Free Newsletters - Space News - Defense Alert - Environment Report - Energy Monitor
. Earth Science News .




BLUE SKY
Scientists measure soot particles in flight
by Staff Writers
Berlin, Germany (SPX) Jun 29, 2012


This image shows the diffraction pattern of a single soot particle. Credit: Duane Loh et al.

"For the first time we can actually see the structure of individual aerosol particles floating in air, their 'native habitat'," said DESY scientist Henry Chapman from the Center for Free-Electron Laser Science (CFEL) in Hamburg. "This will have important implications for various fields from climate modelling to human health." CFEL is a joint venture of Deutsches Elektronen-Synchrotron DESY, the German Max Planck Society and the University of Hamburg.

Aerosol particles like soot play important roles in a wide range of fields from toxicology to climate science. Despite their importance, their properties are surprisingly difficult to measure: Visible light doesn't provide the necessary resolution, X-ray sources are usually not bright enough to image single particles, and for electron microscopy particles have to be collected onto a substrate, which potentially alters their structure and encourages agglomeration.

Using the world's most powerful X-ray laser LCLS at the U.S. SLAC National Accelerator Laboratory in Stanford (California), the team captured images of single soot particles floating through the laser beam.

"We now have a richer imaging tool to explore the connections between their toxicity and internal structure," said SLAC's Duane Loh, lead author of the study appearing in this week's scientific journal Nature. Free-electron lasers like LCLS or the European XFEL currently being built in Hamburg consist of particle accelerators that send unbound (free) electrons on a tight slalom course where they emit X-ray light.

The study focused on particles less than 2.5 micrometres in diameter. This is the size range of particles that efficiently transport into the human lungs and constitute the second most important contribution to global warming. Microscopic soot particles were generated with electric sparks from a graphite block and fed with a carrier gas of argon and nitrogen into a device called an aerodynamic lens, that produces a thin beam of air with entrained soot particles.

This aerosol beam intercepted the pulsed laser beam. Whenever an X-ray laser pulse hit a soot particle, it produced a characteristic diffraction pattern that was recorded by a detector. From this pattern, the scientists were able to reconstruct the soot particle's structure.

"The structure of soot determines how it scatters light, which is an important part of understanding how the energy of the sun is absorbed by the earth's atmosphere. This is a key factor in models of the earth's climate," explained co-author Andrew Martin from DESY.

"There also are many links between airborne particles around two micrometres in size and adverse health effects. Using the free-electron laser we are now able to measure the shape and composition of individual airborne particles. This may lead to a better understanding of how these particles interfere with the function of cells in the lungs."

The team recorded patterns from 174 individual soot particles and measured their compactness, using a property called fractal dimension. "We've seen that the fractal dimension is higher than what was thought," said Chapman.

"This means that soot in the air is compact, which has implications for the modelling of climate effects." Also, the structure of the airborne soot seems to be surprisingly variable. "There is quite some variation in the fractal dimension, which implies that a lot of rearrangement is going on in the air," explains Chapman.

A primary long-term goal of the research is to take snapshots of airborne particles as they change their size, shape and chemical make-up in response to their environment, explained Michael Bogan from SLAC, who led the research. "Scientists can now imagine being able to watch the evolution of soot formation in combustion engines from their molecular building blocks, or maybe even view the first steps of ice crystal formation in clouds."

In real-world settings soot is seldom pure. To see the effects of mixing with other aerosols, the researchers added salt spray to the soot particles, resulting in larger particles with soot attached to the tiny salt crystals. Such composite particles might form in coastal cities and are expected to have a much larger climate effect than soot alone.

Composite aerosols are more difficult to analyse, but the new technique could clearly discern between soot, salt and mixtures of both. As the aerosol particles are vaporized by the intense X-ray laser pulse, the researchers could use mass spectroscopy to examine the composition of each individual particle imaged.

Even though the aerosol particles are destroyed by the X-ray laser pulse, the pulse is so short that it out-runs this destruction. Therefore the diffraction patterns are of high quality and represent the undamaged object.

The novel X-ray technique can find wide application to study all sorts of aerosols and can also be extended to resolve the static and dynamic morphology of general ensembles of disordered particles, the researchers state.

"We are now able to study the structure of soot by measuring individual particles in a large ensemble," explains Martin. "Biological samples, like cells and large proteins, have a similar size to the soot particles we studied and also lack a fixed, reproducible structure. In the future it may be possible to extend these techniques beyond aerosols, to study the structural variations in biological systems."

The research team included contributors from SLAC, DESY, Lawrence Berkeley National Laboratory, the Max Planck Institutes, the National Energy Research Scientific Computing Center, Lawrence Livermore National Laboratory, Cornell University, the University of Hamburg, Synchrotron Trieste and Uppsala University. LCLS is supported by DOE's Office of Science.

.


Related Links
Helmholtz Association of German Research Centres
The Air We Breathe at TerraDaily.com






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





BLUE SKY
2012 Noctilucent Cloud Season Begins
Huntsville AL (SPX) Jun 25, 2012
Data from NASA's AIM spacecraft show that noctilucent clouds (NLCs) are like a great "geophysical light bulb". They turn on every year in late spring, reaching almost full intensity over a period of no more than 5 to 10 days--and the bulb is glowing. "They were visible to the north for about 3 hours as we flew between Ottawa and Newfoundland at 35,000 feet" said Brian Whittaker. Thes ... read more


BLUE SKY
20 killed as fuel truck crash in China sparks fire

Record radiation levels detected at Fukushima reactor

Eviction pits Haiti police against protestors

Population displacement during disasters predicted using mobile data

BLUE SKY
Better surfaces could help dissipate heat

Japan finds major rare earth deposits: researcher

Boeing helps open thermoplastic composites research lab in the Netherlands

France pulls plug on Internet forerunner Minitel

BLUE SKY
Saving the Baltic Sea

Dying trees in Southwest set stage for erosion, water loss in Colorado River

Research Vessel Winds Down Visit to Vietnam

Senator expects US to ratify sea treaty

BLUE SKY
Scientists to produce first 3-D models of Arctic sea ice

Canada builds up arctic region defenses

Greenland ice may exaggerate magnitude of 13,000-year-old deep freeze

Emperor penguins threatened by Antarctic sea ice loss

BLUE SKY
Most new pesticides have roots in natural substances

Taiwan tea a matter of passion and profit

A new source of maize hybrid vigor

France slaps ban on Swiss pesticide as bee threat

BLUE SKY
Floods swamp eastern India, 1.3 million displaced

UCSB scientists compile first study of potential for tsunamis in northwestern California

NASA chooses University professors for $151.7 million mission

Debby hits land as Florida braces for more floods

BLUE SKY
UNESCO warns Timbuktu in danger amid Mali unrest

Shell says close to launch of test drilling off Guiana coast

New revolt escalates endless DRC war

Hotel inside S.Africa's Kruger Park irks conservationists

BLUE SKY
Outside View: 18th-century words for today

Did pre-human diet choice affect survival?

'Brain-hacking' technology sought

Out of the mouths of primates, facial mechanics of human speech may have evolved




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement