Our summer session of Physics 53 begins Monday with the largest class we have hosted in my 5 years at DUML. Thirty eight students will begin their study of mechanics and will progress through fluids, mechanical waves, and thermodynamics in five short weeks of intensive study. This brief article seemed appropriate for a first blog entry of the session. First of all, because it combines forces and oscillations, which are two of our principle areas of study. Of course, there are a few insects in and around the wetlands which are so prevalent around our island paradise. I propose listening to the audio files contained in the Clarkson University study while we try to avoid the local bugs. Here’s to a buzz free summer session!
(PhysOrg.com) — A team of Clarkson University scientists led by Prof. Igor Sokolov are using atomic force microscopy (AFM) to record sounds emanating from inside living insects like flies, mosquitoes and ladybugs.
AFM is one of major scientific tools responsible for the emergence of modern nanotechnology. The unprecedented sensitivity of AFM allowed the Clarkson team to record sub-nano oscillations of very faint amplitude (less than the size of one atom) at high frequencies (up to 1,000 hertz or cycles per second). Previous work in the study of insects was only done at up to 5 hertz. The sounds are recorded by touching the surface of the bugs with an AFM probe. The study of these sounds may allow researchers to discover unknown features and physiology of insects. Sokolov hopes these discoveries may help in finding solutions to the problems caused by insect pests. “Insects are of general interest not only as the most numerous and diverse group of animals on the planet, but also as highly efficient bio-machines varying greatly in size,” says Sokolov. “Some are major agricultural pests and competitors of humans for crops. Mosquitoes and other insects are important vectors of plant, animal, and human diseases. Also, vast lands of the earth are still underdeveloped because they are occupied by blood-sucking insects.” You can listen to audio files of the internal sounds of mosquitoes, flies, and ladybugs: //
// The Sokolov team’s research is published in the top journal of applied physics, Applied Physics Letters, at http://apl.aip.org/applab/v96/i4/p043701_s1 .The team consisted of Sokolov, who has appointments in Physics, and Chemistry and Biomolecular Science; Maxim Dokukin, a physics postdoctoral fellow; and Nataliia Guz, a physics graduate student; and Sergey Vasilyev, instrumental scientist. The other members of Sokolov’s group, physics graduate students Dmytro Volkov, Ravi Gaikwad, and Shyuzhene Li, work on biosensors, self-assembly of particles, and the study of skin aging.
In the “information age”, data abounds and much of it is publicly funded. Hans Rosling presents data in a visually stimulating manner, tracking stats for countries over time and arguing for far better use and display and availability of data. Great TED talk!
Wendy is about to complete our “physics 54” via video-link to Dr. Brown’s physics 42 lectures combined with some study and recitation time with me (the physics coordinator/glorified TA at DUML). As Wendy gets prepared for her final exam, I have been thinking about data for the DUML physics students. What metrics can be developed to evaluate the effectiveness of our DUML presentation of physics?
Along another line of thought — what software tools might be added to the physics computers to allow for more sophisticated analysis and presentation of data without adding to the instructional load of a very fast paced summer session?
Tiny, ubiquitous particles in the atmosphere may play a profound role in regulating global climate. But the scientists who study these particles — called aerosols — have long struggled to accurately measure their composition, size, and global distribution. A new detection technique and a new satellite instrument developed by NASA scientists, the Aerosol Polarimetry Sensor (APS), should help ease the struggle.
Some types of small aerosols — such as black carbon from motor vehicle exhaust and biomass burning — promote atmospheric warming by absorbing sunlight. Others, such as sulfates from coal-fired power plants, exert a cooling effect by reflecting incoming solar radiation back into space. Overall, aerosols present one of the greatest areas of uncertainty in understanding what drives climate change.
But quantifying the influence of aerosols on the atmosphere and climate has been hampered by difficulties in measuring the aerosols themselves. The problem is especially acute over land, where the glare from sunlight reflecting off Earth’s surface overwhelms the passive imaging instruments scientists typically use to detect aerosols.
In recent years, however, researchers from NASA Goddard’s Institute for Space Studies (GISS) in New York City have developed new remote-sensing techniques to more accurately measure aerosols over land.
The Research Scanning Polarimeter (RSP), an aircraft-based version of APS, is the first such instrument to measure polarized light at one particularly important wavelength (2.2 micrometers). “The 2.2 micrometer channel is critical because it provides the only passive method we have to retrieve accurate and detailed aerosol properties over land surfaces,” said Michael Mishchenko, Glory’s project scientist.
RSP uses crystal prisms to effectively filter out the bright glare from Earth’s surface, functioning somewhat like polarized sunglasses by only allowing light waves oriented in specific directions to pass.
According to Brian Cairns, an aerosol climatologist at GISS who has pioneered the technique, polarized images have a dull tone that make the subtle hues of aerosols easier to detect amidst the shades of gray land.
“The blueish tint of small aerosols in the atmosphere is more clearly distinguishable with polarized light,” Cairns said.
The new retrieval technique also integrates more information about short-wave polarized light into models used to determine aerosol properties. Past approaches have left short-wave polarized light — which is crucial for calculating how high aerosols reside in the atmosphere and how much radiation the particles are absorbing — largely out of the equation.
RSP is not the first instrument to use polarimetry to measure aerosols. In 1996, a series of three French satellite instruments started measuring aerosols with polarized light. Cairns’ technique measures polarization more accurately, integrates more longwave and shortwave polarization information into the mathematical models, and is the first to provide accurate estimates of aerosol size and composition over land.
The RSP instrument views a point in the atmosphere from more than 100 angles, enabling more complete characterization of aerosols by robust mathematical models. RSP and the soon-to-be-launched APS use parallel optical paths to collect measurements from all wavelengths and polarizations simultaneously. This approach to monitoring the continuously changing scene offers greater accuracy compared to previous polarimeters, which used a rotating filter wheel to measure wavelengths and polarizations sequentially.
To test their technique, Cairns and colleagues from Columbia University and the U.S. Department of Energy conducted a series of field campaigns. In 2003, researchers mounted an RSP instrument on a Cessna 310 airplane and flew the instrument above smoke plumes from wildfires in California’s Simi Valley. In 2005, a J31 research aircraft flew RSP over dust plumes in Oklahoma.
In both cases, the airborne data corresponded well with observations from ground-based photometers known to provide accurate aerosol measurements. By integrating the additional polarization wavelengths into their computer models, Cairns estimated that the technique is several times more accurate than previous measurements. The results were presented in January in the Journal of Geophysical Research.
Qingyuan Han, an atmospheric scientist at the University of Alabama Huntsville who was not involved in the study, agreed. “The high sensitivity of polarized reflectance offers tremendous information that could not be obtained by other techniques,” he said.
For instance, Light Detection and Ranging, or lidar, bounces pulses of light off of airborne aerosols and can accurately measure the vertical distribution of aerosols. But current LIDAR systems still struggle to measure aerosol size and composition, says Han, who conducts research using LIDAR. He sees roles for both techniques as a complement to one another.
The techniques developed with the RSP instrument have contributed to the creation of the APS, a spaceborne version that will fly on NASA’s Glory satellite. Functionally identical to RSP, the APS uses slightly different wavelengths of light to improve estimates of ocean color, water vapor, and cirrus clouds. “But the theory for APS and RSP is exactly the same,” said Cairns.
According to Cairns, APS will be especially useful for identifying and quantifying smaller aerosols, which come mainly from human sources. Smaller aerosols are thought to affect climate more than larger aerosols such as dust and salt.
Once Glory launches, scientists expect APS to offer a wealth of new data that will help them peel away long-standing uncertainties about aerosols. “We still don’t understand a lot about them,” Cairns said, “and yet they play such a key role in our climate system.”
> Related release on Glory satellite
> Glory APS Science
> Glory Mission Page