A Deep Look Into A Single Molecule

Credit: PTB

The quantum state of a molecular ion has been measured live and in a non-destructive fashion for the first time. The interaction of thermal energy from the environment with motional degrees of freedom is well known and often referred to as Brownian motion (also thermal motion). But in the case of polar molecules, the internal degrees of freedom - in particular the rotational quantum state - are also influenced by the thermal radiation. So far, the detection of the rotational state was only possible by destroying the molecule. However, a German research group has now demonstrated the first implementation of a non-destructive state detection technique for molecular ions. Piet Schmidt and his colleagues from the QUEST-Institute at the Physikalisch-Technische Bundesanstalt (PTB) observed changes in the rotational state of a trapped and indirectly cooled molecular ion in real time and in situ. This technique enables novel spectroscopy methods with applications ranging from chemistry to tests of fundamental physics. The results are published in the current issue of "Nature". Basic concept of the experiment: MgH+ (orange) and Mg+ (green) are trapped together in a linear ion trap. The two-ion compound is cooled to the motional ground state via the atomic ion. An oscillating dipole force changes the motional state according to the rotational state of the molecular ion. This motional excitation can be detected on the atomic ion.  Nowadays atoms can be manipulated with lasers and their spectral features can be investigated with high precision e.g. in optical clocks. In these experiments state detection plays a crucial role: the fluorescence of an atom under illumination with laser light reveals its internal quantum state. Many atoms and most molecules, however, do not fluoresce at all. Therefore, one of the standard procedures for state detection in molecules exploited the fact that molecules can be broken apart with laser light of a certain frequency, depending on their quantum state. This lets one measure the quantum state of the molecule by destroying it. Of course this detection procedure can only be applied once per molecule. Project leader Piet Schmidt has a long experience of systems in which state detection is difficult to achieve. He was involved in the development of 'quantum logic spectroscopy' in the research group of Nobel laureate David J. Wineland and extended it with his own research team to 'photon recoil spectroscopy'. Typical detection signal, where a quantum jump into the (J=1)-rotational state (from red to blue area) and a subsequent jump out of this state (blue to red) can be seen All of these novel

Credit: PTB

spectroscopy techniques are based on a common principle: beside the ion under investigation, one traps a second ion of a different species that is controllable and whose fluorescence can be used for state detection. Because of their electrical repulsion, both particles behave as if they were connected by a strong spring, such that their motion is synchronized. This is how the measurement of one particle can reveal properties of the other particle. Schmidt and his colleagues use a molecular MgH+-ion (which is the subject of the investigation) and an atomic Mg+-ion (on which the measurements will be performed). They hold both particles with electric fields in an ion trap. Then, lasers are used to cool the particles' motion to the ground state, where the synchronous motion almost comes to rest. The new trick demonstrated in this experiment relies on an additional laser, whose action is similar to an optical tweezer. It can be used to exert forces on the molecule. "The laser shakes the molecule only if the molecule is in one particular rotational state" explains Fabian Wolf, physicist in Schmidt's research group "We can detect the effect¬ -which is an excitation of the common motion of the molecule and the atom- on the atomic ion by using additional lasers. If the atom lights up, the molecule was in the state we probed. If it stays dark, the molecule was in some other state." Piet Schmidt highlights two main results of the team's findings: "Because of the non-destructive nature of our technique, we could observe the molecule jumping from one rotational state to the other. It is the first time such quantum jumps have been observed directly in an isolated molecule. Moreover, we could improve on the uncertainty of a transition frequency to an electronically excited state". He also points towards future goals: "The next step is the systematic preparation of the molecule in that quantum state instead of waiting for the thermal radiation to randomly prepare it." The researchers feel confident that their development will be important for the scientific communities that need precise methods for spectroscopy, e.g. quantum chemistry, where the inner structure of molecules is investigated, or astronomy, where spectra of cold molecules can teach us new things about the origin and the properties of the universe. Furthermore, precision molecular spectroscopy is important for the search for a variation of the fundamental constants and so far hidden properties of fundamental particles, such as the electric dipole moment of the electron. These tests of fundamental physics were Schmidt's original motivation for working on the novel detection technique."To make these applications practical, we have to push molecular spectroscopy to a level similar to that of today's optical clocks based on atoms", says Piet Schmidt, when he gets asked for his long term goal, "For this purpose we have to improve our measurement resolution by orders of magnitude, which for sure will take several years". Source: http://www.ineffableisland.com/

• Contacts and sources: Prof. Dr. Piet O. Schmidt
• QUEST-Institute at the Physikalisch-Technische Bundesanstalt (PTB)
• Citation: F. Wolf, Y. Wan, J.C. Heip, F. Gebert, C. Shi, P.O. Schmidt: Non-destructive state detection for quantum logic spectroscopy of molecular ions. Nature (2016), DOI: 10.1038/nature16513

Read More........→February 15, 2016

Can Artificial Trees Generate Renewable Power

Credit: Tech Briefs

New tools for harvesting wind energy may soon look less like giant windmills and more like tiny leafless trees. A project at The Ohio State University is testing whether high-tech objects that look a bit like artificial trees can generate renewable power when they are shaken by the wind--or by the sway of a tall building, traffic on a bridge or even seismic activity. In a recent issue of the Journal of Sound and Vibration, researchers report that they've uncovered something new about the vibrations that pass through tree-shaped objects when they are shaken. Specifically, they've demonstrated that tree-like structures made with electromechanical materials can convert random forces--such as winds or footfalls on a bridge--into strong structural vibrations that are ideal for generating electricity. The idea may conjure images of fields full of mechanical trees swaying in the breeze. But the technology may prove most valuable when applied on a small scale, in situations where other renewable energy sources such as solar are not an option, said project leader Ryan Harne, assistant professor of mechanical and aerospace engineering at Ohio State, and director of the Laboratory of Sound and Vibration Research. The "trees" themselves would be very simple structures: think of a trunk with a few branches--no leaves required. Early applications would include powering the sensors that monitor the structural integrity and health of civil infrastructure, such as buildings and bridges. Harne envisions tiny trees feeding voltages to a sensor on the underside of a bridge, or on a girder deep inside a high-rise building. The project takes advantage of the plentiful vibrational energy that surrounds us every day, he said. Some sources are wind-induced structural motions, seismic activity and human activity. "Buildings sway ever so slightly in the wind, bridges oscillate when we drive on them and car suspensions absorb bumps in the road," he said. "In fact, there's a massive amount of kinetic energy associated with those motions that is otherwise lost. We want to recover and recycle some of that energy." Sensors monitor the soundness of a structure by detecting the vibrations that pass through it, he explained. The initial aim of the project is to turn those vibrations into electricity, so that structural monitoring systems could actually be powered by the same vibrations they are monitoring. Today, the only way to power most structural sensors is to use batteries or plug the sensors directly into power lines, both of which are expensive and hard to manage for sensors planted in remote locations. If sensors could capture vibrational energy, they could acquire and wirelessly transmit their data is a truly self-sufficient way. At first, the idea of using tree-like devices to capture wind or vibration energies may seem straightforward, because real trees obviously dissipate energy when they sway. And other research groups have tested the effectiveness of similar tree structures using idealized--that is, not random--vibrations. But until now, researchers haven't made a concerted effort to capture realistic ambient vibrations with a tree-shaped electromechanical device--mainly because it was assumed that random forces of nature wouldn't be very suitable for generating the consistent oscillations that yield useful electrical energies. First, through mathematical modeling, Harne determined that it is possible for tree-like structures to maintain vibrations at a consistent frequency despite large, random inputs, so that the energy can be effectively captured and stored via power circuitry. The phenomenon is called internal resonance, and it's how certain mechanical systems dissipate internal energies. In particular, he determined that he could exploit internal resonance to coax an electromechanical tree to vibrate with large amplitudes at a consistent low frequency, even when the tree was experiencing only high frequency forces. It even worked when these forces were significantly overwhelmed by extra random noise, as natural ambient vibrations would be in many environments. He and his colleagues tested the mathematical model in an experiment, where they built a tree-like device out of two small steel beams--one a tree "trunk" and the other a "branch"--connected by a strip of an electromechanical material, polyvinylidene fluoride (PVDF), to convert the structural oscillations into electrical energy. They installed the model tree on a device that shook it back and forth at high frequencies. At first, to the eye, the tree didn't seem to move because the device oscillated with only small amplitudes at a high frequency. Regardless, the PVDF produced a small voltage from the motion: about 0.8 volts. Then they added noise to the system, as if the tree were being randomly nudged slightly more one way or the other. That's when the tree began displaying what Harne called "saturation phenomena": It reached a tipping point where the high frequency energy was suddenly channeled into a low frequency oscillation. At this point, the tree swayed noticeably back and forth, with the trunk and branch vibrating in sync. This low frequency motion produced more than double the voltage--around 2 volts. Those are low voltages, but the experiment was a proof-of-concept: Random energies can produce vibrations that are useful for generating electricity. "In addition, we introduced massive amounts of noise, and found that the saturation phenomenon is very robust, and the voltage output reliable. That wasn't known before," Harne said. Harne will continue this work, which he began when he was a postdoctoral researcher at the University of Michigan. There, his colleagues and co-authors on the paper were Kon-Well Wang and Anqi Sun of the Department of Mechanical Engineering. Source: http://www.ineffableisland.com/

• Contacts and sources: Ryan Harne, The Ohio State University, 
• Written by Pam Frost Gorder 
• The initial phase of this research was supported by the University of Michigan Summer Undergraduate Research in Engineering program and the University of Michigan Collegiate Professorship. 

Read More........→February 05, 2016

Processing of Used Nuclear Fuel

Chemistry of Purex
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• Used nuclear fuel has long been reprocessed to extract fissile materials for recycling and to reduce the volume of high-level wastes.
• Recycling today is largely based on the conversion of fertile U-238 to fissile plutonium.
• New reprocessing technologies are being developed to be deployed in conjunction with fast neutron reactors which will burn all long-lived actinides, including all uranium and plutonium, without separating them from one another.
• A significant amount of plutonium recovered from used fuel is currently recycled into MOX fuel; a small amount of recovered uranium is recycled so far.

World-Nuclear: A key, nearly unique, characteristic of nuclear energy is that used fuel may be reprocessed to recover fissile and fertile materials in order to provide fresh fuel for existing and future nuclear power plants. Several European countries, Russia and Japan have had a policy to reprocess used nuclear fuel, although government policies in many other countries have not yet come round to seeing used fuel as a resource rather than a waste.

Over the last 50 years the principal reason for reprocessing used fuel has been to recover unused plutonium, along with less immediately useful unused uranium, in the used fuel elements and thereby close the fuel cycle, gaining some 25% to 30% more energy from the original uranium in the process. This contributes to national energy security. A secondary reason is to reduce the volume of material to be disposed of as high-level waste to about one-fifth. In addition, the level of radioactivity in the waste from reprocessing is much smaller and after about 100 years falls much more rapidly than in used fuel itself.

These are all considerations based on current power reactors, but moving to fourth-generation fast neutron reactors in the late 2020s changes the outlook dramatically, and means that not only used fuel from today’s reactors but also the large stockpiles of depleted uranium (from enrichment plants, about 1.5 million tonnes in 2015) become a fuel source. Uranium mining will become much less significant.

Another major change relates to wastes. In the last decade interest has grown in recovering all long-lived actinides* together (i.e. with plutonium) so as to recycle them in fast reactors so that they end up as short-lived fission products. This policy is driven by two factors: reducing the long-term radioactivity in high-level wastes, and reducing the possibility of plutonium being diverted from civil use – thereby increasing proliferation resistance of the fuel cycle. If used fuel is not reprocessed, then in a century or two the built-in radiological protection will have diminished, allowing the plutonium to be recovered for illicit use (though it is unsuitable for weapons due to the non-fissile isotopes present).

* Actinides are elements 89 to 103, actinium to lawrencium, including thorium, protactinium and uranium as well as transuranics, notably neptunium, plutonium, americium, cerium and californium. The minor actinides in used fuel are all except uranium and plutonium.

Reprocessing used fuela to recover uranium (as reprocessed uranium, or RepU) and plutonium (Pu) avoids the wastage of a valuable resource. Most of it – about 96% – is uranium, of which less than 1% is the fissile U-235 (often 0.4-0.8%); and up to 1% is plutonium. Both can be recycled as fresh fuel, saving up to 30% of the natural uranium otherwise required. The RepU is chiefly valuable for its fertile potential, being transformed into plutonium-239 which may be burned in the reactor where it is formed.

So far, some 90,000 tonnes (of 290,000 t discharged) of used fuel from commercial power reactors has been reprocessed. Annual reprocessing capacity is now about 4500 tonnes per year for normal oxide fuels, but not all of it is operational.

Between 2010 and 2030 some 400,000 tonnes of used fuel is expected to be generated worldwide, including 60,000 t in North America and 69,000 t in Europe.. Read Full At: http://www.world-nuclear.org/

Read More........→January 16, 2016

Nanosubmarines powered by light

Nano-scale submarines built from 244 atoms and capable of moving at 2 cm per second have been demonstrated by Rice University. Credit: Loïc Samuel/Rice University

In a study published by Nano Letters, scientists from Rice University in Texas describe how they built and tested nanoscale submarines, which are able to move with incredible speed. The single-molecule, 244-atom submersibles each have a motor powered by ultraviolet light. With each full revolution the motor's tail-like propeller drives the sub forwards a distance of 18 nanometres (nm). However, the motors run at over a million RPM, giving a top speed of nearly two centimetres (0.8 inches) per second: a breakneck pace on the molecular scale. "These are the fastest-moving molecules ever seen in solution," says chemist James Tour, one of the study authors. While they can't be steered yet, the study has proved that molecular motors are powerful enough to drive the sub-10-nanometre craft through solutions of moving molecules of about the same size. From a nano-scale point of view, "this is akin to a person walking across a basketball court with 1,000 people throwing basketballs at him," Tour said. Tour's group has extensive experience with molecular machines. A decade ago, his lab demonstrated nanocars – single-molecule cars with four wheels, axles and independent suspensions that could be "driven" across a surface. Over the years, many research groups have created microscopic machines featuring motors – but most have either used or generated toxic chemicals. A motor conceived in the last decade by Dutch researchers proved suitable for the Rice submersibles, which were produced in a 20-step chemical synthesis. "These motors are well-known and used for different things," said Victor García-López, lead author and Rice graduate student. "But we were the first to propose they can be used to propel nanocars

Credit: Victor García-López/Rice University

– and now submersibles." The motors, which operate more like a bacteria's flagellum than a propeller, complete each revolution in four steps. When excited by light, the double bond that holds the rotor to the body becomes a single bond, allowing it to rotate a quarter step. As the motor seeks to return to a lower energy state, it jumps adjacent atoms for another quarter turn. This process repeats as long as the light is on. Once built, the team turned to Gufeng Wang at North Carolina State University to measure how well the nanosubs moved. "We had used scanning tunnelling microscopy and fluorescence microscopy to watch our cars drive, but that wouldn't work for the submersibles," explained Tour. "They would drift out of focus pretty quickly." The North Carolina team sandwiched a drop of diluted acetonitrile liquid containing a few nanosubs between two slides, then used a custom confocal fluorescence microscope to hit it from opposite sides with both ultraviolet light (for the motor) and a red laser (for the pontoons). The microscope's laser defined a column of light in the solution, in which tracking occurred, García-López said: "That way, the NC State team could guarantee it was analysing only one molecule at a time." The team hopes future nanosubs will be able to carry cargoes for medical and other purposes. "There's a path forward," García-López said. "This is the first step, and we've proven the concept. Now we need to explore opportunities and potential applications."Nanosubmarines powered by light

Read More........→December 03, 2015

Powering the next billion devices with Wi-Fi

University of Washington engineers have developed a novel technology that uses a Wi-Fi router -- a source of ubiquitous but untapped energy in indoor environments -- to power devices. The Power Over Wi-Fi (PoWiFi) system is one of the most innovative and game-changing technologies of the year, according to Popular Science, which included it in the magazine's annual "Best of What's New" awards announced Wednesday. The technology attracted attention earlier this year when researchers published an online paper showing how they harvested energy from Wi-Fi signals to power a simple temperature sensor, a low-resolution grayscale camera and a charger for a Jawbone activity tracking bracelet. The final paper will be presented next month at the Association for Computing Machinery's CoNEXT 2015 conference in Heidelberg, Germany, on emerging networking experiments and technologies. "For the first time we've shown that you can use Wi-Fi devices to power the sensors in cameras and other devices," said lead author Vamsi Talla, a UW electrical engineering doctoral student. "We also made a system that can co-exist as a Wi-Fi router and a power source -- it doesn't degrade the quality of your Wi-Fi signals while it's powering devices." PoWiFi could help enable development of the Internet of Things, where small computing sensors are embedded in everyday objects like cell phones, coffee makers, washing machines, air conditioners, mobile devices, allowing those devices to "talk" to each other. But one major challenge is how to energize those low-power sensors and actuators without needing to plug them into a power source as they become smaller and more numerous. The team of UW computer science and electrical engineers found that the peak energy contained in untapped, ambient Wi-Fi signals often came close to meeting the operating requirements for some low-power devices. But because the signals are sent intermittently, energy "leaked" out of the system during silent periods. The team fixed that problem by optimizing a router to send out superfluous "power packets" on Wi-Fi channels not currently in use -- essentially beefing up the Wi-Fi signal for power delivery -- without affecting the quality and speed of data transmission. The team also developed sensors that can be integrated in devices to harvest the power. In their proof-of-concept experiments, the team demonstrated that the PoWiFi system could wire-lessly power a gray-scale, low-power Omnivision VGA camera from 17 feet away, allowing it to store enough energy to capture an image every 35 minutes. It also re-charged the battery of a Jawbone Up24 wearable fitness tracker from zero to 41 per cent in 2.5 hours. The researchers also tested the PoWiFi system in six homes. Users typically didn't notice deterioration in web page loading or video streaming experiences, showing the technology could successfully deliver power via Wi-Fi in real-world conditions without degrading network performance. Although initial experiments harvested relatively small amounts of power, the UW team believes there's opportunity for make the PoWiFi system more efficient and robust. "In the future, PoWi-Fi could leverage technology power scaling to further improve the efficiency of the system to enable operation at larger distances and power numerous more sensors and applications," said co-author Shyam Gollakota, assistant professor of computer science and engineering. Source: Article, Source: flickr.com

Read More........→November 20, 2015