January 17, 2012

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; cblue@aip.org
Catherine Meyers – Writer (301) 209-3088; cmeyers@aip.org
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TOPICS IN THIS ISSUE:

1. A baby crystal is born: Scientists determine the smallest possible cubic lead sulfide cluster that exhibits the same coordination (a key structural property) as bigger bulk crystals.
2. An easier way to remove gallstones: A new patented, ultra-specialized endoscope removes gallstones without the need to remove the gallbladder, too.
3. Flaky graphene makes reliable chemical sensors: Films made of randomly stacked graphene flakes can detect lower concentrations of some chemicals than films made of graphene crystals.   
4. Other content: Upcoming Conferences of Interest; AIP Science Communication Awards: Call for Entries.

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1. A baby crystal is born

Lead sulfide (PbS) forms when an equal number of lead and sulfur atoms exchange electrons and bond together in cubic crystals. Now scientists have determined that a structure comprising 32 lead-sulfur pairs is the smallest possible cubic arrangement that exhibits the same coordination as bulk lead sulfide. (The coordination number is the number of nearest neighbors each atom in the crystal has.) Researchers from McNeese State University in Louisiana, John Hopkins University in Maryland, and the University of Konstanz in Germany identified the “baby crystal” by running computer simulations that calculated the energy and geometry of different structures containing different numbers of atoms. They found that (PbS)32 is the smallest stable unit that possesses both the same cubic structure and coordination number as the bulk crystal. The researchers also experimentally tested their theoretical findings by gently depositing (PbS)32 clusters on a graphite surface where they could easily migrate and merge together to form larger nanoscale structures. By using scanning tunneling microscope images to measure the dimensions of the resultant lead sulfide nano-blocks, the researchers confirmed that the (PbS)32 “baby crystals” had indeed stacked together as theoretically predicted. The results, published in the AIP’s Journal of Chemical Physics, show how small lead sulfide crystals come together to form larger units and could help provide a better understanding of the mechanisms involved in the formation of solids. 

Article: “(PbS)32: A Baby Crystal” is published in the Journal of Chemical Physics.

Authors: B. Kiran (1), Anil K. Kandalam (2), Rameshu Rallabandi, (1) Pratik Koirala (2), Xiang Li (4), Xin Tang (4), Yi Wang (4), Howard Fairbrother (4), Gerd Gantefoer (3), and Kit Bowen (4).
(1) Department of Chemistry, McNeese State University, La.
(2) Department of Physics, McNeese State University, La.
(3) Department of Physics, University of Konstanz, Germany
(4) Depts. Of Chemistry and Material Sciences, John Hopkins University, Md.

2. An easier way to remove gallstones
For more than 100 years, the traditional treatment for the painful growths called gallstones has been removal of the gallbladder, or cholecystectomy. But a new device, patented in China, promises to make removing the entire organ unnecessary. A group of scientists from the Second People’s Hospital of Panyu District and Central South University in China have developed an endoscope specially designed for locating and clearing out gallstones and other gallbladder lesions. The authors describe the device in a paper accepted to the AIP’s Review of Scientific Instruments. A tiny ultrasonic probe at the tip of the endoscope locates gallstones, even small ones embedded in the organ’s lining. Surgeons can use the horn-shaped “absorbing box” to get rid of fine, difficult-to-remove “sludge-like” gallstones – which the authors say can be compared with “sand sprinkled on a carpet” – by sucking them out like a vacuum cleaner. A channel for fluids can inject water into the gallbladder to increase the size of the cavity for ease of performing a surgery, and all the interfaces on the device are standardized, so it can connect to camera systems worldwide. Clinical trials at two hospitals showed “no significant difference” in the surgical safety of the new method compared to another type of endoscope that is often used for cholecystectomies, the authors write. Furthermore, the authors report, the flexibility and reliability of the device was superior to existing devices, and the image quality was better as well. Approximately ten percent of the population suffers from gallstones, hard, pebble-like deposits that can be as small as a grain of sand or as large as a golf ball.

Article: “Design and application of a new series of gallbladder endoscopes that facilitate gallstone removal without gallbladder excision” is accepted for publication in the Review of Scientific Instruments.

Authors: Tie Chiao (1), Wan-Chao Huang, Xiao-Bing Luo, and Yan-De Zhang.
(1) The Second People’s Hospital of Panyu District, China
(2) The National Hepatobiliary and Enteric Surgery Research Center, Central South University, China

3. Flaky graphene makes reliable chemical sensors
Scientists from the University of Illinois at Urbana-Champaign and the company Dioxide Materials have demonstrated that randomly stacked graphene flakes can make an effective chemical sensor. The researchers created the one-atom-thick carbon lattice flakes by placing bulk graphite in a solution and bombarding it with ultrasonic waves that broke off thin sheets. The researchers then filtered the solution to produce a graphene film, composed of a haphazard arrangement of stacked flakes, that they used as the top layer of a chemical sensor. When the graphene was exposed to test chemicals that altered the surface chemistry of the film, the subsequent movement of electrons through the film produced an electrical signal that flagged the presence of the chemical. The researchers experimented by adjusting the volume of the filtered solution to make thicker or thinner films. They found that thin films of randomly stacked graphene could more reliably detect trace amounts of test chemicals than previously designed sensors made from carbon nanotubes or graphene crystals. The results are accepted for publication in the AIP’s journal Applied Physics Letters. The researchers theorize that the improved sensitivity is due to the fact that defects in the carbon-lattice structure near the edge of the graphene flakes allow electrons to easily “hop” through the film.

Article: “Chemical Sensors Based On Randomly Stacked Graphene Flakes” is accepted for publication in Applied Physics Letters.

Authors: Amin Salehi-Khojin (1, 7), David Estrada (2, 3), Kevin Y. Lin (1), Ke Ran (4, 5), Richard T. Haasch (5), Jian-Min Zuo (4, 5), Eric Pop (2, 3, 6), and Richard I. Masel (7).   
(1) Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign
(2) Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign
(3) Micro and Nanotechnology Lab, University of Illinois at Urbana-Champaign
(4) Department of Material Science and Engineering, University of Illinois at Urbana-Champaign
(5) Materials Research Laboratory, University of Illinois at Urbana-Champaign
(6) Beckman Institute, University of Illinois at Urbana-Champaign
(7) Dioxide Materials, Champaign, Ill.

Upcoming Conferences of Interest

• Biophysical Society Annual Meeting: The 56th Annual Meeting of the Biophysical Society will be held Feb. 25 – 29, 2012, in San Diego, Calif.
  http://www.biophysics.org/2012meeting/Main/tabid/2386/Default.aspx
• American Physical Society’s March Meeting: The APS March Meeting will be held Feb. 27 – March 2, 2012, in Boston, Mass.
  http://www.aps.org/meetings/march/
• Optical Fiber Communication Conference and Exposition and the National Fiber Optic Engineers Conference (OFC/NFOEC): The Optical Society’s OFC/NFOEC meeting will be held March 4 – 8, 2012 in Los Angeles, Calif.

http://www.ofcnfoec.org/home/

Physics Today: January Articles
http://www.physicstoday.org

1. Recent developments in U.S. patent law: Legislation making the United States the last country to abandon the first-to-invent patent system should have a significant effect on the way scientists approach patenting.
2. Quantum numbers, Chern classes, and a bodhisattva: A physics Nobel laureate reflects on how he came to understand the significance of a youthful lunchtime encounter with a famous mathematician.
3. Slow slip: A new kind of earthquake: Sandwiched between the shallow region of sudden, infrequent earthquakes and the deeper home to continuous viscous motion lies an intermediate realm of intermittent sliding and rumbling. Discovered in recent years, it still harbors many secrets.

AIP Science Communication Awards: Call for Entries

Entries are requested for the American Institute of Physics’ 2012 Science Communication Awards, which recognize effective science communication, both in print and new media, that improves the general public's appreciation of physics, astronomy, and allied science fields.

Categories: Science Writing (books), Children’s Writing, New Media
Prize: $3,000, an engraved presentation piece, and a certificate
Deadline: February 17, 2012

More information and an entry form are available at http://www.aip.org/aip/writing.

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About AIP
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Charles E. Blue
American Institute of Physics
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