Monday, April 9, 2012

Getting to the moon on drops of fuel

 Imagine reaching the Moon using just a fraction of a liter of fuel. With their ionic motor, MicroThrust, EPFL scientists and their European partners are making this a reality and ushering in a new era of low-cost space exploration. The complete thruster weighs just a few hundred grams and is specifically designed to propel small (1-100 kg) satellites, which it enables to change orbit around Earth and even voyage to more distant destinations -- functions typically possible only for large, expensive spacecraft. The just-released prototype is to be employed on CleanSpace One, a satellite under development at EPFL that is designed to clean up space debris, and on OLFAR, a swarm of Dutch nanosatellites that will record ultra-low radio-frequency signals on the far side of the Moon.

The motor, designed to be mounted on satellites as small as 10x10x10 cm3, is extremely compact but highly efficient. The prototype weighs only about 200 grams, including the fuel and control electronics.

"At the moment, nanosatellites are stuck in their orbits. Our goal is to set them free," explains Herbert Shea, coordinator of the European MicroThrust project and director of EPFL's Microsystems for Space Technologies Laboratory.

Small satellites are all the rage right now because their manufacturing and launch costs are relatively low -- about half a million dollars, compared to conventional satellites that run into the hundreds of millions. But nanosatellites currently lack an efficient propulsion system that would render them truly autonomous and thus able to carry out exploration or observation missions.

A motor that doesn't burn fuel

Instead of a combustible fuel, the new mini motor runs on an "ionic" liquid, in this case the chemical compound EMI-BF4, which is used as a solvent and an electrolyte. It is composed of electrically charged molecules (like ordinary table salt) called ions, except that this compound is liquid at room temperature. The ions are extracted from the liquid and then ejected by means of an electric field to generate thrust. This is the principle behind the ionic motor: fuel is not burned, it is expelled.

In the motor developed at EPFL, the flow of ions is emitted from an array of tiny silicon nozzles -- over 1,000 per square centimeter. The fuel is first guided by capillary action from a reservoir to the extremity of the micro-nozzles, where the ions are then extracted by an electrode held at 1,000 volts, accelerated, and finally emitted out the back of the satellite. The polarity of the electric field is reversed every second, so that all the ions -- positive and negative -- are ejected.

SystematIC Design, a MicroThrust project partner, designed the motor's electrical system. The ion ejection system requires a high electrical voltage, but the available energy aboard a 1-liter nanosatellite is limited to a few small solar cells -- in practice, about four watts of power. The Dutch company was able to develop a system that overcame this difficulty.

Cruising speed: 40,000 km per hour

After six months of acceleration, the microsatellite's speed increases from 24,000 km/h, its launch speed, to 42,000 km/h. The acceleration is only about a tenth of a millimeter per square second, which translates into 0-100 km/h in 77 hours. But in space, where there is no friction to impede motion, gentle but steady acceleration is the way to go.

The ionic motor will power CleanSpace One -- a nanosatellite whose mission is to tidy up space by grabbing space debris and pulling it into Earth's atmosphere to be safely incinerated. According to the Swiss Space Center, CleanSpace One will take two to three months and more than 1,000 terrestrial revolutions to reach one of its targets, the decommissioned Swisscube cubesat or Tlsat-1 cubesat. Scientists have just over a year to finalize their system.

Researchers have a bit more than a year to finalize the ionic motor. The prototype was developed in the context of a European project coordinated by EPFL and involved Queen Mary and Westfield College in the UK, the Dutch companies TNO and SystematIC Design B.V., and Nanospace AB in Sweden.

Story Source:

The above story is reprinted from materials provided by Ecole Polytechnique Fédérale de Lausanne.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Scientists unlock key to cancer cell death mystery

A group led by the University of Leicester has shown that particular cancer cells are especially sensitive to a protein called p21. This protein usually forces normal and cancer cells to stop dividing but it was recently shown that in some cases it can also kill .

However, scientists have been unclear about how this happens.

Researcher Salvador Macip, from the University of Leicester Department of Biochemistry, said: "If we could harness this 'killing power' that p21 has, we could think of designing new therapies aimed at increasing its levels in tumours. This is what motivated us to look into it".

Now the team from the universities of Leicester and Cardiff in the UK, University of South Carolina, USA and Karolinska Institutet, Sweden has discovered that cells from sarcomas tend to die in response to p21 and that this is determined by the sensitivity of their to oxidants.

They have published their findings in The . The research was funded by the MRC, the NIH, CONACYT and the Swedish Cancer Society

Dr Macip added: "Our research also showed that p21 can kill cells even in the absence of p53, a protein that is in the main responsible for but is inactivated in most cancers.

"This shows that certain , sarcomas for instance, but maybe also others, should respond well to drugs that increase the levels of p21, even if they don't have an active . The side effects of these therapies should be minimal, since our experiments show that normal cells would arrest but not die in response to p21.

"There are already drugs available that selectively increase p21. Our results provide a rationale for testing them in certain types of cancers, which could be identified using the experiments we describe."

More information: Reactive oxygen species and mitochondrial sensitivity to oxidative stress determine induction of cancer cell death by p21. Masgras I, Carrera S, de Verdier PJ, Brennan P, Majid A, Makhtar W, Tulchinksy E, Jones GD, Roninson IB, Macip S. J Biol Chem. 2012 Feb 6. [Epub ahead of print]

The Journal of Biological Chemistry, Vol. 287, Issue 13, 9845-9854, MARCH 23, 2012

Provided by University of Leicester (news : web)

Modified microbes turn carbon dioxide to liquid fuel

Today, electrical energy generated by various methods is still difficult to store efficiently. Chemical batteries, hydraulic pumping and water splitting suffer from low energy-density storage or incompatibility with current transportation infrastructure.

In a study published March 30 in the journal Science, James Liao, UCLA's Ralph M. Parsons Foundation Chair in Chemical Engineering, and his team report a method for storing electrical energy as chemical energy in higher alcohols, which can be used as liquid transportation fuels.

"The current way to store is with lithium ion batteries, in which the density is low, but when you store it in liquid fuel, the density could actually be very high," Liao said. "In addition, we have the potential to use electricity as transportation fuel without needing to change current infrastructure."

Liao and his team genetically engineered a lithoautotrophic microorganism known as Ralstonia eutropha H16 to produce and 3-methyl-1-butanol in an electro-bioreactor using carbon dioxide as the sole carbon source and electricity as the sole energy input.

Photosynthesis is the process of converting light energy to chemical energy and storing it in the bonds of sugar. There are two parts to photosynthesis — a light reaction and a dark reaction. The light reaction converts light energy to chemical energy and must take place in the light. The dark reaction, which converts CO2 to sugar, doesn't directly need light to occur.

"We've been able to separate the light reaction from the dark reaction and instead of using biological photosynthesis, we are using solar panels to convert the sunlight to electrical energy, then to a chemical intermediate, and using that to power fixation to produce the fuel," Liao said. "This method could be more efficient than the biological system."

Liao explained that with biological systems, the plants used require large areas of agricultural land. However, because Liao's method does not require the light and dark reactions to take place together, solar panels, for example, can be built in the desert or on rooftops.

Theoretically, the hydrogen generated by solar electricity can drive CO2 conversion in lithoautotrophic microorganisms engineered to synthesize high-energy density liquid fuels. But the low solubility, low mass-transfer rate and the safety issues surrounding hydrogen limit the efficiency and scalability of such processes. Instead Liao's team found formic acid to be a favorable substitute and efficient energy carrier.

"Instead of using hydrogen, we use formic acid as the intermediary," Liao said. "We use electricity to generate formic acid and then use the formic acid to power the CO2 fixation in bacteria in the dark to produce isobutanol and higher alcohols."

The electrochemical formate production and the biological CO2 fixation and higher alcohol synthesis now open up the possibility of electricity-driven bioconversion of CO2 to a variety of chemicals. In addition, the transformation of formate into liquid fuel will also play an important role in the biomass refinery process, according to Liao.

"We've demonstrated the principle, and now we think we can scale up," he said. "That's our next step."

More information: "Integrated Electromicrobial Conversion of CO2 to Higher Alcohols," by H. Li; D.G. Wernick, Science.

Provided by University of California Los Angeles (news : web)

New process converts polyethylene into carbon fiber

Common material such as polyethylene used in plastic bags could be turned into something far more valuable through a process being developed at the Department of Energy's Oak Ridge National Laboratory.

In a paper published in Advanced Materials, a team led by Amit Naskar of the Materials Science and Technology Division outlined a method that allows not only for production of carbon fiber but also the ability to tailor the final product to specific applications.

"Our results represent what we believe will one day provide industry with a flexible technique for producing technologically innovative fibers in myriad configurations such as fiber bundle or non-woven mat assemblies," Naskar said.

Using a combination of multi-component fiber spinning and their sulfonation technique, Naskar and colleagues demonstrated that they can make polyethylene-base fibers with a customized surface contour and manipulate filament diameter down to the submicron scale. The patent-pending process also allows them to tune the porosity, making the material potentially useful for filtration, catalysis and electrochemical energy harvesting.

Naskar noted that the sulfonation process allows for great flexibility as the carbon fibers exhibit properties that are dictated by processing conditions. For this project, the researchers produced carbon fibers with unique cross-sectional geometry, from hollow circular to gear-shaped by using a multi-component melt extrusion-based fiber spinning method.

The possibilities are virtually endless, according to Naskar, who described the process.

"We dip the fiber bundle into an acid containing a chemical bath where it reacts and forms a black fiber that no longer will melt," Naskar said. "It is this sulfonation reaction that transforms the plastic fiber into an infusible form.

"At this stage, the plastic molecules bond, and with further heating cannot melt or flow. At very high temperatures, this fiber retains mostly carbon and all other elements volatize off in different gas or compound forms."

The researchers also noted that their discovery represents a success for DOE, which seeks advances in lightweight materials that can, among other things, help the U.S. auto industry design cars able to achieve more miles per gallon with no compromise in safety or comfort. And the raw material, which could come from grocery store plastic bags, carpet backing scraps and salvage, is abundant and inexpensive.

Story Source:

The above story is reprinted from materials provided by DOE/Oak Ridge National Laboratory.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Marcus Hunt, Tomonori Saito, Rebecca Brown and Amar Kumbhar. Patterned functional carbon fibers from polyethylene. Advanced Materials, 2012 DOI: 10.1002/adma.201104551

New nano-measurements add spark to centuries-old theory of friction

 The phenomenon of friction, when studied on a nanoscale, is more complex than previously thought. When friction occurs, an object does not simply slide its surface over that of another, it also makes a slight up-and-down movement. This finding completes a centuries-old theory of friction dating to 1699 and uncovers a gap in contemporary thinking on friction. The phenomenon -- termed lift-up hysteresis -- was described in a recent study by researchers Farid Al-Bender, Kris De Moerlooze and Paul Vanherck of the Production Engineering, Machine Design and Automation Division at KU Leuven's Department of Mechanical Engineering.

Friction is the force that occurs when one surface slides over another, or when an object moves through a liquid or a gas. Until now, the theory explaining the phenomenon of friction was fragmented. French physicists Guillaume Amontons and Charles August Coulomb, working in the late-17th and mid-18th centuries, respectively, strove to find an explanation for frictional resistance. Frictional resistance explains, for instance, why gliding a heavy cabinet across a floor is much more difficult than gliding a chair. As the weight of an object increases, so too does the resistance. The floor and the bottom of the cabinet move against one another from left to right or vice versa. But at the same time the weight of the cabinet bears perpendicularly upon the bottom of the cabinet and the floor. This normal load -- 'normal' in the sense of being perpendicular to the direction of shifting -- pushes the two surfaces together and produces resistance as friction occurs. If we put the chair and the cabinet on wheels and push them uphill, more force is needed to move the cabinet than to move the chair.

Using this reasoning, Amontons and Coulomb explained friction by the roughness of both surfaces: the (sometimes microscopically small) nooks and crannies of one surface -- asperities -- which settle upon those of another when one object rests upon another. When friction occurs, these asperities play the role of slopes. They are made to climb, descend and deform so that movement can continue, similar to what happens when the bristles of two brushes rub together. This theory is sometimes called the 'bump hypothesis' because one surface grinds over the bumps of another with an up-and-down movement.

In the 20th century it became clear that the existing theory did not fully correspond with the laws of thermodynamics, the science that studies the conversion of heat into mechanical energy or vice versa. Specifically, Amontons and Coulomb's bump hypothesis failed to explain energy lost as a result of friction. In their theory, the sum of the energy needed to go 'uphill' and then 'downhill' is zero. At the same time, we know that pure surfaces have an electro-chemical tendency to stick to each other. This is caused by asperities being stuck to one another in a phenomenon called adhesion. A typical example is Scotch tape. When movement occurs, all the bonds between the asperities of the two surfaces are broken and reformed elsewhere. Consequently, factors such as speed and acceleration influence friction. With the rise of the newer adhesion theory, Amontons and Coulomb's theory gradually faded into oblivion. But the modern adhesion theory of friction was shown to have inconsistencies of its own.

Normal motion, nano-scale Micro- and nano-scale measurement techniques now allow researchers to study friction at an atomic level. Professor Farid Al-Bender and his team conducted an experiment with extremely precise friction and displacement sensors and tested various materials (paper, plastic and brass) at different speeds of movement. The results map out frictional force measurements consistent with those predicted by adhesion theory. But until now, 'normal motion' -- movement perpendicular to the rubbing movement -- had not yet been measured. While normal motion amounts to a mere 5 -- 50 nanometers -- billionths of a meter -- this systematic up-and-down motion had previously been overlooked. Measurements of this normal motion, say the KU Leuven researchers, confirms the centuries-old hypothesis of asperity deformation and slope pioneered by Amontons and Coulomb and paints a more complex picture of the phenomenon of friction because normal motion must now be taken into account when developing a comprehensive theory of friction. Al-Bender and his team's results suggest that friction is caused by an interaction of both adhesion on the one hand and asperity deformation and slope on the other.

Tribology Tribology -- the science of friction, lubrication and wear -- is an important area of mechanical engineering. Tribology research can help lower economic and environmental costs of production and usage. If the interaction between moving surfaces can be controlled, time and energy inputs can be optimised and wear-and-tear, malfunctions and waste can be reduced. Tribology research can also contribute to the miniaturisation of products, such as computer components. At KU Leuven, research in tribology is closely linked with research in mechanical engineering, machine design, materials science and robotics.

Story Source:

The above story is reprinted from materials provided by Katholieke Universiteit Leuven, via AlphaGalileo.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Farid Al-Bender, Kris Moerlooze, Paul Vanherck. Lift-up Hysteresis Butterflies in Friction. Tribology Letters, 2012; 46 (1): 23 DOI: 10.1007/s11249-012-9914-y