood. Cells flow through a narrow channel that wraps around a compartment containing oxygen. Oxygen diffuses from the gas compartment to the microfluidic channel, allowing researchers to control how much oxygen cells are exposed to.

Learn about a microfluidic device that can predict the behavior of sickle cells, and may lead to improved treatments for those with sickle cell disease. Video: Melanie Gonick/MIT (with footage from Ming Dao)

Analyzing risk

Using this device to measure blood samples from 25 sickle cell disease patients, the researchers were able to determine how deoxygenation affects red blood cells’ sickling rates; their rate of getting stuck in capillaries; and how quickly they regain their usual shape when oxygen levels are restored. They also identified two patients whose cell sickling was much more severe than the others. They now plan to undertake more extensive studies of patient samples to demonstrate if the device can be used to reliably predict individual patients’ risk of a vaso-occlusive crisis.

“This technique represents a major advance to further our understanding and treatment of vaso-occlusion due to sickle cell disease. The microfluidic device and technique could also be potentially beneficial in studying and treating other diseases where the deformability of blood cells is affected,” says Guruswami Ravichandran, a professor of aeronautics and mechanical engineering at Caltech who was not involved in this study.

The researchers have filed a patent on the device to further its development for diagnostic use, and they also plan to pursue it as a tool to test potential new drugs for sickle cell disease.

To demonstrate the device’s usefulness for evaluating new drugs, the researchers analyzed a drug called Aes-103, now in phase II clinical trials to treat sickle cell disease, and found that it helped prevent patients’ cells from clogging in the microfluidic channel.

They also studied cells treated with hydroxyurea and found that the drug is more effective against red blood cells of higher density, which usually have more abnormal hemoglobin and are more likely to get stuck in capillaries.

The research was funded by the National Institutes of Health and Carnegie Mellon University.

– Credit and Resource –

Anne Trafton | MIT News Office

New way to model sickle cell behavior

Dawn Captures new images of Ceres

As NASA’s Dawn spacecraft closes in on Ceres, new images show the dwarf planet at 27 pixels across, about three times better than the calibration images taken in early December. These are the first in a series of images that will be taken for navigation purposes during the approach to Ceres.

Freedawn Scientia – Dawn’s arrival at Ceres will mark the first time a spacecraft has ever visited a dwarf planet. Dawn delivers new image of Ceres

Over the next several weeks, Dawn will deliver increasingly better and better images of the dwarf planet, leading up to the spacecraft’s capture into orbit around Ceres on March 6. The images will continue to improve as the spacecraft spirals closer to the surface during its 16-month study of the dwarf planet.

“We know so much about the solar system and yet so little about dwarf planet Ceres. Now, Dawn is ready to change that,” said Marc Rayman, Dawn’s chief engineer and mission director, based at NASA’s Jet Propulsion Laboratory in Pasadena, California.

The best images of Ceres so far were taken by NASA’s Hubble Space Telescope in 2003 and 2004. This most recent images from Dawn, taken January 13, 2015, at about 80 percent of Hubble resolution, are not quite as sharp. But Dawn’s images will surpass Hubble’s resolution at the next imaging opportunity, which will be at the end of January.

“Already, the [latest] images hint at first surface structures such as craters,” said Andreas Nathues, lead investigator for the framing camera team at the Max Planck Institute for Solar System Research, Gottingen, Germany.

Ceres is the largest body in the main asteroid belt, which lies between Mars and Jupiter. It has an average diameter of 590 miles (950 kilometers), and is thought to contain a large amount of ice. Some scientists think it’s possible that the surface conceals an ocean.

This is a raw image, taken Jan. 13, 2015, showing the dwarf planet Ceres as seen from the Dawn spacecraft on its approach. The spacecraft is scheduled to arrive at Ceres on March 6, 2015. Dawn’s framing camera took this image at 238,000 miles (383,000 kilometers) from Ceres. Credit: NASA

Dawn’s arrival at Ceres will mark the first time a spacecraft has ever visited a dwarf planet.

“The team is very excited to examine the surface of Ceres in never-before-seen detail,” said Chris Russell, principal investigator for the Dawn mission, based at the University of California, Los Angeles. “We look forward to the surprises this mysterious world may bring.”

The spacecraft has already delivered more than 30,000 images and many insights about Vesta, the second most massive body in the asteroid belt. Dawn orbited Vesta, which has an average diameter of 326 miles (525 kilometers), from 2011 to 2012. Thanks to its ion propulsion system, Dawn is the first spacecraft ever targeted to orbit two deep-space destinations.

This processed image, taken Jan. 13, 2015, shows the dwarf planet Ceres as seen from the Dawn spacecraft. The image hints at craters on the surface of Ceres. The spacecraft is scheduled to arrive at Ceres on March 6, 2015. Dawn’s framing camera took this image at 238,000 miles (383,000 kilometers) from Ceres.

The Dawn Framing Camera observed Ceres for an hour on January 13 from a distance of 383,000 km (near the average distance of the Moon from Earth). Ceres has a diameter of about 950 km and a rotational period of 9.1 hours, so a little more than half of its surface was observed at a resolution of 27 pixels (0.8 the resolution of Hubble observations a decade earlier). Bright and dark features can be seen in the short video constructed from the Dawn images. The bright spot to the North (up) and two larger dark spots to the South (down) were previously observed by Hubble. The dark extensions near the northern edges of the dark spots are the first new features discovered by Dawn and may represent a continuous structure extending across its mid-latitudes. As Dawn continues its approach to Ceres, it is expected that the nature of these mysterious structures will be revealed and more discoveries made. Credit: Movie courtesy of Lucille Le Corre and Vishnu Reddy, PSI. NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI

– Credit and Resource –

NASA

Dawn Captures new images of Ceres

Laser-generated surface structures create extremely water-repellent metals

Scientists at the University of Rochester have used lasers to transform metals into extremely water repellent, or super-hydrophobic, materials without the need for temporary coatings.

University of Rochester’s Institute of Optics Professor Chunlei Guo has developed a technique that uses lasers to render materials hydrophobic, illustrated in this image of a water droplet bouncing off a treated sample. Credit: J. Adam Fenster/University of Rochester

Super-hydrophobic materials are desirable for a number of applications such as rust prevention, anti-icing, or even in sanitation uses. However, as Rochester’s Chunlei Guo explains, most current hydrophobic materials rely on chemical coatings.

In a paper published today in the Journal of Applied Physics, Guo and his colleague at the University’s Institute of Optics, Anatoliy Vorobyev, describe a powerful and precise laser-patterning technique that creates an intricate pattern of micro- and nanoscale structures to give the metals their new properties. This work builds on earlier research by the team in which they used a similar laser-patterning technique that turned metals black. Guo states that using this technique they can create multifunctional surfaces that are not only super-hydrophobic but also highly-absorbent optically.

Guo adds that one of the big advantages of his team’s process is that “the structures created by our laser on the metals are intrinsically part of the material surface.” That means they won’t rub off. And it is these patterns that make the metals repel water.

“The material is so strongly water-repellent, the water actually gets bounced off. Then it lands on the surface again, gets bounced off again, and then it will just roll off from the surface,” said Guo, professor of optics at the University of Rochester. That whole process takes less than a second.

The materials Guo has created are much more slippery than Teflon—a common hydrophobic material that often coats nonstick frying pans. Unlike Guo’s laser-treated metals, the Teflon kitchen tools are not super-hydrophobic. The difference is that to make water to roll-off a Teflon coated material, you need to tilt the surface to nearly a 70-degree angle before the water begins to slide off. You can make water roll off Guo’s metals by tilting them less than five degrees.

Scientists at the University of Rochester have used lasers to transform metals into extremely water repellent, or super-hydrophobic, materials without the need for temporary coatings. Super-hydrophobic materials are desirable for a number of applications such as rust prevention, anti-icing, in solar panels or even in sanitation uses. In a paper published in the Journal of Applied Physics, Professor Chunlei Guo and his colleague at the University’s Institute of Optics, Anatoliy Vorobyev, describe a powerful and precise laser-patterning technique that creates an intricate pattern of micro- and nanoscale structures to give the metals their new properties. Credit: Matthew Mann/University of Rochester.

As the water bounces off the super-hydrophobic surfaces, it also collects dust particles and takes them along for the ride. To test this self-cleaning property, Guo and his team took ordinary dust from a vacuum cleaner and dumped it onto the treated surface. Roughly half of the dust particles were removed with just three drops of water. It took only a dozen drops to leave the surface spotless. Better yet, it remains completely dry.

Guo is excited by potential applications of super-hydrophobic materials in developing countries. It is this potential that has piqued the interest of the Bill and Melinda Gates Foundation, which has supported the work.

“In these regions, collecting rain water is vital and using super-hydrophobic materials could increase the efficiency without the need to use large funnels with high-pitched angles to prevent water from sticking to the surface,” says Guo. “A second application could be creating latrines that are cleaner and healthier to use.”

A femtosecond laser created detailed hierarchical structures in the metals, as shown in this SEM image of the platinum surface. Credit: The Guo Lab/University of Rochester

Latrines are a challenge to keep clean in places with little water. By incorporating super-hydrophobic materials, a latrine could remain clean without the need for water flushing.

But challenges still remain to be addressed before these applications can become a reality, Guo states. It currently takes an hour to pattern a 1 inch by 1 inch metal sample, and scaling up this process would be necessary before it can be deployed in developing countries. The researchers are also looking into ways of applying the technique to other, non-metal materials.

Guo and Vorobyev use extremely powerful, but ultra-short, laser pulses to change the surface of the metals. A femtosecond laser pulse lasts on the order of a quadrillionth of a second but reaches a peak power equivalent to that of the entire power grid of North America during its short burst.

Guo is keen to stress that this same technique can give rise to multifunctional metals. Metals are naturally excellent reflectors of light. That’s why they appear to have a shiny luster. Turning them black can therefore make them very efficient at absorbing light. The combination of light-absorbing properties with making metals water repellent could lead to more efficient solar absorbers – solar absorbers that don’t rust and do not need much cleaning.

Guo’s team had previously blasted materials with the lasers and turned them hydrophilic, meaning they attract water. In fact, the materials were so hydrophilic that putting them in contact with a drop of water made water run “uphill”.

Guo’s team is now planning on focusing on increasing the speed of patterning the surfaces with the laser, as well as studying how to expand this technique to other materials such as semiconductors or dielectrics, opening up the possibility of water repellent electronics.

– Credit and Resource –

More information: “Multifunctional surfaces produced by femtosecond laser pulses,” Journal of Applied Physics, January 20, 2015. DOI: 10.1063/1.4905616

Provided by University of Rochester

Laser-generated surface structures create extremely water-repellent metals

Six Methods of Imaging Nanoparticles

University at Buffalo researchers and colleagues have designed a nanoparticle detectable by six medical imaging techniques. This illustration depicts the particles as they are struck by beams of energy and emit signals that can be detected by the six methods: CT and PET scanning, along with photoacoustic, fluorescence, upconversion and Cerenkov luminescence imaging. Credit: Jonathan Lovell

Using two biocompatible parts, University at Buffalo researchers and their colleagues have designed a nanoparticle that can be detected by six medical imaging techniques:

> Computed tomography (CT) scanning;

> Positron emission tomography (PET) scanning;

> Photoacoustic imaging;

> Fluorescence imaging;

> Upconversion imaging; and

> Cerenkov luminescence imaging.

In the future, patients could receive a single injection of the nanoparticles to have all six types of imaging done.

This kind of “hypermodal” imaging—if it came to fruition—would give doctors a much clearer picture of patients’ organs and tissues than a single method alone could provide. It could help medical professionals diagnose disease and identify the boundaries of tumors.

“This nanoparticle may open the door for new ‘hypermodal’ imaging systems that allow a lot of new information to be obtained using just one contrast agent,” says researcher Jonathan Lovell, PhD, UB assistant professor of biomedical engineering. “Once such systems are developed, a patient could theoretically go in for one scan with one machine instead of multiple scans with multiple machines.”

When Lovell and colleagues used the nanoparticles to examine the lymph nodes of mice, they found that CT and PET scans provided the deepest tissue penetration, while the photoacoustic imaging showed blood vessel details that the first two techniques missed.

This transmission electron microscopy image shows the nanoparticles, which consist of a core that glows blue when struck by near-infrared light, and an outer fabric of porphyrin-phospholipids (PoP) that wraps around the core. Credit: Jonathan Lovell

Differences like these mean doctors can get a much clearer picture of what’s happening inside the body by merging the results of multiple modalities.

A machine capable of performing all six imaging techniques at once has not yet been invented, to Lovell’s knowledge, but he and his coauthors hope that discoveries like theirs will spur development of such technology.

The research, Hexamodal Imaging with Porphyrin-Phospholipid-Coated Upconversion Nanoparticles, was published online Jan. 14 in the journal Advanced Materials.

It was led by Lovell; Paras Prasad, PhD, executive director of UB’s Institute for Lasers, Photonics and Biophotonics (ILPB); and Guanying Chen, PhD, a researcher at ILPB and Harbin Institute of Technology in China. The team also included additionanl collaborators from these institutions, as well as the University of Wisconsin and POSTECH in South Korea.

The researchers designed the nanoparticles from two components: An “upconversion” core that glows blue when struck by near-infrared light, and an outer fabric of porphyrin-phospholipids (PoP) that wraps around the core.

Each part has unique characteristics that make it ideal for certain types of imaging.

The core, initially designed for upconversion imaging, is made from sodium, ytterbium, fluorine, yttrium and thulium. The ytterbium is dense in electrons—a property that facilitates detection by CT scans.

The PoP wrapper has biophotonic qualities that make it a great match for fluorescence and photoacoustic imagining. The PoP layer also is adept at attracting copper, which is used in PET and Cerenkov luminescence imaging.

“Combining these two biocompatible components into a single nanoparticle could give tomorrow’s doctors a powerful, new tool for medical imaging,” says Prasad, also a SUNY Distinguished Professor of chemistry, physics, medicine and electrical engineering at UB. “More studies would have to be done to determine whether the nanoparticle is safe to use for such purposes, but it does not contain toxic metals such as cadmium that are known to pose potential risks and found in some other nanoparticles.”

“Another advantage of this core/shell imaging contrast agent is that it could enable biomedical imaging at multiple scales, from single-molecule to cell imaging, as well as from vascular and organ imaging to whole-body bioimaging,” Chen adds. “These broad, potential capabilities are due to a plurality of optical, photoacoustic and radionuclide imaging abilities that the agent possesses.”

Lovell says the next step in the research is to explore additional uses for the technology.

For example, it might be possible to attach a targeting molecule to the PoP surface that would enable cancer cells to take up the particles, something that photoacoustic and fluorescence imaging can detect due to the properties of the smart PoP coating. This would enable doctors to better see where tumors begin and end, Lovell says.

– Credit and Resource –

More information: Advanced Materials, dx.doi.org/10.1002/adma.201404739

Provided by University at Buffalo

Six Methods of Imaging Nanoparticles