Dennis Nordlund working at SSRL's Beamline 5-2.
How Cagey Electrons Keep Hydrated
Water, despite its essential role in nature, remains a deeply mysterious substance. A long list of water's unusual properties tantalizes researchers even today, and scientists at the Stanford Synchrotron Radiation Laboratory (SSRL) and around the world are using x-rays to help address these questions. Working with SSRL scientist Anders Nilsson, researcher Dennis Nordlund and colleagues are turning up new clues, and their
latest results are published in a recent issue of Physical Review Letters.
"Hydrated electrons" have been well-studied since the 1960s, and occur when free electrons become dissolved in water. Each water molecule is made up of two hydrogen atoms bound to an oxygen atom, and hydrated electrons form when a handful of water molecules congregate around a free electron, essentially trapping it in a cage of molecules. Most agree that these cages consist of about six molecules. But the dynamics behind the process—how neighboring water molecules swing around, pointing one hydrogen atom inward to trap the electron—is not well understood.
Nordlund and colleagues, gathering data at Berkeley's Advanced Light Source and at MAX-Lab in Sweden, have for the first time measured how long an electron, having encountered a hydrogen atom of one water molecule, can stay in one place without hopping away, allowing other water molecules to swing into place and trap it.
Master of Flow
Martin Lee has spent his entire career thinking about energy—whether it be the flow of electrons, or the flow of "chi."
Fresh out of New York University’s masters program, and well before SLAC became SLAC, Lee left Bell Labs in 1962 to work on Stanford's new—and as yet unbuilt—linear electron accelerator.
"I interviewed with Greg Loew," said Lee. "He drove me up here, I saw cows munching on grass, and he said, 'So, you want to work here?'"
Lee says his first and most memorable project at SLAC involved the beam alignment system. "This one struck my fancy because it really marked a time for me, personally and historically."
Keeping the linac properly aligned to within thousandths of an inch over its two-mile length required technology that, until then, was unheard of. Without the aid of computers, Lee tackled the problem by designing a system of lenses that would focus a laser beam at one end of the linac into a test pattern at the other end. The challenge resided in customizing each lens, one for each 40-foot section of linac. All told, the linac uses almost 300 of these "Fresnel" lenses.
"It had taken me months to design the first lens," he said. "We rented an abandoned railroad tunnel in South San Francisco to test the system, and it worked. Then they said, 'Martin, design 300 more!'"
By this time, the Stanford Computation Center had gotten its first, building-sized computer for non-business users. Lee learned to write code to expedite the design of the remaining 300 lenses.
That project inspired him to pursue his PhD, he says, because the minutia of engineering left him no time for thinking. Since then, Lee has worked on nearly every major project at SLAC. Although he officially retired from SLAC in 2004, he was rehired in June 2007 and says the only thing that changed was his office number. Now, he consults with various groups, and calls himself the "Ambassador of Technology Transfer."
When not at SLAC, perhaps Lee's truest passion is tai chi, a type of slow-motion Chinese martial art practiced with the aim of promoting health and longevity. Lee has taught tai chi for 35 years, and has written two best-selling books on the subject with the help of his daughters—Melinda, who currently works
in the SLAC communications office; and Joyce, who spent two summers working for SLAC's travel office when she was in high school.
Although he still teaches to this day, don't look for him on land—he and his family now teach tai chi on the high seas, aboard cruise ships operated by Crystal Cruises. Having done more than 30 such cruises, their most recent jaunt lasted 80 days and—fittingly—took them around the world.
Asked about what he likes most about cruises, he says it gives him a lot of time to think and reflect. "I actually do a lot of writing both on my work and tai chi. I wrote my most recent paper on the last cruise," he says. "On cruises, that's where my two worlds connect."
Come Revel at Today's SLAC Holiday Party
The annual SLAC Holiday Party begins today at 11:00 a.m. Come join the celebration and enjoy a buffet lunch, the movie The Polar Express and continuous raffle drawings. It all takes place in the Panofsky Auditorium and the Linear Cafe today between 11:00 a.m. and 1:00 p.m.
More information is available at the
holiday party webpage.
Since early Monday, December 17, equipment in the computer center has been suffering from stability problems that appear to be caused by "dirty" power. The likely cause is a combination of the PEP II startup and limited transformer capacity in the SLAC master substation while work continues to upgrade one of the two transformers feeding the site. The limited transformer capacity causes harmonics and spikes generated by the PEP II power supplies to give rise to an unusually high level of harmonics and spikes across the site.
Computing equipment is generally less tolerant of harmonics and spikes than lights, motors, space heaters, etc. A small fraction of equipment in the computer center is refusing to work at all, and a larger fraction appears to be unstable. We
apologize for adding to the instability on Tuesday by tripping a breaker while investigating the source of the instabilities.
We expect computer center services to be unstable until the late this week or early next week when the second master substation transformer will be back in service. Staff will be on call to monitor the infrastructure and restore critical services that fail. Because of reduced staffing during the holidays, failures and trouble calls will be prioritized and responded to with the available manpower, in consultation with
laboratory and collaboration managers.
Thank you for your understanding.
of the Week
Battery-operated toys aren't just for kids anymore. If holiday shopping lists include battery-powered items, consider buying rechargeable batteries and a small battery charger to go along with them. Properly used, a rechargeable NiMH AA battery will outlast hundreds of disposables. Be sure to recycle your batteries when they reach the end of their useful life. A solar charger can make a nice gift too, and reduce energy costs.
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