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X-ray
imaging current-driven magnetic
domain-wall motion in nanowires
The quest to increase both computer
data-storage density and the speed at which one can read
and write the information remains unconsummated. One novel
concept is based on the use of a local electric current to
push magnetic domain walls along a thin nanowire. A German,
Korean, Berkeley Lab team has used the x-ray microscope XM-1
at the ALS to demonstrate that magnetic domain walls in curved
permalloy nanowires can be moved at high speed by injecting
nanosecond pulses of spin-polarized currents into the wires,
but the motion is largely stochastic. This result will have
an impact on the current development of magnetic storage
devices in which data is moved electronically rather than
mechanically as in computer disk drives. Full
story.
Publication about this research: G.
Meier, M. Bolte, R. Eiselt, B. Krüger, D.-H. Kim, and
P. Fischer, "Direct imaging of stochastic domain-wall
motion driven by nanosecond current pulses," Phys.
Rev. Lett. 98, 187202 (2007).
Contact: Peter Fischer, pjfischer@lbl.gov
Extracellular
proteins promote
zinc sulfide aggregation
Researchers from the ALS, Berkeley Lab's
National Center for Electron Microscopy (NCEM), and Lawrence
Livermore National Laboratory analyzed biofilm samples rich
in zinc sulfide and dominated by sulfate-reducing bacteria,
which were collected from lead–zinc mine waters. The
researchers were curious about the relationship of the organic
material and metals, particularly how organics affect mobility,
and its potential for bioremediation. It is known that some
organics promote aggregation. Amine-bearing molecules, for
example, can organize sulfide nanoparticles into semiconductor
nanowires. The research team used a series of imaging techniques
and detectors to analyze aggregates of biogenic zinc sulfide
nanocrystals in the biofilms. Their examination yielded excellent
results and some surprises. They were able to prove that
natural organic matter promotes dense aggregation of the
zinc sulfide nanocrystals into much larger spheroids and
that the organic matter is preserved in nanometer-scale pores
in the spheroids. What was not expected was the presence
of proteins in the spheroids, making them a key component
in aggregation and an example of extracellular biomineralization. Full
story.
Publication about this research: J.W.
Moreau, P.K. Weber, M.C. Martin, B. Gilbert, I.D. Hutcheon,
and J.F. Banfield, "Extracellular proteins limit the
dispersal of biogenic nanoparticles," Science 316, 1600
(2007).
Contact: John Moreau, jwmoreau@usgs.gov
Upgrades to
Beamlines 8.2.1 and 8.2.2
The ALS is midway through a two-year
upgrade to Beamlines
8.2.1 and 8.2.2,
the two superbend macromolecular crystallography beamlines
operated by the Berkeley Center for Structural Biology (BCSB).
The improvements are designed to allow screening of, and
data collection from, small crystals and will help resolve
structures of large complexes.
Two major parts of the upgrade have
been completed. In December 2006, an upgraded large-format
CCD detector was installed on Beamline 8.2.1 to facilitate
high-resolution data collection and the study of crystals
with large unit cells. After extensive offline testing, a
Rigaku ACTOR robot was installed in the endstation hutch
at Beamline 8.2.2 during the recent shutdown. It is compatible
with other automounters at the ALS and has a Java control
system that has been integrated into the BCSB BOS beamline
control software. An identical robot will be
installed at Beamline 8.2.1 and is presently undergoing
offline testing. Remote-viewing and data-collection software
are also under development.
The Rigaku ACTOR robot was extensively
tested offline to assure safety to users (large envelope
of motion, key-activated dead man's switch), safety to equipment
(detector, shutter, etc.), hardware interlocks (doors, dewar
lid), software interlocks (beamstop, detector cover), and
exclusion zones.
Later this year, a new MD2 microdiffractometer from Accel
will be installed on Beamline 8.2.1. The MD2 is designed
for working with small crystals; it is capable of high-resolution
crystal imaging, and the integrated beam collimation devices
will define the beam of a desired size with minimized air
scatter.
Next year will be devoted to upgrading
the optics on Beamline 8.2.1, which will extend
its capacity to the limits of the technology, with the goal
of decreasing the spot size from 100 to 30 microns and increasing
the beam brightness by a factor of 5. An internally cooled
Si design was chosen for the front-end parabolic mirror as
it gives the best thermal performance of the options available.
The second mirror will be replaced with one of the same design
as is currently used, but with a lower slope error. The monochromator
upgrade will include the addition of multilayer crystals,
which will give the option of higher flux at lower resolution
(similar to the existing monochromator on 12.3.1), and direct
liquid-nitrogen cooling of crystals, which will reduce thermal
distortions by more than a factor of ten.
These beamlines have grown tremendously since their commissioning
in 2003, becoming two of the most productive crystallography
beamlines at national synchrotron light sources. This upgrade,
which is funded by the Howard Hughes Medical Institute, will
ensure that they continue at their high level of operation.
Contact: Paul Adams, pdadams@lbl.gov
Groundbreaking
ceremonies for
User Support Building and Guest House
This year's ALS Users' Meeting
will feature two official Laboratory groundbreaking ceremonies
in two days, unprecedented in the history of Berkeley Lab.
All ALS and Laboratory staff are invited.
On Thursday, October
4, at 12:15 p.m., the groundbreaking ceremony for the ALS
User Support Building will take place on the Renner Deck
next to the building site west of the ALS. The 30,000-square-foot,
three-story structure, to be funded by DOE's Office of Basic
Energy Sciences, will offer modern experimental staging and
assembly space, support laboratories, and offices.
ALS User Support Building.
The next day, the Laboratory will
host the groundbreaking ceremony for the Berkeley Lab Guest
House (12:00 noon on the site of the new structure, west
of Building 2). Located
within a short walk of the ALS and the cafeteria, the Guest
House will provide 70 beds in single- and double-occupancy
rooms and will include a main lobby, lounge areas, a fitness
center, laundry, vending areas, and an outdoor patio. Funding
for the Guest House will be provided through external financing,
and expenses will be covered by revenues collected for room
rentals, vending, and sales. The Howard Hughes Medical Institute
has provided a generous grant for furniture, fixtures, and
equipment.
Berkeley Lab Guest House.
The late Gary Krebs, ALS User
Services Group Leader from 1998 to 2007, worked tirelessly
on plans for the Guest House. Members
of his family are among those expected to attend.
Contact: Jeff Troutman, jptroutman@lbl.gov
UEC Corner:
ALS Users' Meeting update
by Tony van Buuren
 For
the first time, the Users' Meetings
of the Advanced Light Source and the Molecular Foundry
are being organized jointly and simultaneously. The meeting
will be held on October 4–6. At the meeting there will
be a joint plenary session, a joint poster session, and
several joint workshops. We hope to stimulate strong interactions
between the two user communities. The ALS meeting co-chairs,
Peter Fischer and Ken Goldberg, together with Jeff Bokor
from the Molecular Foundry, have put together an exciting
program highlighting scientific achievements at these facilities
and looking toward the future. More information on the
Users' Meeting can be found on the Web
site.
Also, it is time for the annual election
of new members to the ALS Users' Executive Committee. Please
take a moment to look at the UEC
Election Web site and nominate suitable candidates
from the ALS community who would be willing to serve. If
you have any questions, please contact me or any other UEC
representative. I look forward to meeting many of you at
this year's meeting.
Contact: Tony van Buuren, vanbuuren1@llnl.gov
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