NASA, Microsoft collaboration will allow scientists to 'work on Mars'

Source : NASA/Jet Propulsion Laboratory

Summary : 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.

A screen view from OnSight, a software tool developed by NASA's Jet Propulsion Laboratory in collaboration with Microsoft. OnSight uses real rover data to create a 3-D simulation of the Martian environment where mission scientists can "meet" to discuss rover operations.

Credit: NASA/JPL-Caltech

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.

Developed by NASA's Jet Propulsion Laboratory 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.

Learn more about NASA's journey to Mars at: http://www.nasa.gov/mars

Story Source:

The above story is based on materials provided by NASA/Jet Propulsion Laboratory. Note: Materials may be edited for content and length.

Gravity weighs in on spectroscopy

The visible spectrum of neon and its characteristic emission lines. By Jan Homann via Wikimedia Commo

In 1814 the German physicist Joseph von Fraunhofer observed narrow dark lines in the otherwise continuous spectrum of light emitted by the sun. Hundreds of them. As Gustav Kirchhoff and Robert Bunsen later showed, these lines correspond to the absorption of light by various chemical elements in the sun. Each element has its own unique set of lines that correspond to energetic transition between the electronic states of these atoms. This discovery has laid the foundation to the field of spectroscopy, where the interaction of matter and light is probed.

 

A study published in Nature Physics this week by Hartmut Abele and colleagues from the University of Vienna in Austria now reports how gravity can be used instead to probe quantum states. And they’re not using atoms either, but neutrons, which are the electrically neutral particles in the atom’s core.

These neutrons are produced in nuclear research reactors, for example at the Institute Laue-Langevin (ILL) in Grenoble, which I visited last year. In fact, the experiment by Abele and colleagues was done at ILL because there ultracold neutrons are available for research – “still the only source of ultracold neutrons for users in the world,” says Peter Geltenbort from the ILL, who took part in the experiments.

These ultracold neutrons are so slow that they can be kept in a container. Even though neutrons are subatomic particles that normally can pass easily through matter, when they are sufficiently slow they don’t have enough energy to overcome nuclear forces and pass through the container walls. Instead they’re bounced back.

Here, the ultracold neutrons pass horizontally between two mirrors. The top mirror has a rough surface, which leads to the absorption of neutrons that reach the mirror. However, it is only neutron with enough energy to overcome gravity that reach the top mirror. So, at the bottom mirror neutrons are confined through the hard surface, whereas at the top they are confined by the forces of gravity. Moreover, the absorption of neutrons that reach the top mirror ensures that only neutrons with low energy can pass through the experiment.

Furthermore, the distance between the mirrors is small enough, about 20 to 25 micrometers, to distinguish between quantum states of the neutrons. These quantum states can be seen as standing waves that form between two walls. As neutrons with higher energies are absorbed by the top mirror, those neutrons remaining in the experiment are for the most part in the lowest quantum state.

Next, the researchers wiggle the lower mirror at a fixed frequency, and measure the impact this has on the neutrons after they have passed through the mirrors. They find that for certain resonance frequencies the neutrons are elevated into a higher quantum state. In other words, the experiments can be used to measure the energy difference between two quantum states of neutrons.

This experiment is therefore in direct analogy to optical spectroscopy, say on neon atoms. The quantum states of the neutrons correspond to the electronic states of neon, and the resonant movements of the bottom mirror correspond to the oscillations of the lightwave.

The implications, however, are quite different.

In spectroscopy, typically the interesting part are the electronic states of atoms and molecules. Here, such experiments could be used to learn more about gravity itself. Small deviations in the gravitational force would have a direct impact on the experiments, as these would alter the energy difference between the quantum states of the neutrons. “New forces would change or modify Newtonian gravity,” explains Abele. “Such effects are for example predicted by string theories,” adds Tobias Jenke from the team.

Furthermore, Abele says, the sensitivity of the approach beats competing techniques that use mechanical vibrations occurring in micro-scale materials. Geoffrey Greene from Oak Ridge National Laboratory and the University of Tennessee in Knoxville, United States, who works on neutron scattering experiments, agrees. “To date the best limits have been seen using very sensitive force balances, but these are limited to ranges greater than microns. Because the neutron is uncharged (and essentially non-polarizable), is massive, and is point-like down to the femtometer scale, it, in principle, could be used as a probe for very short range forces.”

Both, Greene and Abele stress that one particularly interesting force arising from string theories, and that could be verified for the first time, are so-called axion fields. In the same way that Fraunhofer’s discovery opened the door to the spectroscopy of atoms and molecules, the realization of this new spectroscopic tool could lead to an entirely new insight into gravity and related forces.

Reference:

Jenke, T., Geltenbort, P., Lemmel, H., & Abele, H. (2011). Realization of a gravity-resonance-spectroscopy technique Nature Physics DOI: 10.1038/NPHYS1970

Semiconductor optical switches reach the speed of light

Fibre optic cables transmit information so fast because they can make use of the unique properties of light and transmit many data channels at the same time. The digital 1s and 0s the light beams carry are imprinted onto the beams by semiconductors that in quick succession turn the light beam on and off. Unfortunately, that also puts a limit on the possible data rate, as materials switch slower than light. There are all-optical switches operating at the speed of light using special crystals, but what is needed are solutions that can be fabricated on a chip.

This is made possible now. Georgios Ctistis, Willem Vos, Jean-Michel Gérard and colleagues from the University of Twente and the FOM-Institute Amolf in the Netherlands, and the Institute for Nanoscience and Cryogenics in Grenoble in France have demonstrated that using a material to switch light is not a drawback anymore. They are able to switch a light beam within a semiconductor device at speeds of 0.3 picoseconds, where a picosecond is a millionth of a millionth second. That’s so fast that it approaches the limit set by the speed of light.

The principle of the ultimate optical switch. Top: a microcavity blocks the transmission of the red signal beam. Middle: in the presence of a control beam the cavity changes its properties and lets the beam pass. Bottom: as the control beam is off again, the switch also turns off. Figure provided by the authors.

In a conventional optical switch, a light beam (or an electrical voltage), is used to excite electrons in a semiconductor. These electrons then change the material’s optical properties in a way that switches the signal beam on or off. But this is a comparatively slow process. The idea here is to separate the optical effects from materials properties, which would only slow the device down. ”The key advance is that both the switch-on and -off times of the semiconductor microcavity is completely determined by the properties of light itself,” says Vos.

The way this works is to use a microcavity, where light is confined between two mirrors. The mirrors as well as the microcavity are made of precisely controlled layers of the semiconductors GaAs and AlAs, because these work particularly well for the wavelengths used in telecommunications.

The switching process involves two laser beams. It is important that these two lasers, the signal beam as well as the control beam that triggers the switching, have energies that are below the bandgap energy of the semiconductors. That way, the photons in the laser beam can’t excite electrons in the semiconductor, which as mentioned would slow down the switching. In fact, the energy of the signal beam is even less than half of the bandgap energy, so that there is not even the chance of two photons combining together to excite an electron.

Switching occurs only for that brief moment where the signal and the control beam come together. In that moment, the semiconductor microcavity, which normally would block the signal beam, lets it pass. This is due to an nonlinear optical effect, the so-called electronic Kerr effect. Again, electrons are not really relevant here, as the combined energy of signal and control beam isn’t enough to excite electrons above the bandgap. Rather, the increased light intensity, through the Kerr effect, modifies the refractive index of the semiconductors. This change in materials parameters changes the resonance frequency of the microcavity, so that light that otherwise would be trapped can escape.

Being a non-linear optical effect means that the laser intensities remain quite large says Vos. Therefore, he says, the next step now is to “switch to tiny micron-sized cavities (e.g. micropillars, photonic crystal) with weak pulses from on-chip lasers.” Smaller cavities require less switching power.

Either way, switching speeds on the order of a picosecond correspond to signal frequencies in the THz regime, which is what next generation optoelectronic switches need to achieve.  However, at this stage the researchers did not yet show successive switching at such frequencies. That’s one of their next tasks, comments Vos. “We are working hard to demonstrate repetitive switching where consecutive switch events occur every ps or so.” It won’t get much faster than that.

Reference:

Ctistis, G., Yuce, E., Hartsuiker, A., Claudon, J., Bazin, M., Gérard, J., & Vos, W. (2011). Ultimate fast optical switching of a planar microcavity in the telecom wavelength range Applied Physics Letters, 98 (16) DOI: 10.1063/1.3580615

NASA, GM Take Giant Leap in Robotic Technology

NASA and General Motors are working together to accelerate development of the next generation of robots and related technologies for use in the automotive and aerospace industries.


Engineers and scientists from NASA and GM worked together through a Space Act Agreement at the agency's Johnson Space Center in Houston to build a new humanoid robot capable of working side by side with people. Using leading edge control, sensor and vision technologies, future robots could assist astronauts during hazardous space missions and help GM build safer cars and plants.


The two organizations, with the help of engineers from Oceaneering Space Systems of Houston, developed and built the next iteration of Robonaut. Robonaut 2, or R2, is a faster, more dexterous and more technologically advanced robot. This new generation robot can use its hands to do work beyond the scope of prior humanoid machines. R2 can work safely alongside people, a necessity both on Earth and in space.


"This cutting-edge robotics technology holds great promise, not only for NASA, but also for the nation," said Doug Cooke, associate administrator for the Exploration Systems Mission Directorate at NASA Headquarters in Washington. "I'm very excited about the new opportunities for human and robotic exploration these versatile robots provide across a wide range of applications."


NASA and General Motors have come together to develop the next generation dexterous humanoid robot. The robots -- called Robonaut2 -- were designed to use the same tools as humans, which allows them to work safely side-by-side humans on Earth and in space. Credit: NASA.


"For GM, this is about safer cars and safer plants," said Alan Taub, GM's vice president for global research and development. "When it comes to future vehicles, the advancements in controls, sensors and vision technology can be used to develop advanced vehicle safety systems. The partnership's vision is to explore advanced robots working together in harmony with people, building better, higher quality vehicles in a safer, more competitive manufacturing environment."


The idea of using dexterous, human-like robots capable of using their hands to do intricate work is not new to the aerospace industry. The original Robonaut, a humanoid robot designed for space travel, was built by the software, robotics and simulation division at Johnson in a collaborative effort with the Defense Advanced Research Project Agency 10 years ago. During the past decade, NASA gained significant expertise in building robotic technologies for space applications. These capabilities will help NASA launch a bold new era of space exploration.


"Our challenge today is to build machines that can help humans work and explore in space," said Mike Coats, Johnson's center director. "Working side by side with humans, or going where the risks are too great for people, machines like Robonaut will expand our capability for construction and discovery."


NASA and GM have a long, rich history of partnering on key technologies, starting in the 1960s with the development of the navigation systems for the Apollo missions. GM also played a vital role in the development of the Lunar Rover Vehicle, the first vehicle to be used on the moon.


For more information on Robonaut and video, visit: http://robonaut.jsc.nasa.gov

Robots Created That Develop Emotions in Interaction With Humans

The first prototype robots capable of developing emotions as they interact with their human caregivers and expressing a whole range of emotions have been finalised by researchers.

Led by Dr. Lola Cañamero at the University of Hertfordshire, and in collaboration with a consortium of universities and robotic companies across Europe, these robots differ from others in the way that they form attachments, interact and express emotion through bodily expression.

Developed as part of the interdisciplinary project FEELIX GROWING (Feel, Interact, eXpress: a Global approach to development with Interdisciplinary Grounding), funded by the European Commission and coordinated by Dr. Cañamero, the robots have been developed so that they learn to interact with and respond to humans in a similar way as children learn to do it, and use the same types of expressive and behavioural cues that babies use to learn to interact socially and emotionally with others.

The robots have been created through modelling the early attachment process that human and chimpanzee infants undergo with their caregivers when they develop a preference for a primary caregiver.

They are programmed to learn to adapt to the actions and mood of their human caregivers, and to become particularly attached to an individual who interacts with the robot in a way that is particularly suited to its personality profile and learning needs. The more they interact, and are given the appropriate feedback and level of engagement from the human caregiver, the stronger the bond developed and the amount learned.

The robots are capable of expressing anger, fear, sadness, happiness, excitement and pride and will demonstrate very visible distress if the caregiver fails to provide them comfort when confronted by a stressful situation that they cannot cope with or to interact with them when they need it.

"This behaviour is modelled on what a young child does," said Dr Cañamero. "This is also very similar to the way chimpanzees and other non-human primates develop affective bonds with their caregivers."

This is the first time that early attachment models of human and non-human primates have been used to program robots that develop emotions in interaction with humans.

"We are working on non-verbal cues and the emotions are revealed through physical postures, gestures and movements of the body rather than facial or verbal expression," Dr Cañamero added.

The researchers led by Dr. Cañamero at the University of Hertfordshire are now extending the prototype further and adapting it as part of the EU project ALIZ-E, which will develop robots that learn to be carer/companion for diabetic children in hospital settings.

Within this project, coordinated by Dr Tony Belpaeme of the University of Plymouth, the Hertfordshire group will lead research related to the emotions and non-linguistic behaviour of the robots. The future robot companions will combine non-linguistic and linguistic communication to interact with the children and become increasingly adapted to their individual profiles in order to support both, therapeutic aspects of their treatment and their social and emotional wellbeing.

The FEELIX GROWING project has been funded by the Sixth Framework Programme of the European Commission. The other partners in the project are: Centre National de la Recherche Scientifique (France), Université de Cergy Pontoise (France), Ecole Polytechnique Fédérale de Lausanne (Switzerland), University of Portsmouth (U.K.), Institute of Communication and Computer Systems (Greece), Entertainment Robotics (Denmark), and Aldebaran Robotics (France).
 

Researchers Give Robots the Capability for Deceptive Behavior

 A robot deceives an enemy soldier by creating a false trail and hiding so that it will not be caught. While this sounds like a scene from one of the Terminator movies, it's actually the scenario of an experiment conducted by researchers at the Georgia Institute of Technology as part of what is believed to be the first detailed examination of robot deception.

"We have developed algorithms that allow a robot to determine whether it should deceive a human or other intelligent machine and we have designed techniques that help the robot select the best deceptive strategy to reduce its chance of being discovered," said Ronald Arkin, a Regents professor in the Georgia Tech School of Interactive Computing.

The results of robot experiments and theoretical and cognitive deception modeling were published online on September 3 in the International Journal of Social Robotics. Because the researchers explored the phenomena of robot deception from a general perspective, the study's results apply to robot-robot and human-robot interactions. This research was funded by the Office of Naval Research.

In the future, robots capable of deception may be valuable for several different areas, including military and search and rescue operations. A search and rescue robot may need to deceive in order to calm or receive cooperation from a panicking victim. Robots on the battlefield with the power of deception will be able to successfully hide and mislead the enemy to keep themselves and valuable information safe.

"Most social robots will probably rarely use deception, but it's still an important tool in the robot's interactive arsenal because robots that recognize the need for deception have advantages in terms of outcome compared to robots that do not recognize the need for deception," said the study's co-author, Alan Wagner, a research engineer at the Georgia Tech Research Institute.

For this study, the researchers focused on the actions, beliefs and communications of a robot attempting to hide from another robot to develop programs that successfully produced deceptive behavior. Their first step was to teach the deceiving robot how to recognize a situation that warranted the use of deception. Wagner and Arkin used interdependence theory and game theory to develop algorithms that tested the value of deception in a specific situation. A situation had to satisfy two key conditions to warrant deception -- there must be conflict between the deceiving robot and the seeker, and the deceiver must benefit from the deception.

Once a situation was deemed to warrant deception, the robot carried out a deceptive act by providing a false communication to benefit itself. The technique developed by the Georgia Tech researchers based a robot's deceptive action selection on its understanding of the individual robot it was attempting to deceive.

To test their algorithms, the researchers ran 20 hide-and-seek experiments with two autonomous robots. Colored markers were lined up along three potential pathways to locations where the robot could hide. The hider robot randomly selected a hiding location from the three location choices and moved toward that location, knocking down colored markers along the way. Once it reached a point past the markers, the robot changed course and hid in one of the other two locations. The presence or absence of standing markers indicated the hider's location to the seeker robot.

"The hider's set of false communications was defined by selecting a pattern of knocked over markers that indicated a false hiding position in an attempt to say, for example, that it was going to the right and then actually go to the left," explained Wagner.

The hider robots were able to deceive the seeker robots in 75 percent of the trials, with the failed experiments resulting from the hiding robot's inability to knock over the correct markers to produce the desired deceptive communication.

"The experimental results weren't perfect, but they demonstrated the learning and use of deception signals by real robots in a noisy environment," said Wagner. "The results were also a preliminary indication that the techniques and algorithms described in the paper could be used to successfully produce deceptive behavior in a robot."

While there may be advantages to creating robots with the capacity for deception, there are also ethical implications that need to be considered to ensure that these creations are consistent with the overall expectations and well-being of society, according to the researchers.

"We have been concerned from the very beginning with the ethical implications related to the creation of robots capable of deception and we understand that there are beneficial and deleterious aspects," explained Arkin. "We strongly encourage discussion about the appropriateness of deceptive robots to determine what, if any, regulations or guidelines should constrain the development of these systems." 

Electronic Pills – Collecting Data Inside The Body

After years in development, wireless devices contained in swallowable capsules are now reaching the market.

Companies such as SmartPill based in Buffalo, New York and Israel-based Given Imaging (PillCam) market capsules the size of vitamin tablets that contain sensors or tiny cameras that collect information as they travel through the gastrointestinal tract before being excreted from the body a day or two later.

These new electronic inventions transmit information such as acidity, pressure and temperature levels or images of the esophagus and intestine to your doctor’s computer for analysis.

Doctors often use invasive methods such as catheters, endoscopic instruments or radioisotopes for collecting information about the digestive tract. So device companies have been developing easier, less intrusive ways, to gather information.

Digestive diseases and disorders can include symptoms such as acid reflux, bloating, heartburn, abdominal pain, constipation, difficulty swallowing or loss of appetite.

“One of the main challenges is determining just what is happening in the stomach and intestines.” says Dr. Anish A. Sheth, Director of the Gastrointestinal Motility Program at Yale-New Haven Hospital.

Doctors can inspect the colon and peer into the stomach using endoscopic instruments. But some areas cannot be easily viewed, and finding out how muscles are working can be difficult.

Electronic pills are being used to measure muscle contraction, ease of passage and other factors to reveal information unavailable in the past.

Maple trees can be used to produce electricity to power small gadgets

Recently it was unveiled that maple trees can be used to produce electricity to power small gadgets. A report published in the journal IEEE Transactions on Nanotechnology says that maple trees produce a rather small but still measurable quantity of electricity.

Those of you who have heard about potato batteryprobably are aware that the plant material can produce current. However, the electricity produced but a tree is something completely different.

When creating a potato battery, there is a need of electrodes of two different metals in order to create a charge difference, which would make local electrodes flow. In the new study, scientists used electrodes created of the same material, reports Karen Hopkin for Scientific American. When researchers stuck one electrode into a tree while the other one was stuck into the soil, they noticed that big leaf maples produced a steady voltage of a few hundred millivolts.

In case scientists will continue exploring their finding, in the near future people could use maple trees to power various devices. This is due to the fact that scientist from the University of Washington in Seattle discovered that there’s quite enough electricity flowing in maple trees in order to run an electronic circuit. More inventions and discoveries are available here at www.InfoNIAC.com – please check the links at the bottom of the story.

Because several hundred millivolts is much less than a volt and a half, generated by a AA battery, researchers decided to design a 130-nanometer device that runs just on tree power.

Latest Invention: Solar Cells Thinner Than Human Hair

The new apparatus of Sanyo, the aggregation that not so continued ago appear about its ambition to become one of the better solar manufacturers in the acreage of the ascent sun by 2010, is a solar cell, which, according to the company, is thinner than a animal hair.

The array of Sanyo’s new apparatus is aloof 58 micrometers. The new solar corpuscle was developed to ability a about-face ability of 22.8 percent.

The solar beef are fabricated of two types of silicon, their adaptability akin is agnate to that of a cardboard and its amount will be 25 percent lower than the solar beef acclimated today.

Although the new solar beef are acceptable to hit the bazaar in a decade or so, their low amount and flexibility, could advice improve the solar industry.

100 years of superconductivity

Today marks the 100th anniversary of superconductivity by Heike Kamerlingh Onnes. In a superconductor, the electrons flow without any electrical resistance.

(Heike Kamerlingh Onnes (photo from Museum Boerhaave))

Apart from their fundamental scientific interest, superconductors are used to make powerful electromagnets, for example for MRI and NMR machines in medical diagnostics. Other promising applications include power transmission cables with low losses, highly sensitive devices to measure magnetic fields and so on.

Working in his lab at Leiden University, on 8 April 1911 he experimented with the electrical resistance of mercury at low temperatures. In his notebook he noted that at 3 K (-270°C), ‘Kwik nagenoeg nul’, mercury’s resistance drops to ‘practically zero’.

 

This discovery at such low temperatures was only made possible by Kamerlingh Onnes previous achievement of liquifying helium at 4.22 K. this provided the means to cool samples down to even lower temperatures. For this breakthrough in cryogenics, Kamerlingh Onnes received the 1913 Nobel prize in physics.

When superconductivity was discovered, it certainly was a puzzling observation at the time. Some scientists believed that at low temperatures electrical resistance would shoot up towards infinity, whereas others thought that it would gradually go down, which is what indeed happens for many materials. However, superconductivity is not simply a new form of electrical resistance – it is a thermodynamic state in its own right, and its unique properties can’t be explained by classical physics alone. Indeed, it was not until 1957, when Bardeen, Cooper and Schrieffer provided the quantum-theory that explains superconductivity of materials such as mercury.

However, that’s not where research into superconductivity stops. In 1987, the so-called high-temperature superconductors were discovered. Their superconducting temperatures are so high that cooling with helium isn’t even necessary. Interestingly, mercury (Hg) plays a key role there as well: the superconductor with the highest known temperature at normal pressures (135 K) is HgBa₂Ca₂Cu₃O_x!

The origin of superconductivity in these new superconductors is different to the classical superconductors, and remains not fully understood. This makes Kamerlingh Onnes discovery all the more relevant to this day.

Further reading:

it seems this nice article is free access:

van Delft, D., & Kes, P. (2010). The discovery of superconductivity Physics Today, 63 (9) DOI: 10.1063/1.3490499

The ultimate x-ray machines are ready to go

X-ray data of protein crystals obtained from over 15,000 single snapshots. Credit: Thomas White, DES

When you go to the doctor for an X-ray, the nurse or doctor briefly disappear behind a screen, presses a button for a brief moment, and you’re all set. It seems an X-ray takes about a second but the actual exposure times is much faster. Milliseconds more likely.

Such speeds seem like almost an eternity compared to what is achieved by a new generation of X-ray sources that have begun to become operational: free-electron X-ray lasers. The first of these big machines is the LCLS at Stanford University, which achieves laser pulses shorter than 70 femtoseconds (100 femtoseconds = 1/10 of a trillionth of a second). The beam intensities of these lasers are ten billion times brighter than the sun. And all this with a potential imaging precision down to the atomic scale. In other words, if you like to take things to the extreme, these lasers are for you.

In one of the first studies to make use of the LCLS X-ray free-electron laser, two research collaborations now present first experiments on biological samples in this week’s Nature.

Imaging biological samples

Bones appear much stronger in X-ray scans than soft tissue. That’s because X-rays don’t interact so much with the carbon and hydrogen atoms of soft organic tissue, which makes it more difficult to measure with X-rays. And that’s why these two Nature studies are so relevant. The first of these studies looked at a mimivirus, which with a size of 0.45 micrometers is the largest virus known. The aim was to take a picture of the virus’ interior by measuring the diffraction of the X-rays by the virus.

To image such a small object in this way the X-ray beam is highly focused, to a spot of about 10 micrometers in size. At the same time laser beam intensities are immense: the researchers calculate that a single laser pulse heats the sample by 100,000 K. But that doesn’t really matter. Only one pulse passes through the sample and that is so short that the heating begins only after the X-rays have passed through. The viruses never know what hit them. The image of the virus taken with such a single shot has a resolution of about 32 nanometers, and does indeed show a somewhat softer virus interior.

The topic of the second paper also uses the diffraction of X-rays, but to measure the structure of a protein. To achieve optimum resolution, more than three million snapshots were taken. Of course, because of the high beam intensities the protein can’t stay in the laser beam all this time. Rather, the crystals are flushed through the apparatus in a water jet. The resolution the researchers achieve this way is about 8.5 Angstrom, which is actually not better than what the competition, synchrotrons, can achieve. The benefit of these free electron lasers is, however, that the pulses are so short that the samples don’t need to be cooled down. Room temperature is perfectly fine.

What are these free-electron lasers?

In an X-ray free electron laser the electrons are first accelerated to extreme velocities close to the speed of light. Then these fast electrons are sent on a narrow rollercoaster ride through the so-called undulator. This tight wiggling motion causes a strong emission of short light pulses. And given the high energy that these electrons have this means X-rays.

The benefit of these X-ray lasers is that you can get an extremely high imaging resolution combined with these very short exposure times, along with extremely high intensities. That for the first time opens the door to X-ray studies of dynamic processes at resolutions down to the atomic scale. In biological samples, this might be useful to understand molecular processes. In physics, one could study how atoms in a crystal move, for example in response to electric fields.

Given such clear benefits, it is no surprise that there are several X-ray free-electron lasers that either just started operating or are about to become operational. The first one for high-energy X-rays was LCLS, which at the moment enjoys the benefit of being the first off the marks. XFEL in Hamburg, Germany and XFEL at SPring-8 near Himejiin Japan are the next ones to follow. Last year I had the privilege to visit the XFEL in Japan when it was under construction. This gave me the opportunity to look inside the machine at sections that are usually off-limits. Below are some of the photos taken by other. 

 

The long accelerator line. electrons are accelerated over a distance of more than 400 meters. Once accelerated the electrons are fed into the undulators.	The undulators are being installed. The narrow stripe inside the tube, flanked by magnets, is where the electrons are sent on their wiggling path. During operation this tube is under vacuum.
The detector apparatus that will hold the custom-made CCD chips. Note the copper cooling tubes.	One of the expensive CCD test chips. It has 512x1024 pixels. Each pixel is 50 micrometers wide - quite large, so that only 3000 photons are needed to generate a signal.

 References:

1. Seibert, M. et al. (2011). Single mimivirus particles intercepted and imaged with an X-ray laser Nature, 470 (7332), 78-81 DOI: 10.1038/nature09748

2. Chapman, H. et al. (2011). Femtosecond X-ray protein nanocrystallography Nature, 470 (7332), 73-77 DOI: 10.1038/nature09750

How to make a transistor based on electron spin (Quantum mechanics)

In spin electronics, it is the spin of the electron and not its electrical charge that could be used for computing. Indeed, this could be done entirely without electrical currents, and would be more energy efficient as it is easier to switch a spin than carry an electric current. In such devices, the spin can assume two orientations, which can be used to represent the 1 and 0 of computer bits.

The fundamental unit of a computer is the transistor. So what about the equivalent for spin electronics, the spin transistor? Well, the concept of a transistor that only switches an electron’s spin instead of charge was proposed 20 years ago by Supriyo Datta and Biswajit Das, but was never realized. The problem has been to control the spin of an electron in a clear and efficient way by electrical voltages while it is in transit through a nanoscale device.

( The Spin Hall effect transistor. (c) Science 330, 1801 (2010) )

Work by Jörg Wunderlich from the Hitachi Laboratory in Cambridge, Tomas Jungwirth from the Institute of Physics in Prague and the University of Nottingham in the UK, and their colleagues now published in Science comes the closest yet to the Datta-Das spin transistor: they present a spin Hall effect transistor.

Unlike the Datta-Das transistor, which basically is the concept of the conventional transistor transferred to spin electronics, the spin Hall effect transistor is a little more elaborate. The researchers excite electrons with a predefined spin (yellow cylinder in the figure). As the electrons travel from there to the other end of the device they scatter and get diverted either to the left or the right, depending on the direction their spin is pointing at. If the electrons all have spins pointing in the same direction, as in the experiment, they all get deflected in the same direction. This creates a Hall voltage along a crossbar (R_H in the figure), even though no electric current flows in this device.

Another crossbar close to the point where the electrons with uniform spin are excited ensures no electrical currents can flow, because this crossbar is electrically grounded and therefore sets any voltages to zero. The spin orientation, however survives. Otherwise there would be no Hall voltage in the experiments.

So far, there is nothing too surprising, the spin Hall effect is known. What is new in this structure is that a transistor element is added: the gate. In a conventional transistor the gate voltage (V_G) controls the flow of electrons and turns the transistor on and off, which means it can switch the bits from 1 to 0. The researchers now apply a similar voltage to their structure. And even though no electric current flows, this voltage turns the transport of spin, and hence the Hall voltage, on and off.

Even though this structure is a good deal more complicated than a conventional transistor, it demonstrates the principle that a pure spin current can be controlled in a similar way to a conventional transistor. Of course, we are still far away from applications. For example, the spin signal is created optically and not electronically. But what it accomplishes beautifully is to show how close we have come to realize a spin transistor. Twenty years after the paper of Datta and Das it is about time!

References:

Datta, S., & Das, B. (1990). Electronic analog of the electro-optic modulator Applied Physics Letters, 56 (7) DOI: 10.1063/1.102730

Wunderlich, J., Park, B., Irvine, A., Zarbo, L., Rozkotova, E., Nemec, P., Novak, V., Sinova, J., & Jungwirth, T. (2010). Spin Hall Effect Transistor Science, 330 (6012), 1801-1804 DOI: 10.1126/science.1195816

Get those computers spinning (Quantum physics)

( Photo by Philippe Teuwen via wikimedia. )

 

This Article discuss about new ways of computing using the quantum mechanical property of spin. Taken together, these provide a brief glimpse into the different ways researchers have progressed in incorporating spin into electronic devices.

The fundamental element of a computer chip is the transistor. The transistor is where the bits are switched from 0 to 1 and vice versa. Transistors are made from semiconductors such as silicon and operate by moving electrical charges between two contacts. But electrical charges are not the only possibility to operate a computer. Another one is to use spin.

What is spin and why do we care?

Spin is a quantity that is related to the rotation of fundamental particles around their own axis, similar to a spinning top. The concept of spin is deeply rooted in quantum mechanics, pioneered by people such as Wolgang Pauli and Niels Bohr. Of course, the analogy of such a fundamental property to a spinning top does not work fully. If you want to learn more about the intriguing world of spin, take a look at Dave Goldberg’s blog post.

But how does spin have any relevance in computing? Well, if the particle with spin also has an electrical charge, as the electron does, this also creates a magnetic field, similar to that of a tiny compass. This magnetic field can be used to store information just like an electric charge. Whether the compass points upwards or downwards then corresponds to the 0 and 1 of a bit.

What are the benefits of using spin? Open a computer and just look at the efforts that are needed to cool the computer processor so that it doesn’t overheat. In conventional electronics there is a lot of energy loss and heat generation. Spin can be switched with much less energy. Furthermore, spin is a property of all materials, not just semiconductors. And last but certainly not least, unlike the memory of a transistor, the information stored in spin is not necessarily lost if a computer is turned off. This could be useful for computers that don’t need to be booted after being turned off.

( Wolfgang Pauli and Niels Bohr look at a spinning top. Bohr and Pauli are pioneers of quantum mechanics, where the concept of spin is rooted. Photograph by Erik Gustafson, courtesy AIP Emilio Segre Visual Archives, Margrethe Bohr Collection )

Spins aligned

To use spin for computing, one first needs to have electrons whose spins all point in the same direction. There are a number of ways to achieve this. Magnetic fields are an obvious one, as they act on spins in the same way as the Earth’s magnetic field on compass needles.

The approach that Marius Costache and Sergio Valenzuela from the Universitat Autònoma de Barcelona in Spain have now chosen has the added benefit that it also transports the spin across a device — without actually transporting any electrons.

In their work, the first spin-related paper in this week’s Science, they fabricate a small superconducting ‘island’ that is connected from both sides with electrical wires. The island is so small that if an excess electron is brought on the island its electrical charge is sufficient to deter other electrons from travelling across the island. Also, the energy of that single electron is above the energy of the ‘sea’ of superconducting electrons.

The researchers now apply an external magnetic field in upward direction. This lowers the energy of electrons with spin aligned in the same direction and increases the energy barrier for those in downwards direction. This makes a perfect spin filter that is selective for electrons with the right spin orientations. But because of the superconducting properties of the island, no real electrons are passing through, only the spin orientation is transferred from one side to the other. The drawback is of course that this only works at the low temperatures at which superconductors operate.

Manipulating spin

The second paper in Science deals with another issue: how to manipulate the spin in a thin magnetic layer? Christian Pfleiderer from the Technical University of Munich and colleagues use a known approach to turn this spin around, which is an electrical current made of electrons that have spin in the direction the switching will take place. This ‘spin-torque effect’ is something like a brute-force approach as the sheer mass of electrons of spin in the other direction eventually changes the spin of the magnetic layer. It is as if you walk against a large crowd of people that eventually force you to walk in their direction. Because of the large electron current required, this torque effect has been only possible in nanostructures, where heating effects won’t be a problem. Pfleiderer and colleagues have now discovered that the spin-torque works very well in the magnet MnSi, where the spins form a complex assemblies, so-called skyrmions. These skyrmions reverse their direction much easier than conventional magnets, so that the electrical currents required are orders of magnitude smaller. The drawback here is that this still is a quite elaborate experimental far away from the device stage.

Storing spin

Magnets are of course ideal to store spin information for a long time. But there magnetism is set by the atoms and not by free electrons. To combine spin and electronics, however, it would be desirable to find ways to store spin with electrons. This is possible with the spins in the atomic nucleus, as these can be addressed by electrons and nuclear spins have comparatively long lifetimes. Christoph Boehme from the University of Utah and colleagues have now stored spin information in the atomic nucleus of phosphorus atoms embedded in a silicon chip. They demonstrate that the lifetimes of these spins are larger than 100 seconds. The benefit is that this is done completely electronically, and it is in silicon, which is the best material to combine spin electronics and regular electronics. On the other hand, this approach may not yet have reached the easy of implementation and reliability required for applications.

Of course, these three papers only provide a very specific view into some areas explored for spin electronics. And while the concept of electronics being to a large extend driven by spin instead of electrical charges is very appealing, it is still a long way for most of these approaches to become technologically viable. Nevertheless, the variety of ideas and approaches currently pursued is impressive and a good indicator of the ingenuity of researchers and the interesting physics coming out of this field as it moves closer towards applications.

References:

Costache, M., & Valenzuela, S. (2010). Experimental Spin Ratchet Science, 330 (6011), 1645-1648 DOI: 10.1126/science.1196228

Jonietz, F., Muhlbauer, S., Pfleiderer, C., Neubauer, A., Munzer, W., Bauer, A., Adams, T., Georgii, R., Boni, P., Duine, R., Everschor, K., Garst, M., & Rosch, A. (2010). Spin Transfer Torques in MnSi at Ultralow Current Densities Science, 330 (6011), 1648-1651 DOI: 10.1126/science.1195709

McCamey, D., Van Tol, J., Morley, G., & Boehme, C. (2010). Electronic Spin Storage in an Electrically Readable Nuclear Spin Memory with a Lifetime 100 Seconds Science, 330 (6011), 1652-1656 DOI: 10.1126/science.1197931

Light does matter (Quantum physics)

Light is special. In our everyday experience it behaves like a wave, which gets reflected, refracted and shows interference with other light of the same wavelength. At the same time, light also consists of particles, so-called photons. This duality is quite fundamental: the Hanbury Brown and Twiss experiment for example only works because of the particle-like properties of light.

This amazing and perhaps confusing duality, where light in one experiment appears to be a wave and in others it behaves like particles, is now laid bare in a paper published in Nature. There, Jan Klaers, Martin Weitz and colleagues from the University of Bonn in Germany take one of the classical properties of light waves and turn it upside down — by demonstrating a related effect that only works when considering the particle qualities of light!

( The experimental setup. A laser beam injects photons into a cavity filled with light, and a camera observes the photons coming out of the cavity. Reprinted by permission from Macmillan Publishers Ltd. Nature 468, 545-548 (2010).)

The classical effect they use is that light waves can all oscillate synchronously. This is exactly what happens in a laser, and is typical behaviour for a class of particles to which photons belong to, the bosons. Bosons love to be all in the same state.

A similar synchronous behaviour can also occur for other bosons, including certain atoms, which then all assume the same quantum state. This state is called a Bose-Einstein condensate, after Satyendra Nath BoseAlbert Einstein, who described it first in 1924. It is a Bose-Einstein condensate of light that Weitz and colleagues have now demonstrated. (after whom bosons are named) and

( Bose-Einstein condensation of light, as observed by a camera looking at the photons from the cavity. The narrowing of the spatial distribution as the light intensity is increased (bottom image) is a tell-tale sign. Reprinted by permission from Macmillan Publishers Ltd. Nature 468, 545-548 (2010). )

 Well, so if photons are bosons anyway, what is the big deal, what is the difference? I have to confess this was my first thought when only reading the title of the paper. A Bose-Einstein condensate of light? Simply turn on any laser, and there you have something similar. But there is a subtle difference: in the Bose-Einstein condensate of atoms, the number of atoms is conserved — atoms may drift in and out of the experimental system, but they obviously are not artificially created on the spot. This is different to a laser, where new light is created all the time.

But how to get light behave like that, like discrete atomic particles? The trick is to confine the light between two mirrors that are very close together (Fig. 1). Light only fits between the mirrors if its wavelength is short enough. But a maximum wavelength of light also means that the light has a certain minimum energy (the energy of light is inverse to its wavelength).

The minimum energy of light between the mirrors is high enough to rule out the creation of new photons, because the thermal energy from the heat is too small, and other energy sources aren’t available either. No new photons are created, and the system behaves more like a bunch of particles. Even so, at this stage we still haven’t achieved a Bose-Einstein condensate, all we have is light bouncing back and forth between two mirrors.

As in the case of atoms, the photons need to be cooled down. The purpose is to bring them closer together in energy, and this can done by a cooled dye solution that is placed between the mirrors. The interaction of the photons with the dye molecules brings them in tune with the temperature of the solution, which again is very much like what would happen for regular particles.

As a last step, to get the Bose-Einstein condensate going we need a sufficient number of particles. The images taken of light passing through the cavity show this impressively (Fig. 2). Broadly speaking, at low light intensities there aren’t enough photons to synchronise with each other to form a condensate. As a result, the light is broadly distributed. At high enough intensities, however, the Bose-Einstein condensate is clearly evident through the narrow distribution of light in a single beam. This is to some degree comparable to the narrow beam coming out of a laser, and shows the relationship between both effects.

Indeed, in many ways the properties of light in a laser and in this Bose-Einstein condensate are similar. But the similarity arises not from the wave-like property itself, but from the dual nature of light that can act as a wave as well as a particle. In that respect the demonstration of Bose-Einstein condensation of light makes a full circle: light that behaves like matter that behaves like light. Simply beautiful.

Reference:

Klaers, J., Schmitt, J., Vewinger, F., & Weitz, M. (2010). Bose–Einstein condensation of photons in an optical microcavity Nature, 468 (7323), 545-548 DOI: 10.1038/nature09567