| July
26, 2005
[NIST
Tech Beat Search] [Credits] [NIST Tech Beat
Archives] [Media
Contacts] [Subscription Information]
Researchers
Help Sort Out the Carbon Nanotube Problem
 |
Small-
angle neutron scattering pattern provides an inverted representation
of how carbon nanotubes flowing in a polymer melt sort themselves
by length. Longer nanotubes, which scatter neutrons at lower
angles, gather in purple regions, while medium-sized and
short nanotubes are indicated by red and yellow, respectively.
The dark blue circle in the center of the image is the beam
stop, which protects the sensitive detector from the transmitted
beam of unscattered neutrons.
Click
here for a high-resolution version of this image.
|
National
Institute of Standards and Technology (NIST) and university
researchers report a significant step toward sorting out the
nanotube “problem”—the challenge of overcoming
processing obstacles so that the remarkable properties of the
tiny cylindrical structures can be exploited in new polymer
composite materials of exceptional strength.
As described
in the July 15 issue of Physical Review Letters,* their
analysis reveals that, during mixing, carbon nanotubes suspended
in viscous fluids can be encouraged to sort themselves by length.
Achieving uniform sizes of nanotubes is one of several keys
to producing affordable, high-quality polymer nanocomposites.
The
team found that, under common processing conditions, shorter
carbon nanotubes will flow toward the walls of mixing equipment,
while the longer tubes tend
to congregate in the interior.
Better
understanding of factors that promote this self-sorting will
point the way to process adjustments
and devices that achieve desired arrangements
of
nanotubes during bulk manufacturing of polymer nanocomposites, says NIST’s
Erik Hobbie, leader of the collaboration, which included scientists from
the University of
Kentucky and Michigan Technical University.
Many times
stronger than steel and possessing superlative thermal, optical
and electronic properties, nanotubes have been called small-scale
wonders, measuring a few nanometers in diameter and ranging
greatly in length. Anticipated nanotube-based technologies range
from hydrogen storage to transistors to space elevators. Nearest
on the horizon are light-weight, high-strength carbon nanotube
polymer structural composites.
With lasers,
video microscopes and other optical monitoring equipment, the
team tracked how nanotubes—both the single-wall and multiwall
varieties—behave when suspended, at several different
concentrations, in a polymer melt. They analyzed suspensions
ranging in viscosity from syrup-like to watery under different
mixing conditions.
The results
did not suggest a “magic bullet” for getting nanotubes
to align uniformly in the same direction—also critical
to reliable processing of high-quality nanocomposites. But the
finding that, under “modest flow conditions,” carbon
nanotubes will sort by length could point the way to practical
methods for bulk separation of nanotubes according to size.
Further
information on nanotube-related research can be found at the
Polymers Division Web site at www.nist.gov/polymers.
*D. Fry,
B. Langhorst, H. Kim, E. Grulke, H. Wang, E.K. Hobbie. Anisotropy
of sheared carbon nanotube suspensions. Physical Review
Letters, 95, 038304 (July 15, 2005).
Bioagent
Detector Guide Aids First Responder Purchasing
Ever
since envelopes containing anthrax bacteria were mailed to
Congressional and media offices in 2001 causing several deaths,
many first responder departments have worked to improve their
ability to quickly detect toxic biological agents. To help
them make informed decisions about which biological agent
detection devices best meet their needs, the National Institute
of Standards and Technology (NIST) recently developed a two-volume
guide for the emergency response community. The guide, produced
for the Department of Homeland Security (DHS), does not make
recommendations. It provides the community with ways to compare
and contrast commercially available biological detection equipment.
Volume
1 of the Guide for the Selection of Biological Agent Detection
Equipment for Emergency First Responders presents an
historical overview of the use of biological agents starting
with the Assyrians who used ergot fungi to poison wells as
early as 600 B.C. It also describes various bacterial agents,
symptoms, effects and treatment as well as the challenges
of biological agent detection. The guide includes a market
survey of 143 biological agent detection products and commercially
available detectors known to the authors as of March 2005.
The guide also displays pictures of specific devices that
use the technology being discussed.
To help
first responders decide on appropriate equipment, the guide
cites 19 performance parameters or selection factors, including
sensitivity, specificity, start-up and response times, ease-of-use,
alarm capability, power requirements, skill level, cost, durability
and portability. An appendix lists questions that could assist
emergency first responders when selecting the biological agent
detection equipment. Volume II includes detailed detection
equipment data sheets.
DHS
intends to maintain and update the guide as new information
on biological
detection equipment becomes available. The Guide for
the Selection of Biological Agent Detection Equipment for
Emergency
First Responders is available at http://www.rkb.mipt.org.
After registration, type in "DHS AND guide" in the search
box. The link to the Bioagent Dectector Guide will be seen.
Media
Contact:
John
Blair, john.blair@nist.gov, (301) 975-4261
Compact
JILA System Stabilizes Laser Frequency
A compact,
inexpensive method for stabilizing lasers that uses a new
design to reduce sensitivity to vibration and gravity
100 times better than similar approaches has been demonstrated
by scientists at JILA in Boulder, Colo. JILA is a joint institute
of the National Institute of Standards and Technology (NIST)
and the University of Colorado at Boulder.
The method, described in the July 15 issue of Optics
Letters,*
stabilizes laser light to a single frequency, so that it can
be used as a reliable reference oscillator for technologies
such as optical clocks and light-based radar (lidar). The new
stabilizer design performs better than similar systems of comparable
size and is much smaller and less expensive than the best-performing
systems, according to physicist John Hall, a co-author of the
paper.
Laser systems
are highly sensitive to environmental disturbances, such as
electronic “noise” and vibration from soft drink
vending machines or other equipment with mechanical motors.
To stabilize operations in cases when high precision is needed,
lasers are often "locked" to a single wavelength/frequency
using an optical “cavity,” a small glass cylinder
with a mirror facing inward on each end. Laser light bounces
back and forth between the mirrors and, depending on the exact
distance between them, only one wavelength will "fit"
that distance best and be reinforced with each reflection. Information
from this stabilized laser light is then fed back to the laser
source to keep the laser locked on this one frequency. But the
cavity can vibrate, or expand in response to temperature changes,
causing corresponding slight frequency changes. Researchers
have tried various improvements such as using cavities made
of low-expansion glass.
In the
latest advance, the JILA team made the cavity shorter and positioned
it vertically instead of horizontally, with symmetrical mounting
supports so that gravity and vibration forces yield opposing
distortions in the two halves, and thus balance out to zero
net effect. The system was demonstrated with an infrared laser.
"We designed the cavity so it doesn't care if it's vibrating,"
says Hall, who helped develop a leading resonant cavity design
two decades ago. "We get good performance with a complete
reduction of complexity and cost."
The work
was supported by the Office of Naval Research, National Aeronautics
and Space Administration, National Science Foundation and NIST.
*M. Notcutt,
L.S. Ma, J. Ye, and J.L. Hall. 2005. Simple and compact 1-Hz
laser system via improved mounting configuration of a reference
cavity. Optics Letters. July 15.
Comments
Sought on Draft Federal IT Security Standard
To
help federal agencies improve their information technology
security and comply with the Federal Information Security
Management Act (FISMA) of 2002, the National Institute of
Standards and Technology (NIST) recently released for public
comment the draft of Federal Information Processing Standard
(FIPS) Publication 200, Minimum Security Requirements
for Federal Information and Information Systems.
FISMA requires all federal agencies to develop, document and
implement agency-wide information security programs and to
provide security for the information and information systems
that support the operations and assets of the agency. The act
called upon NIST to develop the standards and guidelines needed
for successful FISMA compliance.
The draft
FIPS Publication 200 is the third NIST publication of a three-part
series for this purpose. FIPS Publication 199, Standards
for Security Categorization of Federal Information and Information
Systems, issued in February 2004, requires agencies to
categorize their information and information systems as low
impact, moderate impact or high impact regarding confidentiality,
integrity and availability. NIST SP 800-53, Recommended
Security Controls for Federal Information Systems, issued
in February 2005, provides guidance on selecting the appropriate
controls for 17 key security focus areas.
FIPS Publication 200 provides: (1) a specification for minimum
security requirements for federal information and information
systems; (2) a standardized, risk-based approach (as described
in FIPS Publication 199) for selecting security controls in
a cost-effective manner; and (3) links to NIST Special Publication
800-53.
NIST invites public comments on the draft standard until 5
p.m. Eastern Daylight Time on Sept. 13, 2005. The document
may be downloaded at http://csrc.nist.gov/publications/drafts.html.
Media
Contact:
Michael
E. Newman, michael.newman@nist.gov,
(301) 975-3025
Quick
Links
Measurement
Challenges In Detecting Cancer Biomarkers
In
cancer research, biomarkers are molecules that indicate
the presence of cancer in the body. Most are based
on abnormal changes or mutations in genes, RNA, proteins
and metabolites. Since the molecular changes that
occur during tumor development can take place over
a number of years, biomarkers potentially can be used
to detect cancers early, determine prognosis and monitor
disease progression and therapeutic response. Candidate
biomarkers, however, frequently are found only in
relatively low concentrations amid a sea of other
biomolecules, so both biomarker research and possible
diagnostic tests depend critically on the ability
to make highly sensitive and accurate biochemical
measurements.
A
special August workshop at the National Institute
of Standards and Technology (NIST) will examine the
measurement challenges posed by two important biomarker
classes, measurement of DNA methylation and serum
proteomics. The addition of methyl groups (a molecule
with one carbon and three hydrogen atoms) at certain
key sites on DNA is known to alter the expression
of genes, and might serve as an indicator of when
cancer-related genes are “turned on or off.”
Serum proteomics involves reliably detecting trace
levels of proteins associated with cancer cells. Both
approaches have been hampered by the lack of reproducibility
and consistency in measurements.
The
workshop on Standards, Methods, Assays, Reagents and
Technologies (SMART) for Early Cancer Detection and
Diagnosis, jointly sponsored by NIST and the Early
Detection Research Network (EDRN) of the National
Cancer Institute will compare the performance characteristics
of different analytical platforms for DNA methylation
and serum proteomics, assess the needs for standard
methods, assays and reagents for cancer biomarker
development and validation, and make recommendations
for the development of Standard Reference Materials
and standard operating procedures. The SMART workshop
will be held at the NIST site in Gaithersburg, Md.,
from Aug. 18-19, 2005. Details are available at www.nist.gov/public_affairs/confpage/050818.htm. Reporters planning to attend should
contact Michael Baum, michael.baum@nist.gov, (301)
975-2763.
Draft
Guidelines Released for IT Security Controls
To
help federal agencies comply with the Federal Information
Security Management Act (FISMA) of 2002, the National
Institute of Standards and Technology (NIST) issued
Special Publication 800-53, Recommended Security
Controls for Federal Information Systems, in
February 2005. NIST SP 800-53 provides guidance on
selecting security controls for information systems
in key areas such as risk assessment, contingency
planning, and identification and authentication. A
companion document, NIST SP 800-53A, Guide for
Assessing the Security Controls in Federal Information
Systems, has been drafted to help agencies take
the next step: assessing the effectiveness of security
controls once they are in place. NIST invites public
comments on this draft guideline until 5 p.m. Eastern
Daylight Time on Aug. 31, 2005. NIST SP 800-53A, and
instructions on how to submit comments on it, may
be found at http://csrc.nist.gov/publications/drafts.html.
NIST’s
Manufacturing Lab Prints 2005 Program Guide
With
a value-added contribution of $1.4 trillion, U.S.
manufacturing directly accounts for approximately
13 percent of the U.S. gross domestic product. The
National Institute of Standards and Technology's (NIST)
Manufacturing Engineering Laboratory (MEL) has just
released its annual 2005 guide to programs serving
that critical national sector. The publication summarizes
MEL work in dimensional metrology, homeland and industrial
control security, intelligent control of mobility
systems, manufacturing interoperability, manufacturing
metrology and standards for health care enterprise,
mechanical metrology, nanotechnology and smart machining
systems. Each program notes the resources, objectives,
customer needs addressed, accomplishments, current
year plans, lifetime objectives and related measurement
and standards work. Special MEL activities also are
reviewed, including the laboratory's role in the international
Intelligent Manufacturing Systems (IMS) program, Systems
Integration for Manufacturing Applications (SIMA)
and the National Science and Technology Council Interagency
Working Group on Manufacturing Research and Development.
MEL: The Programs of the Manufacturing Engineering
Laboratory 2005 (NISTIR 7218) is available at
www.mel.nist.gov/proj/pdf/bb05web.pdf (.pdf;
download Acrobat Reader).
For a paper copy, contact Lisa Fronczek at lfronczek@nist.gov.
Usability
Standard Achieves International Status
Software
that is poorly designed, inappropriate for specific
tasks or just difficult to use can be frustrating,
unproductive and costly for both businesses and individuals.
To help remedy the problem, computer scientists at
the National Institute of Standards and Technology
(NIST) have been working for several years with private
industry, including The Boeing Co., Oracle Corp.,
and Microsoft Corp. to develop a standard way to test
and evaluate software usability. The resulting effort,
the Common Industry Format (CIF) for Usability Test
Reports, recently was approved as a worldwide standard
by the Software and Systems Engineering Committee
of the International Organization for Standardization.
For more information on CIF, see www.nist.gov/iusr.
|
