(Press-News.org) Contact information: Angela Stark
astark@osa.org
202-416-1443
The Optical Society
Fur and feathers keep animals warm by scattering light
New work suggests that fur coats and down feathers might derive much of their impressive insulating power from an unexpected optical mechanism
WASHINGTON, Jan. 23—In work that has major implications for improving the performance of building insulation, scientists at the University of Namur in Belgium and the University of Hassan I in Morocco have calculated that hairs that reflect infrared light may contribute significant insulating power to the exceptionally warm winter coats of polar bears and other animals. The research was published today in The Optical Society's (OSA) open-access journal, Optics Express.
Biophotonics expert Priscilla Simonis, a researcher at the University of Namur and lead author of the Optics Express paper, was intrigued by the ability of polar bears to insulate their bodies to temperatures of 37 degrees Celsius (98.6 F) even during long, cold winters when outside temperatures are a frigid -40 C (-40 F). The feat was especially impressive given that the bears have a layer of fur that is only 5 centimeters thick.
The insulating power of the animals' coats made Simonis wonder why thermal insulation in buildings doesn't work as well. "Why do we need at least 60 cm of rockwool or glasswool" – common types of building insulation made from minerals or glass fibers – "to get a temperature of 20 degrees Celsius inside from about -5 degrees Celsius outside?" she asked. "Why is the polar bear fur much more efficient than what we can develop for our housing?"
Simonis and her team tackled the question by re-examining two of the different ways heat can travel: radiation, which transfers thermal energy through electromagnetic waves, and conduction, which transfers thermal energy through the vibrations of neighboring atoms and molecules. Most people assume that fur and feathers keep animals warm primarily by trapping a layer of air that slows thermal conduction, says Simonis. But she and her colleagues suspected that radiation might play a bigger role.
The scientists performed some initial calculations that showed heat loss between two bodies separated by air would be dominated by radiation, not conduction. To further explore the radiative heat loss the team created a simple computer model consisting of a hot and a cold thermostat that roughly simulated an animal's warm body and the outside, colder environment. The two thermostats were separated by an empty space into which were added "radiative shields" that could mimic individual hairs in a fur coat.
In one version of the model, the researchers incorporated so-called black-body shields, which absorb all of the radiation that strikes them. In a second version, opaque grey-body shields were used. "A grey body has some transmission and reflection as well," Simonis explains.
Simonis and her colleagues found that as the reflectivity of the radiative shields increased, the rate of heat transfer between the hot and cold thermostat was dramatically reduced. Adding more shields also dramatically reduced the energy loss. All together, the model suggests that the repeated backscattering of infrared light between radiative shields, like individual hairs and barbed feathers, could be the primary mechanism for the thermal insulation properties of fur and feathers.
The light scattering properties of animals' coats can also have dual purposes, Simonis notes. With the right structure, fur and feathers can generate efficient thermal insulation in the far infrared range while also scattering visible light to produce a white appearance in the visible wavelength range. "This is particularly useful to animals, such as mammals and birds, that live in snowy areas," Simonis says, as it provides them with both warmth and camouflage against the white snow.
For humans, focusing on ways to minimize radiative heat loss could lead to the development of new types of ultrathin insulation. "The idea is to multiply the interaction of electromagnetic waves with grey bodies – reflecting bodies, like metals, with very low emissivity and no transparency – in a very thin material," Simonis says. "It can be done by either a multilayer or a kind of 'fur' optimized for that purpose."
INFORMATION:
Paper: "Radiative contribution to the thermal conductance in animal furs and other wooly insulators," Simonis, P. et al., Optics Express, Vol. 22, Issue 2, pp. 1940-1951 (2014)
EDITOR'S NOTE: High-resolution images are available to members of the media upon request. Contact Angela Stark, astark@osa.org.
About Optics Express
Optics Express reports on new developments in all fields of optical science and technology every two weeks. The journal provides rapid publication of original, peer-reviewed papers. It is published by the Optical Society and edited by Andrew M. Weiner of Purdue University. Optics Express is an open-access journal and is available at no cost to readers online at http://www.OpticsInfoBase.org/OE.
About OSA
Founded in 1916, The Optical Society (OSA) is the leading professional society for scientists, engineers, students and business leaders who fuel discoveries, shape real-world applications and accelerate achievements in the science of light. Through world-renowned publications, meetings and membership programs, OSA provides quality research, inspired interactions and dedicated resources for its extensive global network of professionals in optics and photonics. For more information, visit http://www.osa.org.
Fur and feathers keep animals warm by scattering light
New work suggests that fur coats and down feathers might derive much of their impressive insulating power from an unexpected optical mechanism
2014-01-23
ELSE PRESS RELEASES FROM THIS DATE:
Are enough women included in medical device studies, as required by the FDA?
2014-01-23
New Rochelle, NY, January 23, 2013-The U.S. Food and Drug Administration (FDA) mandates adequate enrollment of women in post-approval studies (PAS) of medical ...
Practice makes perfect if you have a partner's touch, according to new study
2014-01-23
People improve their performance more when they practise with a partner rather than on their own, according to a new study.
The research could ultimately help people rehabilitating ...
Natural History Museum, London, yields remarkable new beetle specimens from Brazil
2014-01-23
A visit to the Natural History Museum, London, yielded an unexpected surprise for Dr. Joseph Parker, a UK biologist based in New York at Columbia University and the American Museum of Natural History.
Among ...
Death row confessions and the last meal test of innocence
2014-01-23
Can last meals reveal more about individuals on death row than their taste preference? Some have argued there is significance embedded in death row last meal decisions. Famously, Ricky Ray Rector asked to save his untouched ...
2 proteins compete for 1 port on a growth factor; 1 promotes metastasis, the other blocks it
2014-01-23
HOUSTON – Consider two drivers, each with ...
The $125 billion question: How will the ACA affect cancer survivors?
2014-01-23
In 2010, the total cost of cancer care in the United States reached $125 billion. Globally, the economic toll from cancer is nearly 20 percent higher than the leading cause of death, ...
Looking for a 'superhabitable' world? Try Alpha Centauri B, says Astrobiology Journal
2014-01-23
New Rochelle, January 23, 2014—The search for extraterrestrial life extends far beyond Earth's solar system, looking for planets or moons outside the ...
Better eating habits, not bad economy, stabilized obesity rates
2014-01-23
All those people who've been telling us for years that we should eat more healthy foods and cut our calories – stop, take a moment, and celebrate.
It appears that we actually ...
Scripps Florida scientists find regulator of amyloid plaque buildup in Alzheimer's disease
2014-01-23
JUPITER, FL – January 23, 2014 – Scientists from the Florida campus of The Scripps Research Institute have identified a critical regulator of a molecule deeply involved ...
Physical activity significantly extends lives of cancer survivors
2014-01-23
MAYWOOD, Il. – Physical activity significantly extends the lives of male cancer survivors, a new study of 1,021 men has found.
During the period while the ...
LAST 30 PRESS RELEASES:
New study finds that, after a heart attack, women have worse prognosis when treated with beta-blockers
CNIC-led REBOOT clinical trial challenges 40-year-old standard of care for heart attack patients
Systolic blood pressure and microaxial flow pump–associated survival in infarct-related cardiogenic shock
Beta blockers, the standard treatment after a heart attack, may offer no benefit for heart attack patients and women can have worse outcomes
High Mountain Asia’s shrinking glaciers linked to monsoon changes
All DRII-ed up: How do plants recover after drought?
Research on stigma says to just ‘shake it off’
Scientists track lightning “pollution” in real time using NASA satellite
Millions of women rely on contraceptives, but new Rice study shows they may do more than just prevent pregnancy
Hot days make for icy weather, Philippine study finds
Roxana Mehran, MD, receives the most prestigious award given by the European Society of Cardiology
World's first clinical trial showing lubiprostone aids kidney function
Capturing language change through the genes
Public trust in elections increases with clear facts
Thawing permafrost raised carbon dioxide levels after the last ice age
New DNA test reveals plants’ hidden climate role
Retinitis pigmentosa mouse models reflect pathobiology of human RP59
Cell’s ‘antenna’ could be key to curing diseases
Tiny ocean partnership between algae and bacteria reveals secrets of evolution
Scientists uncover cellular “toolkit” to reprogram immune cells for cancer therapy
Blocking protein control pathway slows rhabdomyosarcoma growth in mice
2026 Hertz Fellowship Application Now Open
The gut immune system is altered in mouse model of Alzheimer’s, providing a new target for therapeutics
ADHD drugs are being prescribed too quickly to preschoolers
UCLA scientists develop off-the-shelf immunotherapy for metastatic kidney cancer
Extreme heat linked to spike in domestic violence calls in New Orleans, study finds
Mount Sinai-Duke University study identifies DNA variants that increase testosterone production in PCOS patients
Physiology-guided complete revascularization in older patients with myocardial infarction
Metals and sulfate in air pollution mixture may contribute most to asthma hospitalizations
Understanding the profound yet hidden effects of neglect on white matter structures
[Press-News.org] Fur and feathers keep animals warm by scattering lightNew work suggests that fur coats and down feathers might derive much of their impressive insulating power from an unexpected optical mechanism