MC²

October 7, 2009

Electron microscopes are the most powerful type of microscope, capable of distinguishing even individual atoms. However, these microscopes cannot be used to image living cells because the electrons destroy the samples.

Now, MIT assistant professor Mehmet Fatih Yanik and his student, William Putnam, propose a new scheme that can overcome this limitation by using a quantum mechanical measurement technique that allows electrons to sense objects remotely. Damage would be avoided because the electrons would never actually hit the imaged objects.

Such a non-invasive electron microscope could shed light on fundamental questions about life and matter, allowing researchers to observe molecules inside a living cell without disturbing them. Yanik and Putnam report their new approach in the October issue of Physical Review A — Rapid Communications.

If successful, such microscopes would surmount what Nobel laureate Dennis Gabor concluded in 1956 was the fundamental limitation of electron microscopy: “the destruction of the object by the exploring agent.”

Electron flow

Electron microscopes use a particle beam of electrons, instead of light, to image specimens. Resolution of electron microscope images ranges from 0.2 to 10 nanometers — 10 to 1,000 times greater than a traditional light microscope. Electron microscopes can also magnify samples up to two million times, while light microscopes are limited to 2,000 times.

However, biologists have been unable to unleash the high power of electron microscopes on living specimens, because of the destructive power of the electrons.

The radiation dose received by a specimen during electron microscope imaging is comparable to the irradiation from a 10-megaton hydrogen bomb exploded about 30 meters away. When exposed to such energetic electron beams, biological specimens experience rapid breakdown, modification of chemical bonds, or other structural damages.

Although there exist special chambers to keep biological samples in a watery environment within the high vacuum required for electron microscopes, chemical preservation or freezing, which kill cells, is still required before biological samples can be viewed with existing electron microscopes.

In the proposed quantum mechanical setup, electrons would not directly strike the object being imaged. Instead, an electron would flow around one of two rings, arranged one above the other. The rings would be close enough together that the electron could hop easily between them. However, if an object (such as a cell) were placed between the rings, it would prevent the electron from hopping, and the electron would be trapped in one ring.

This setup would scan one “pixel” of the specimen at a time, putting them all together to create the full image. Whenever the electron is trapped, the system would know that there is a dark pixel in that spot.

Though technical challenges would need to be overcome (such as preventing the imaging electron from interacting with electrons of the metals in the microscope), Yanik believes that eventually such a microscope could achieve a few nanometers of resolution. That level of resolution would allow scientists to view molecules such as enzymes in action inside living cells, and even single nucleic acids — the building blocks of DNA.

Yanik, the Robert J. Shillman Career Development Assistant Professor of Electrical Engineering, says he expects the work will launch experimental efforts that could lead to a prototype within the next five years.

Charles Lieber, professor of chemistry at Harvard and an expert in nanoscale technology, describes Yanik’s proposal as a “highly original and exciting concept for ‘noninvasive’ high-resolution imaging” using an electron microscope.

“From my perspective, it has the potential to be a breakthrough for those working with sensitive samples, such as biological imaging,” Lieber says. “Also, in general terms I find his work intellectually exciting because it is not incremental but takes a quantum (excuse the pun) jump forward through creative thinking.”

Source:

• Massachusetts Institute of Technology, Retrieved 10/7/2009 from: http://web.mit.edu/

October 7, 2009

It’s often the little things that count in industrial manufacturing processes. Particles less than half the diameter of a hair in size can significantly impair quality in production. For example, there should be no particles larger than five micrometers on the packaging film of food and medicines, as these could contaminate the contents.

Tiny particles also cause problems in the printing industry, as they reduce the quality of the print if they remain on the surface of the paper. And fine particles on electrical components can cause operational failures.

Manufacturers usually resort to a type of vacuum cleaner to remove the dust – it blows air on the contaminated surface, then sucks this in again, together with the undesired particles. However, this method does not effectively remove particles smaller than 20 micrometers, as the electrostatic force causes the majority of them to remain on the surface.

Researchers at the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB in Stuttgart have developed a system which also removes these fine dust particles effectively from the product surfaces. Colleagues from NITO A/S in Denmark, Ziegener + Frick GmbH in Ellhofen and the Danish Innovation Institute were involved in the development process.

“The system guarantees the quality of the product and improves the working environment of employees, as it reliably collects the harmful particles, preventing them from going into the air and then into the lungs of employees,“ says Sukhanes Laopeamthong, a researcher at the IGB.

The researchers charge the dust particles with positive ions. A negatively charged electrode attracts the positively charged dust particles, the resulting force lifting the dust particles easily from the surface of the product. A controlled air current carries them to the dust collector. Prior to the construction of the test equipment, the researchers have already resolved a few questions using special simulation software.

What electrical field strength is required to lift the dust particles? What are the required characteristics of the air current transporting the particles? The test equipment removes on average 85 percent of dust particles smaller than 15 micrometers and more than 95 percent of dust particles bigger than 15 micrometers. The researchers are presenting the exhibit at the Parts2Clean trade fair from 20 to 22 October in Stuttgart (hall 1, stand F 610/G 709). The scientists expect the system to be operational in industry in approximately two years.

Source:

• Fraunhofer-Gesellschaft, Retrieved 10/7/2009 from: http://www.fraunhofer.de/

October 7, 2009

NASA’s Spitzer Space Telescope has discovered an enormous ring around Saturn — by far the largest of the giant planet’s many rings.

The new belt lies at the far reaches of the Saturnian system, with an orbit tilted 27 degrees from the main ring plane. The bulk of its material starts about six million kilometers (3.7 million miles) away from the planet and extends outward roughly another 12 million kilometers (7.4 million miles). One of Saturn’s farthest moons, Phoebe, circles within the newfound ring, and is likely the source of its material.

Saturn’s newest halo is thick, too — its vertical height is about 20 times the diameter of the planet. It would take about one billion Earths stacked together to fill the ring.

“This is one supersized ring,” said Anne Verbiscer, an astronomer at the University of Virginia, Charlottesville. “If you could see the ring, it would span the width of two full moons’ worth of sky, one on either side of Saturn.” Verbiscer; Douglas Hamilton of the University of Maryland, College Park; and Michael Skrutskie, of the University of Virginia, Charlottesville, are authors of a paper about the discovery to be published online tomorrow by the journal Nature.

An artist’s concept of the newfound ring is online at http://www.nasa.gov/mission_pages/spitzer/multimedia/spitzer-20091007a.html .

The ring itself is tenuous, made up of a thin array of ice and dust particles. Spitzer’s infrared eyes were able to spot the glow of the band’s cool dust. The telescope, launched in 2003, is currently 107 million kilometers (66 million miles) from Earth in orbit around the sun.

The discovery may help solve an age-old riddle of one of Saturn’s moons. Iapetus has a strange appearance — one side is bright and the other is really dark, in a pattern that resembles the yin-yang symbol. The astronomer Giovanni Cassini first spotted the moon in 1671, and years later figured out it has a dark side, now named Cassini Regio in his honor. A stunning picture of Iapetus taken by NASA’s Cassini spacecraft is online at http://photojournal.jpl.nasa.gov/catalog/PIA08384 .

Saturn’s newest addition could explain how Cassini Regio came to be. The ring is circling in the same direction as Phoebe, while Iapetus, the other rings and most of Saturn’s moons are all going the opposite way. According to the scientists, some of the dark and dusty material from the outer ring moves inward toward Iapetus, slamming the icy moon like bugs on a windshield.

“Astronomers have long suspected that there is a connection between Saturn’s outer moon Phoebe and the dark material on Iapetus,” said Hamilton. “This new ring provides convincing evidence of that relationship.”

Verbiscer and her colleagues used Spitzer’s longer-wavelength infrared camera, called the multiband imaging photometer, to scan through a patch of sky far from Saturn and a bit inside Phoebe’s orbit. The astronomers had a hunch that Phoebe might be circling around in a belt of dust kicked up from its minor collisions with comets — a process similar to that around stars with dusty disks of planetary debris. Sure enough, when the scientists took a first look at their Spitzer data, a band of dust jumped out.

The ring would be difficult to see with visible-light telescopes. Its particles are diffuse and may even extend beyond the bulk of the ring material all the way in to Saturn and all the way out to interplanetary space. The relatively small numbers of particles in the ring wouldn’t reflect much visible light, especially out at Saturn where sunlight is weak.

“The particles are so far apart that if you were to stand in the ring, you wouldn’t even know it,” said Verbiscer.

Spitzer was able to sense the glow of the cool dust, which is only about 80 Kelvin (minus 316 degrees Fahrenheit). Cool objects shine with infrared, or thermal radiation; for example, even a cup of ice cream is blazing with infrared light. “By focusing on the glow of the ring’s cool dust, Spitzer made it easy to find,” said Verbiscer.

These observations were made before Spitzer ran out of coolant in May and began its “warm” mission.

NASA’s Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA’s Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology, also in Pasadena. Caltech manages JPL for NASA. The multiband imaging photometer for Spitzer was built by Ball Aerospace Corporation, Boulder, Colo., and the University of Arizona, Tucson. Its principal investigator is George Rieke of the University of Arizona.

For additional images relating to the ring discovery and more information about Spitzer, visit http://www.spitzer.caltech.edu and http://www.nasa.gov/spitzer .

Source:

• NASA/Jet Propulsion Laboratory, Retrieved 10/7/2009 from: http://www.jpl.nasa.gov/

October 7, 2009
IMEC, one of the leading European research centers in photovoltaics, and BP Solar, a leading energy company, demonstrated a 18% conversion efficiency for silicon solar cells made of BP Solar’s newly developed Mono2TM silicon. By combining IMEC’s advanced processing techniques with BP Solar’s high-quality low-cost substrates, the companies demonstrated that Mono2 has a [...]

October 7, 2009
Researchers have created a CMOS (semiconductor) camera capable of filming individual photons one million times a second.
The scientists wanted to create the fastest, highest resolution CMOS (semiconductor) video camera, but to do that they needed to choose an ultra-fast photo detector. They also needed to choose between two competing timing mechanisms or stopwatches, [...]

October 6, 2009
Crashing a rocket into the Moon will create “one more dimple” on the lunar surface and could find water ice on Earth’s nearest neighbour, according to a Durham University expert.
Dr Vincent Eke’s research has helped inform NASA’s decision about where to crash its probes into the Moon’s surface in search of water.
The Lunar [...]

October 6, 2009
Some stars are lonely behemoths, with no surrounding planets or asteroids, while others sport a skirt of attendant planetary bodies. New research published this week in The Astrophysical Journal Letters explains why the composition of the stars often indicates whether their light shines into deep space, or whether a small fraction shines onto [...]

October 6, 2009
Billions of tonnes of water droplets vanish from the atmosphere in events that reveal in detail how the Sun and the stars control our everyday clouds. Researchers of the National Space Institute in the Technical University of Denmark (DTU) have traced the consequences of eruptions on the Sun that screen the Earth from [...]

October 6, 2009
High-energy heavy ion collisions, which are studied at RHIC in Brookhaven and soon at the LHC in Geneva, can be a source of light flashes of a few yoctoseconds duration (a septillionth of a second, 10-24 s, or ys for short) — the time that light needs to traverse an atomic nucleus. This [...]

October 6, 2009
Small bits of metal may play a new role in solar power.
Researchers at Ohio State University are experimenting with polymer semiconductors that absorb the sun’s energy and generate electricity. The goal: lighter, cheaper, and more-flexible solar cells.
They have now discovered that adding tiny bits of silver to the plastic boosts the materials’ electrical [...]