Current
Smoke Alarms Pass Life-Saving Tests
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Fire test in progress at the NIST Large
Fire Facility.
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Today’s
home smoke alarms—both ionization and photoelectric types—consistently
provide enough time for people to escape most fires. Immediate
response to an alarm, however, is critical, since the tests
affirmed previous findings that individuals caught in a flaming
fire (as opposed to a smoldering fire) have only an average
of three minutes to escape untenable or unsurvivable conditions.
Those are the key conclusions of a two-year National Institute
of Standards and Technology (NIST) study, the first comprehensive
look at smoke alarms since NIST tests 25 years ago.
“The
three-minute escape window for flaming fires differs from the
17 minutes NIST recorded in its seminal smoke alarm tests in
the 1970s,” said Richard Bukowski, the NIST researcher
who conducted both studies. “It confirms what fire scientists
have recognized for some time: fires today seem to burn faster
and kill quicker because the contents of modern homes (such
as furnishings) can burn faster and more intensely. Our new
research, however, proves that even with a three-minute warning,
smoke alarms still offer enough time to save your life,”
Bukowski stressed. “When the alarm sounds, it is important
that everyone just get out of the house.”
NIST found
that ionization smoke detectors activate quicker for flaming
fires than photoelectric alarms. Photoelectric alarms, on the
other hand, often provide faster response time to smoldering
fires. Placement of either type on every level of the house
would save lives. The tests also showed how closed bedroom doors
and proper placement of smoke alarms improved prospects for
survival. In both cases, time to escape untenable conditions
increased, providing the individual was not in the room where
the fire originated.
The study
was sponsored and supported with in-kind contributions by eight
federal and non-profit
agencies.
To download
the full report,* visit http://smokealarm.nist.gov.
*Bukowski,
Richard, et al., Performance of Home Smoke Alarms, Analysis
of the Response of Several Available Technologies in Residential
Fire Settings
Media
Contact:
John
Blair, (301) 975-4261
Tagging
Faulty Genes With Fluorescent Nanodots
A
nanoscale imaging technique that could improve the reliability
of an important diagnostic test for breast cancer, and other biomedical
tests, is described by National Institute of Standards and Technology
(NIST) researchers in the Feb. 11 online issue of Nucleic
Acids Research.
The
method involves attaching fluorescent particles just 15 nanometers
(billionths of a meter) in diameter to particular sections of
DNA, followed by analysis of the intensity
of the fluorescence signal and other properties. These particles,
called quantum dots, have unique electronic and optical properties
that make them easier to detect than conventional fluorescent
tags used in biomedical research. The NIST team demonstrated that
quantum dots give off signals that are 200 to 1,100 percent more
intense than those from two types of conventional tags, and also
are more stable when exposed to light.
The
new technique is a spin-off of an ongoing NIST effort to develop
standards for a test that identifies breast cancer patients who
would benefit from a particular drug therapy. The standards are
expected to help reduce uncertainty in the so-called FISH (fluorescence
in situ hybridization) test that detects a particular gene. Excess
copies of this gene result in over-production of a protein and
cause tumor cells to grow rapidly. Potentially, quantum dots could
be used to tag these genes.
The
quantum dots used in the study are commercially available aggregates
of semiconductor materials, which, even though they contain hundreds
to thousands of atoms, behave like single atoms electronically.
Quantum dots absorb light efficiently over a wide frequency range
and re-emit it at a single wavelength (or color) that depends
on particle size.
The
NIST research is supported in part by the National Institutes
of Health.
Media
Contact:
Laura Ost, (301) 975-4034
Quantum
Dots Deliver Photons One at a Time
 |
| Electrical
engineer Richard Mirin aligns a laser used in an apparatus
for producing a stream of single photons.
© Geoffrey Wheeler
|
A
National Institute of Standards
and Technology (NIST) scientist has demonstrated efficient production
of single photons—the smallest pulses of light—at
the highest temperatures reported for the photon source used.
The advance is a step toward practical, ultrasecure quantum
communications, as well as useful for certain types of metrology.
The results are reported in the Feb. 23 issue of Applied
Physics Letters.
“Single
photon turnstiles” are being hotly pursued for quantum
communications and cryptography, which involve using streams
of individual photons in different quantum states to transmit
encoded information. Due to the peculiarities of quantum mechanics,
such transmissions could not be intercepted without being altered,
thus ensuring that eavesdropping would be detected.
The photon
source used in the NIST study was a “quantum dot,”
10 to 20 nanometers wide, made of semiconductor materials. Quantum
dots have special electronic properties that, when excited,
cause the emission of light at a single wavelength that depends
on dot size. An infrared laser tuned to a particular wavelength
and intensity was used to excite the quantum dot, which produced
photons one by one more than 91 percent of the time at temperatures
close to absolute zero (5 K or about minus 459 degrees F) and
continued to work at 53 percent efficiency at 120 K (minus 243
degrees F). Higher operating temperatures are preferable from
a cost standpoint, because the need for cooling is reduced.
The NIST
quantum dots are made of indium gallium arsenide, can be fabricated
easily, and can be integrated with microcavities, which increase
photon capture efficiency. According to NIST electrical engineer
Richard Mirin, this design offers advantages over other single
photon sources, many of which exhibit blinking, stop working
under prolonged exposure to light or are difficult to fabricate.
Media
Contact:
Laura Ost, (301) 975-4034
Using
Water as a Lens To Shrink Chip Dimensions
Thanks
in part to highly accurate measurements made by National Institute
of Standards and Technology (NIST) researchers, semiconductor
manufacturers will be able to pursue a new production method
that will enable them to produce new generations of computer
chips using existing equipment—saving the industry hundreds
of millions of dollars.
Creating
ever more powerful computer chips relies on being able to increasingly
miniaturize the features on
those chips. Industry had thought it might be nearing the end
of the useful life of equipment that creates features using
193 nanometer (nm) wavelength light.
However,
a new method called immersion lithography uses a thin layer
of water like a lens to shorten the effective wavelengths of
ultraviolet light used in patterning semiconductor chips. The
method relies on the fact that light travels slower through
water than air. The frequency of the light remains the same,
so the distance between peaks (the wavelength) must shorten
to compensate.
The method
should enable manufacturers to use 193 nm equipment to create
circuit lines and other features at least as small as 45 nm.
Such a breakthrough allows manufacturers to create much more
powerful chips while getting more life out of their current
fabrication equipment, which can cost around $20 million per
tool.
The industry
began to take immersion lithography seriously about a year ago.
With the support of International SEMATECH, the semiconductor
industry’s R&D consortium, NIST scientists made highly
accurate measurements of a property called refractive index,
a measure of how much ultraviolet light at a wavelength of 193
nm bends when it moves from air to water. This new data helped
enable the semiconductor industry to design immersion lithography
systems.
NIST researchers
described key results of their work at the International Society
for Optical Engineering’s Microlithography 2004 conference
held Feb. 23-28 in Santa Clara, Calif.
The researchers
also are working with industry on new immersion fluids for 157
nm wavelength chipmaking tools, so that this equipment can produce
features of 32 nm or below.
Media Contact:
Scott Nance, (301) 975-5226
Standardizing
Disaster Models To Help First Responders
Computer
modeling and simulation programs that depict predisaster site
conditions, changes due to sudden life-threatening events
and consequences of emergency responses can be powerful tools
for preparing for and coping with everything from terrorist
attacks to hurricanes. Yet the multitude of programs, incompatibility
of systems as well as technical jargon in the programs themselves
hinder widespread acceptance of the potentially life-saving
technology. The National Institute of Standards and Technology
(NIST) is working to make such modeling and simulation programs
readily accessible to emergency response decision-makers.
NIST
is identifying the needs of emergency personnel and surveying
the available modeling and simulation tools. It also proposes
simplifying language in emergency response software to enable
emergency personnel, at every level, to use the tools. In
addition, NIST advocates industry-government efforts to develop
interoperability standards for all modeling, simulation and
visualization tools. Finally, NIST supports creation of an
electronic “Emergency Response Framework” for
such standardized programs. The framework would present state,
local and national level decision-makers with a comprehensive
menu of easily accessible modeling and simulation programs
for understanding the extent of various threats, for training
on mitigating damage to life and property and for coordinating
emergency responses to actual events. NIST is currently working
with other government researchers, industry software experts
and emergency response leaders on a roadmap and development
plan for the framework.
For
background information, see Modeling and Simulation for
Emergency Response: Workshop Report, Standards and Tools,
a NIST report, published this month, of a 2003 workshop at
NIST. The report is available at www.nist.gov/simresponse.
Media
Contact:
John
Blair, (301) 975-5661
