Previous Editions____________________________________________________________________________SSRL Headlines Vol. 11, No. 2 August, 2010____________________________________________________________________________
Contents of this Issue:
1.
Prof. Chi-Chang Kao Named Associate Laboratory Director for SSRL
"We've not only recruited an outstanding individual in management and
leadership, but also a person who really excels in x-ray science and
techniques," said Keith Hodgson, Associate Laboratory Director for Photon
Science. "[In his previous post] as Chairperson of Brookhaven National
Laboratory's National Synchrotron Light Source, Chi-Chang demonstrated that he
can undertake his new role very effectively. He's also an extremely
accomplished physicist in the area of x-ray physics and scattering. Both of
these elements-strong leadership skills and scientific research expertise will
serve him well at SLAC." Read more at: http://today.slac.stanford.edu/feature/2010/ssrl-kao.asp
A group of scientists at Stanford University, including graduate student
Jonathan Rivnay and Prof. Alberto Salleo, working with SSRL staff scientist
Mike Toney and Antonio Facchetti from Polyera Corp., investigated the structure
and properties of an n-type semiconducting polymer thin film using SSRL Beam
Lines 11-3, 7-2, and 2-1. They found that the polymer molecules, previously
thought to be disordered, packed in a
face-on manner with the pi-bonds mostly perpendicular to the film, unlike the
p-type semiconducting materials.
This structure is unexpected, since a molecular arrangement with the
pi-stacking along the film surface (usually found in p-type polymers) was
thought to be critical for conducting charges. The researchers hypothesize that
extensive interconnectivity in the polymer structure allows multiple pathways
for electrons to travel through the material. These results highlight the
importance of understanding how structure influences function in semiconducting
organics. This work was published on the Advanced Materials website on
July 9, 2010.
To learn more about this research see the full scientific highlight
Taken together, both steps bring the unique material closer to use in the
nascent technology of spintronics, with the potential to result in, among other
advances, smaller, more efficient transistors and memory devices. Both steps
could also give physicists from fields as varied as condensed matter physics,
cosmology, and particle physics glimpses into such exotic phenomena as magnetic
monopoles, the fractional quantum Hall effect and axion fields, for starters.
As explained in a paper in Science, in step 1, Chen and his
collaborators took the marvelous property of a three-dimensional topological
insulator-in which electrons flow inexorably along the surface in the same
direction, slaloming around defects instead of scattering off them in all
directions-and broke it.
In step 2, the team demonstrated the ability to "tune" the topological
insulator's Fermi energy level, the amount of energy in the most energetic
electrons still occupying a specific quantum state.
Essentially, the team completely redrew the energy portrait for the topological
insulator. Initially the portrait showed two cones, called Dirac cones, with
their apexes touching at the so-called Dirac point, where electrons can cruise
serenely along the insulator's surface. Introducing magnetic impurities into
the system turns electrons into bumbling pedestrians that scatter and bounce
off the impurities, in effect creating a gap separating the upper and lower
Dirac cones. While tuned into that gap, the usually free flow of electrons
across the material's surface remains "broken." Read more at: http://today.slac.stanford.edu/feature/2010/dirac-gap.asp
To learn more about this research see the full scientific highlight
Unlike photovoltaic technology currently used in solar panels-which becomes
less efficient as the temperature rises-the new process excels at higher
temperatures.
Called "photon enhanced thermionic emission," or PETE, the process promises to
surpass the efficiency of existing photovoltaic and thermal conversion
technologies.
"This is really a conceptual breakthrough, a new energy conversion process, not
just a new material or a slightly different tweak," said Nick Melosh of the
Stanford Institute for Materials and Energy Science, a joint institute of the
Department of Energy's SLAC National Accelerator Laboratory and Stanford
University. Melosh led the research group. "It is actually something
fundamentally different about how you can harvest energy." And the materials
needed to build a device to make the process work are cheap and easily
available, meaning the power that comes from it will be affordable. Melosh is
senior author of a paper describing the tests the researchers conducted. It was
published August 1 in Nature Materials.
"Just demonstrating that the process worked was a big deal," Melosh said. "And
we showed this physical mechanism does exist, it works as advertised." Critical
to the team's efforts to demonstrate PETE was time spent at the Stanford
Synchrotron Radiation Lightsource, said Jared Schwede, lead author of the paper
and a graduate student working with Melosh. "It's that experimental
infrastructure at SLAC that made some of our experiments possible," Schwede
said, along with his colleagues' expertise. Read more at: http://news.stanford.edu/news/2010/august/new-solar-method-080210.html
See also: http://www.stanforddaily.com/2010/08/12/pete-could-improve-solar-tech/
"It has been one of the greatest pleasures of my job to get to know Piero over
the last year," said SLAC Director Persis Drell. "He's been a great leader for
SSRL, and is a very respected voice in the laboratory community. Piero has
managed major transitions at SSRL and has really been leading the light source
to the future."
Drell continued: "We are also here to celebrate and welcome Chi-Chang as our
new Associate Laboratory Director for SSRL. In my first conversation with
Chi-Chang [two years ago], I had a very strong feeling that this guy belongs at
SLAC. He brings a breadth of vision and experience. He's a strong voice for
SSRL and future of photon science more broadly. I am confident that Chi-Chang
will lead us and SSRL to the future." Read more at: http://today.slac.stanford.edu/a/2010/08-30.htm
"The LCLS shows what the scientific workforce of our nation, in cooperation
with our international partners, is capable of achieving," said Secretary Chu.
"Pioneering research will remain critical if the U.S. is to stay a global
leader when it comes to innovation and competitiveness."
Stanford University President John Hennessy spoke alongside Secretary Chu and
other guests, including U.S. representatives Zoe Lofgren (D-San Jose) and Mike
Honda (D-San Jose). "I'm struck by the many accomplishments of SLAC and the
many ways the researchers here exemplify the pioneering tradition for which
Stanford is known," Hennessy said. "For almost half a century, SLAC has been
adventurous in its thinking, boldly launching new efforts in its search for
knowledge. We're privileged to have this world-class research facility here at
our university."
SLAC Director Persis Drell said, "We at SLAC could not have delivered the LCLS
on our own; the Department of Energy, Stanford University and all our partners
were always there when we needed them. And now we have a facility that is
annihilating expectations. The early experiments are swimming in data and are
already exploring new frontiers-the science is starting to flow."
Read more at: http://home.slac.stanford.edu/pressreleases/2010/20100816.htm
See also: http://today.slac.stanford.edu/feature/2010/lcls-dedication.asp
"I'm very happy," said Lee. "It feels very nice to be recognized for my work."
The award, which is open to senior graduate students and those seven or fewer
years into their professional scientific careers, will be presented on October
18 at the SSRL/Linac Coherent Light Source Users' Meeting. In turn, Lee will
give a short presentation describing his recent research.
Until last month, Lee worked as a postdoc in the laboratory of Erica Ollmann
Saphire at the Scripps Research Institute. There, he studied the Ebolavirus,
which causes an untreatable disease that kills 50 to 90 percent of people who
contract it. Using SSRL and other U.S. synchrotrons, Lee was able to uncover
the structure of the Ebolavirus glycoprotein, which initiates the attachment
and fusion of the virus and the host membranes, when it was bound to an
antibody from a human survivor of the virus.
The work was especially challenging because glycoproteins are very difficult to
crystallize. As a result, Lee and his colleagues needed to make over 140
different protein variants and grow over 50,000 crystals before finding one
that would diffract the synchrotron light well enough to create images. But
once they did, they were able to reveal the protein's structure, offering
insight into why antibodies for the virus are so rare and into the very few
sites to which an antibody can bind. This provides templates for the future
development of immunotherapeutics and vaccines that may work against the virus.
(More about this research can be found in the SSRL Highlight linked below.)
Read more at: http://today.slac.stanford.edu/feature/2010/spicer.asp
Plan to participate in the Annual SSRL/LCLS Users' Meeting and Workshops,
October 17-21, 2010 to learn about the latest plans, new developments and
exciting user research at LCLS and SSRL. It is also a great time to interact
with other scientists, potential colleagues, and vendors of light
source-related products and services.
The event kicks off on October 17 with workshops focused on LCLS Data Analysis
and LCLS II. LCLS/SSRL 2010 officially begins on October 18 with a joint
plenary session featuring updates from SLAC and DOE, a keynote talk by Jens
Norskov on "Converting Sunlight into Fuels - the Role of Interface Catalysis,"
science highlights from SSRL and LCLS, and a user science poster session. The
Spicer Young Investigator Award, Klein Professional Development Award, Lytle
Award, and the Outstanding Student Poster Session Awards will be presented on
this day.
Separate sessions focusing on SSRL and LCLS facility development,
instrumentation, and user science will be held concurrently on October 19,
followed by meetings of the respective SSRL and LCLS Users' Organizations.
A number of concurrent workshops will be held on Wednesday, October 20,
including Frontier Biology and Imaging with XFEL; Challenges in Imaging
Processing in Tomographic Data Sets; High Energy Density Science; AMO
Instrumentation and Science Opportunities; SXR Instrumentation and Science
Opportunities; and Developing Strategies, Preparing and Getting the Most from
Macromolecular Crystallography Experiments.
SSRL BEAM TIME REQUEST DEADLINES.
Proposal spokespersons or their authorized
lead contacts can submit new beam time requests for the first scheduling period
in our 2011 experimental run (mid November 2010 - February 2011) by September
1. Requests for time on Macromolecular Crystallography (PX) time are due
September 15. Request beam time via the user portal.
SUBMIT NEW SSRL PROPOSALS BY SEPTEMBER 1 (X-ray/VUV) OR DECEMBER 1
(PX/X-ray/VUV).
New proposals can be submitted 3 times a year: June 1,
September 1, and December 1 for X-ray/VUV and April 1, July 1, and December 1
for Macromolecular Crystallography (PX). X-ray/VUV proposals submitted by
September 1 will be peer reviewed, rated and eligible for beam time beginning
in February 2011. Both X-ray/VUV and PX proposals should be submitted via the
user portal.
See our 2011 Operating Schedule.
The workshop focused on a technique called low-energy x-ray absorption
spectroscopy. When conducting XAS, a researcher aims an x-ray beam at a sample
and tunes the beam through a range of energies. Specific chemical elements
absorb specific energies, so when just the right energy beam hits the sample,
atoms of a particular element will eject electrons, providing information about
the atom's electronic structure. In particular, the workshop covered low-energy
ranges (from 2.4 to 4 keV) and the element sulfur, a technique called "S
K-XAS."
With applications in biology, chemistry, and environmental and materials
science, S K-XAS and x-ray fluorescence imaging can be used to probe
metal-sulfur bonds that make certain human proteins function, image where
sulfur accumulates in a plant grown in sulfur-contaminated soil, and reveal the
different forms of sulfur present in a soil sample, to name a few examples.
Read more at: http://today.slac.stanford.edu/feature/2010/ssrl-summer-school.asp
__________________________________________________________________________
SSRL Headlines is published electronically monthly to inform SSRL users,
sponsors and other interested people about happenings at SSRL. SSRL is a
national synchrotron user facility operated by Stanford University for the
U.S. Department of Energy Office of Basic Energy
Sciences. Additional support for
the structural biology program is provided by
the DOE
Office of Biological and Environmental Research, the NIH
National Center for Research Resources and the NIH Institute for General Medical
Sciences. Additional information about
SSRL and its operation and schedules is available from the SSRL WWW
site.
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