AIP Physics News Highlights: Oct. 24

Newswise — Physics News Highlights of the American Institute of Physics (AIP) contains summaries of interesting research from the AIP journals, notices of upcoming meetings, and other information from the AIP Member Societies. Copies of papers are available to journalists upon request.

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Charles Blue – Manager (301) 209-3091; [email protected] Meyers – Writer (301) 209-3088; [email protected]Jennifer Lauren Lee – Writer (301) 209-3099; [email protected]

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TOPICS IN THIS ISSUE:

1. On the nanoscale, particles flow in unexpected ways: Whether it’s water through the English Channel or a river channel, we assume fluids flow in predictable ways. But by zooming in on nanoscale channels, researchers discovered that fluids behave in a rather different, sometimes even counterintuitive, way.2. For diabetics, spectroscopy may replace painful pinpricks: Researchers at the Massachusetts Institute of Technology have taken a key step toward developing a portable device to test diabetics' blood glucose by shining a light through their skin. 3. Nanotechnology to the rescue: Biosensing tool to detect salmonella holds promise for preventing common food poisoning: Food poisoning from salmonella bacteria is a worldwide public health hazard. Carbon nanotubes combined with immune system molecules have yielded a highly sensitive and specific biosensor surveillance tool that may one day help prevent these dangerous outbreaks. _______________________________________________________ 1. On the nanoscale, particles flow in unexpected ways

Researchers studying how fluids travel through nanoscale channels were surprised to discover that the fluids don’t flow equally well in all directions. Contrary to the behavior in the macroscale world, the researchers discovered that methyl alcohol, when it was placed in a network of nanoscale channels in a mineral known as a zeolite, diffused 1,000 times faster in one direction than another. This is the first known evidence of such highly unequal diffusion of molecules in a nanoporous material. This highly lopsided flow occurred despite the fact that the diameters of the respective channels are quite similar. In the mineral, two types of nanoscale channels are present: 8-ring and 10-ring channels. The numbers refers to the relative size of the pores in the material, though they are extremely close in size with only subtle differences in geometry. The methyl alcohol molecules were stored initially inside an optical cell. At the beginning of the experiment, the pressure in the surrounding atmosphere is increased instantaneously and kept constant for the rest of the experiment. The methanol molecules then enter the zeolite voluntarily since they naturally prefer to be in the zeolite than in the gas phase. Once inside the mineral, the researchers measured the particle concentration at various points along the pores. From these profiles, they were able to calculate the particle flux (number of particles that cross a certain area in a certain time) and observed the highly biased flow. Earlier research reported that the diffusivity of a guest molecule inside a pore network is extremely sensitive to the ratio of the pore window and molecule diameter, particularly if both quantities are close to each other, as was the case with the zeolite channels and the methyl alcohol atoms. The researchers in this study speculate that since the 8-ring window is slightly smaller than the 10-ring window, a smaller diffusivity (and therefore a smaller flux) might be expected. Another reason might be the different pore geometry (straight in the case of the 10-ring channels versus windows and cavities in the 8-ring channels). Presented in the AIP’s Journal of Chemical Physics, this apparently counterintuitive discovery has far-reaching implications for the understanding, development, and exploitation of novel microscopic materials, including nanotubes and “intelligent” cell membranes for purposeful drug delivery, the functionality of which is based on an extreme direction dependence of molecular mobilities.

Article: “Micro-imaging of transient guest profiles in nano-channels” is accepted for publication in the Journal of Chemical Physics.

Authors: F. Hibbe (1), V.R.R. Marthala (2), C. Chmelik (1), J. Weitkamp (2), and J. Kärger (1).

(1) Faculty of Physics and Earth Sciences, University of Leipzig, Germany(2) Institute of Chemical Technology, University of Stuttgart, Germany

2. For diabetics, spectroscopy may replace painful pinpricks

Part of managing diabetes involves piercing a finger several times daily to monitor blood sugar levels. Raman spectroscopy could let diabetics monitor glucose without those daily pinpricks. In the past, this would have required a tabletop's worth of equipment. Two former graduate students at MIT's George R. Harrison Spectroscopy Laboratory, Chae-Ryon Kong and Ishan Barman, detail in the AIP’s journal AIP Advances how to potentially reduce the overall size of this sensor by making an important part of this equipment smaller. Their Raman spectrograph works by shining a low-powered laser though the thin fold of skin between the thumb and forefinger. As the laser's photons move through the skin, they strike the vibrating molecules around them. A portion of these photons interact with the vibrating molecules in ways that change their energy levels. This is called Raman scattering. Each type of molecule produces a unique set of energy levels that show up as a spectrum and identify the molecule. Unfortunately, less than one out of one million photons undergoes Raman scattering. So it is important to capture as many scattered photons as possible, then filter out everything but the Raman photons. Optical filters can do this, but they are only effective when the photons hit them within a narrow range of angles. Previous researchers have used a compound parabolic concentrator (CPC) for this purpose, yet it takes a very large CPC to achieve the high degree of collimation needed. Kong and Barman turned to a more compact mirror, a compound hyperbolic concentrator (CHC), which uses a lens to focus light into the necessary tight beam. "The new design is from five to 20 times smaller than if we used a CPC to achieve the same performance," Kong said. This development is the first step toward making portable Raman spectroscopy possible. According to Ramachandra Dasari, the lab's associate director, such portable Raman spectrographs could also be used to identify other blood chemical markers of disease, and to determine if biopsies contain cancerous tissue. The corresponding tests would take about one minute. The current prototype is the size of a shopping cart. "Our next step is to miniaturize this and make it portable," he said. Dasari expects to build a portable prototype over the next couple of years.

Article: “A novel non-imaging optics based Raman spectroscopy device for transdermal blood analyte measurement” is accepted for publication in AIP Advances.

Authors: Chae-Ryon Kong (1), Ishan Barman (1), Narahara Chari Dingari (1), Jeon Woong Kang (1), Luis Galindo (1), Ramachandra R. Dasari (1), and Michael S. Feld (1).

(1) George R. Harrison Spectroscopy Laboratory, Massachusetts Institute of Technology

3. Nanotechnology to the rescue: Biosensing tool to detect salmonella holds promise for preventing common food poisoning

Pick your poison from this smorgasbord of recent salmonella outbreaks in the United States: ground turkey; fresh papayas; alfalfa sprouts. That’s in 2011 alone, and the list goes on, according to the U.S. Centers for Disease Control and Prevention. But perhaps not for long, thanks to a promising new biosensor nanotechnology that could identify the presence of salmonella bacteria before contaminated food or animals reach the marketplace. In the AIP’s journal AIP Advances, research collaborators from the University of Pennsylvania and Alabama State University report encouraging early results toward the development of just such a tool. “The key aspect of our work is that we detect salmonella in a medium that closely resembles the complexity of the real-world applications for food safety surveillance,’’ explains Penn’s A.T. Charlie Johnson, Ph.D. Carbon nanotubes are novel materials known for their unique atomic architecture. This endows them with remarkable electrical, mechanical, and physical properties. When combined with biological molecules, such as antibodies, carbon nanotubes have the potential to perform a range of new and useful functions in miniature biotechnology devices – from detecting breast cancer cells to the Penn-Alabama State team’s salmonella project. "The large surface area of carbon nanotubes makes them very sensitive detectors. By combining that with the chemical specificity of antibodies for salmonella, we hope to create a device to protect the public health," explains Johnson. Further research is needed before a carbon nanotube biosensor for salmonella is available commercially. But these results help bring the concept a step closer to reality – and to controlling food poisoning outbreaks.

Article: “A carbon nanotube immunosensor for Salmonella” is published in AIP Advances.

Authors: Mitchell B. Lerner (1), Brett R. Goldsmith (1), Ronald McMillon (2), Jennifer Dailey (1), Shreekumar Pillai (2), Shree R. Singh (2) and A. T. Charlie Johnson Jr. (1).

(1) University of Pennsylvania (2) Alabama State University________________________________________________________

Upcoming Conferences of Interest

- AVS Symposium: The AVS 58th International Symposium and Exhibition will be held October 30 - November 4, 2011, at the Nashville Convention Center, in Nashville, Tenn.http://www2.avs.org/symposium/AVS58/pages/greetings.html- ASA Meeting: The 162nd meeting of the Acoustical Society of America will be held October 31 - November 4, 2011, in San Diego, Calif.http://www.acousticalsociety.org- APS/DFD Meeting: The American Physical Society/Division of Fluid Dynamics meeting will be held November 20 - 22, 2011, in Baltimore, Md.http://www.aps.org/units/dfd/meetings/meeting.cfm?name=DFD11

Physics Today: November Articleshttp://www.physicstoday.org

1. Roaming reactions: The third way: Chemists have long held that there are two ways in which a molecule can break apart. But recent results show a third possibility, and its discovery may have far-reaching implications.2. Watery Enceladus: In 1980, telescopes revealed that one of Saturn’s rings is centered at the orbit of Enceladus, a medium-sized Saturnian moon. It was the first hint that Enceladus is a world like no other.3. Problems with problem sets: Undergraduate physics problem sets and textbook examples often assume prior knowledge that is more common in men than in women. Could that difference be deterring women from pursuing careers in physics?

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