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Argonne scientists can now detect one argon-39 atom per 10 million billion atoms, the equivalent of detecting the atoms from one pint of liquid mixed into Lake Michigan.
To get these results, Argonne physicists had to modify the Argonne Tandem-Linac Accelerator System (ATLAS) ion sources to significantly reduce background contamination from stable, more abundant atomic species so that it could detect accelerated positive argon-39 ions with a 1,000-fold increase in sensitivity, a procedure that has never been accomplished until now.
These superior detection methods will allow scientists to track levels of the radioactive argon-39 isotope in the Earth's ocean circulation. Isotopes -- atoms of the same element with different numbers of neutrons -- such as argon-39 help scientists track the changes in ocean circulation, which is thought to play an important role in climate variations.
Sweden, for instance, has a relatively mild climate for its northern latitude because of the pattern of ocean circulation. Yet at the same latitude, Canada's Baffin Island has a colder and harsher climate.
Argon-39 is created naturally when cosmic rays strike the stable and more naturally abundant argon-40 in the atmosphere. Gaseous argon-39 dissolves into the ocean water when surface waves trap air molecules. In the North Atlantic, the water begins to sink to the bottom of the ocean as it becomes denser due to cooling and an increase in water salinity from evaporation.
Dissolved argon-39 sinks with this water and follows a "conveyor belt" undercurrent that rises again in the Indian and Pacific Oceans. On top of this cold undercurrent is a warm surface current that flows through the East Indies and through the Indian Ocean, where it goes around Africa and up to Europe.
"If this 'conveyor belt' stops, then the warm water that is brought to Europe will stop," said Ernst Rehm (PHY). "We have some idea that this may cause an ice age in Europe."
The phenomenon of global warming could modify the ocean's circulation if water temperatures rise and glaciers release more of their locked-up water into northern oceans, causing a decrease in water salinity and density.
Half the atoms in a sample of argon-39 will decay into potassium-39 in 269 years -- its "half-life." This duration fits the time frame for ocean circulation, since an argon-39 atom created on the surface water of the North Atlantic -- which is subsequently pulled downward by cold, dense water -- will not resurface for another 500 years. By this time, approximately two half-lives have passed and only a quarter of the original argon-39 will remain.
Cosmic rays do not penetrate far into the water to create additional argon-39, and argon does not react with other elements because it is chemically inert. Therefore, determining how much argon-39 is present at various water depths gives scientists an accurate measure of the age of the water samples and an understanding of how fast the water is circulating.
In this experiment, Argonne is collaborating with former Argonne postdoctoral physicist Philippe Collon, who is now at Columbia University's Lamont-Doherty Earth Observatory and is the study's primary investigator, along with other researchers at the Vienna Environmental Research Accelerator in Austria, at Hebrew University in Israel and at the University of Bern in Switzerland.
For the last seven years, the members of the collaboration have refined the methods of accelerator mass spectrometry to obtain a high sensitivity for detecting argon-39.
"It was a challenge for us to develop this technique for very low abundance isotopes," said Rehm.
Previously, if scientists wanted to measure the amount of argon-39 in the ocean at a depth of 5,000 meters accurately, they had to haul up 1,000 liters of water. Today, they only need 20 liters.
Argonne physicists will begin measuring isotopic levels of the laboratory's "elemental homonym" in Atlantic Ocean water samples taken near the South American coast next year.
-- Jeff Evans
Santa Claus will visit Argonne-East Saturday, Dec. 8, for Argonne Club's annual "Breakfast with Santa" holiday party.
Tickets are $2 per child and go on sale on Monday, Nov. 26, in the Building 213 Cafeteria from 11:30 a.m. to 1 p.m. every day through Friday, Nov. 30.
Tickets are good for one of three sessions for visiting with Santa: from 9-11 a.m., 11 a.m. to 1 p.m. and 1-3 p.m.
The Argonne Club board will need new members in 2002.
Officers serve three-year terms and help plan the Argonne Club's activities, like Breakfast with Santa, the Argonne-East employee picnic and group outings.
For more information, contact Stan Reinke (ECT) at ext. 2-6957.
Last summer, then-17-year-old Achintya Madduri became the youngest-ever user of the Advanced Photon Source (APS), one of the world's premier sources of high-energy X-rays for scientific research. That research culminated in a paper published in a top scientific journal and a recent ceremony at Argonne honoring the young scientist.
Madduri achieved this record despite the fact that the ceremony represented his first visit to Argonne. Madduri was a senior at Thomas Jefferson High School for Science and Technology in Alexandria, Va., when he obtained a science internship at the Carnegie Institution in Washington, D.C. He worked with a group of scientists that included Russell J. Hemley of Carnegie's Geophysical Laboratory and the National Science Foundation Center for High Pressure Research. As a part of his internship, Madduri's project involved experiments that required the use of the APS.
"At the time, Achintya was legally too young to set foot in the APS experiment hall," Hemley said. "Using techniques at our laboratory in Washington, he discovered that nitrous oxide transformed unexpectedly into a different form when under high pressure. His work set the stage for the measurements we made at the APS. He prepared the samples for the APS and also analyzed the data."
The APS is the nation's most brilliant source of research X-rays, which are used to illuminate materials and produce high-resolution images of them. Madduri experimented on samples of nitrous oxide (N2O), which under high pressure and temperature transformed unexpectedly into a form known as an ionic solid.
After the senior scientists illuminated the N2O samples with the APS beam, Madduri's analysis of the results was included in the group's paper, "Novel Broken Symmetry Phase from N2O at High Pressures and High Temperatures," published in the journal Physical Review Letters. Madduri received a plaque during the annual APS Users' Meeting at Argonne for his work.
Madduri is now a freshman attending Rice University on full scholarship, and has already been invited to assist with a project researching trace gases in the atmosphere. He is leaning toward a major in engineering.
"Whatever I decide to study, I'm sure the experiences I had at Argonne are going to help me," Madduri said. "So much of physics and engineering overlap these days anyway, and I'll be using a lot of the same research tools and techniques whichever field I go into."
-- Chad Boutin
Argonne-East employees can help students at Chicago's Theodore Roosevelt High School by volunteering a few hours of their time to judge a science fair, help students prepare for college or assist them in building a robot for a national competition.
Roosevelt High School is a large, ethnically diverse public school in Albany Park on Chicago's northwest side.
The high school's annual science fair
will be held Wednesday, Dec. 12, from 8 a.m. to 2 p.m.
Roosevelt's Princeton in Chicago
Schools (PICS) program is thriving at the west-side school, said program director Carolyn West.
PICS is designed to enhance the quality of education and participate in the renewal of public
education in Chicago. PICS students attend Saturday morning tutoring sessions, trips, educational
programs, and receive the help of mentors. The program is a partnership between Princeton
University alumni and the students, parents, faculty, administration and the Albany Park community.
Argonne employees can help by tutoring students or speaking to a class about their careers.
The school's robotics club also wants
help again this year (See the
Dec. 18, 2000 Argonne
News). There are more than 60 students in the school's active robotics club. Students range from
freshmen to seniors, who will all work on one robot per year for the national contest. Teaming up
with engineers from businesses, universities and Argonne, students brainstorm, design, construct
and test a robot to compete in a spirited, no-holds-barred tournament complete with referees and
time clocks.
Donations of soccer equipment,
including balls and goals, are needed for the YouthNet after-school program at Roosevelt.
For more information on volunteering or donating equipment, call Carolyn West at (773) 456-6162.
Energy Daily is now available to employees via the Argonne Information Management System.
Five days a week, Energy Daily presents current information on energy-related developments taking place on Capitol Hill, the White House, within the U.S. Department of Energy and elsewhere in the world.
Argonne purchased a one-year site-wide subscription to this publication for the use of employees only.
Access is available at www.aim.anl.gov. To locate Energy Daily, click on the "new subscription" message or search on the title in the library catalog at www.aim.anl.gov/alec/index.html or the library list of e-journals at www.aim.anl. gov/ejournal/.
2001 W-2 and Earnings Summaries will be mailed to employees' homes in January 2002. To prepare for the distribution of the W-2's, each employee should verify the accuracy of the information that currently appears on his or her check stub, including name, address and Social Security number.
Send corrections to the Payroll Department as soon as possible, but no later than Wednesday, Dec. 12, 2001 to avoid W-2 errors and delivery delays.
Division Human Resources representatives should also be notified of address changes. HR representatives' names and telephone numbers are listed on page 6-9 of the Argonne telephone directory and on the HR Web site.
Employees can develop insights and skills to effectively manage large and small projects in a class to be offered at Argonne-East in mid-January.
"Successful Project Management" (HR 241) will be presented Thursday and Friday, Jan. 17-18, 2002. Registration deadline is Monday, Dec. 3, 2001.
Participants will learn how to define, plan and assign work; obtain meaningful commitments; manage risk; monitor and evaluate results and correct mistakes within approved budgets and schedules.
The seminar will be presented by Arnold Ruskin in cooperation with the California Institute of Technology Industrial Relations Center. Ruskin held senior management positions at the Jet Propulsion Laboratory and served as adjunct professor of engineering and director of the engineering executive program at UCLA. He is the author of two books and numerous articles.
The cost is $825 per person. To enroll, contact a Training Management System representative. For more information, call Charlyne Robinson (HR) at ext. 2-3410.
Sodexho will hold a holiday book sale in Argonne-East's Building 213 Cafeteria Wednesday, Nov. 28, from 11 a.m. to 2:30 p.m.
Books, games and toys will be sold for 30-70 percent less than retail price. Cash, checks and credit cards will be accepted.
Electronics and Computing Technologies will offer several classes at Argonne-East in December.
Unless otherwise specified, classes will be held in Building 221, Room A142 and are limited to 10 participants. Full class descriptions, schedules and enrollment forms are available online. For more information about enrollment procedures, contact Diane Cavazos at ext. 2-7153 or dkcavazos@anl.gov.
Beginning Unix (ECT564) -- This class
consists of two three-hour sessions for a total of six hours. First session: Tuesday, Dec. 4, 9
a.m. - noon. Second session: Thursday, Dec. 6, 9 a.m- noon. Cost: $265.
vi Editor in Unix (ECT567) -- Friday,
Dec. 7, 9 a.m. - noon. Cost: $180.
Advanced Excel 2000 (ECT379) --
Tuesday, Dec. 11, 8:30 a.m. _ 4:30 p.m. Cost: $215.
Advanced Word 2000 (ECT378) -- Monday,
Dec. 10, 8:30 a.m. - 4:30 p.m. Cost: $215.
Advanced Access 2000 (ECT380) --
Wednesday, Dec. 12, 8:30 a.m. - 4:30 p.m. Cost: $215. Class size limited to eight.
Front Page 2000 (ECT383) -- This class
is two full days. Thursday, Dec. 13, and Friday, Dec. 14, 8:30 a.m. - 4:30 p.m. Class
size limited to eight. Cost: $430.