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Nano-antennas Improve Infrared Sensing

Nano-antennas Improve Infrared Sensing | Spheres | Scoop.it

A team of University of Pennsylvania engineers has used a pattern of nanoantennas to develop a new way of turning infrared light into mechanical action, opening the door to more sensitive infrared cameras and more compact chemical-analysis techniques.

 

The research was conducted by assistant professor Ertugrul Cubukcu and postdoctoral researcher Fei Yi, along with graduate students Hai Zhu and Jason C. Reed, all of the Department of Material Scienceand Engineering in Penn’s School of Engineering and Applied Science.  

 

Detecting light in the mid-infrared range is important for applications like night-vision cameras, but it can also be used to do spectroscopy, a technique that involves scattering light over a substance to infer its chemical composition. Existing infrared detectors use cryogenically cooled semiconductors, or thermal detectors known as microbolometers, in which changes in electrical resistance can be correlated to temperatures. These techniques have their own advantages, but both need expensive, bulky equipment to be sensitive enough for spectroscopy applications.

 

“We set out to make an optomechanical thermal infrared detector,” Cubukcu said. “Rather than changes in resistance, our detector works by connecting mechanical motion to changes in temperature.”

 

The advantage to this approach is that it could reduce the footprint of an infrared sensing device to something that would fit on a disposable silicon chip. The researchers fabricated such a device in their study.

 

At the core of the device is a nanoscale structure — about a tenth of a millimeter wide and five times as long — made of a layer of gold bonded to a layer of silicon nitride. The researchers chose these materials because of their different thermal expansion coefficients, a parameter that determines how much a material will expand when heated. Because metals will naturally convert some energy from infrared light into heat, researchers can connect the amount the material expands to the amount of infrared light hitting it.    

 

“A single layer would expand laterally, but our two layers are constrained because they’re attached to one another,” Cubukcu said. “The only way they can expand is in the third dimension. In this case, that means bending toward the gold side, since gold has the higher thermal expansion coefficient and will expand more.”

 

To measure this movement, the researchers used a fiber interferometer. A fiber optic cable pointed upward at this system bounces light off the underside of the silicon nitride layer, enabling the researchers to determine how far the structure has bent upwards. 

 

“We can tell how far the bottom layer has moved based on this reflected light,” Cubukcu said. “We can even see displacements that are thousands of times smaller than a hydrogen atom.”


Via Dr. Stefan Gruenwald
Tom Leckrone's insight:

Excerpt: “A single layer would expand laterally, but our two layers are constrained because they’re attached to one another,” Cubukcu said. “The only way they can expand is in the third dimension. In this case, that means bending toward the gold side, since gold has the higher thermal expansion coefficient and will expand more.”

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'Tree of life' constructed for all living bird species

'Tree of life' constructed for all living bird species | Spheres | Scoop.it

Scientists have mapped the evolutionary relationships among all 9,993 of the world's known living bird species. The study is an ambitious project that uses DNA-sequence data to create a phylogenetic tree — a branching map of evolutionary relationships among species — that also links global bird speciation rates across space and time.

 

“This is the first dated tree of life for a class of species this size to be put on a global map,” says study co-author Walter Jetz, an evolutionary biologist at Yale University in New Haven, Connecticut.

 

But the endeavour is also controversial, owing to the large number of species for which no sequence data are available. “This is a conceptually brilliant attempt to link space with time while crafting a complete phylogeny,” says Trevor Price, an evolutionary biologist at the University of Chicago in Illinois. “But there are almost certainly introduced artefacts by lacking one-third of the sequences used to create it.”

 

Jetz and his colleagues built on an extensive phylogenomic study, published in 2008, to divide bird species into 158 clades, well-established groups believed to have evolved from a common ancestor2. Using ten fossils, the researchers dated and anchored that backbone, and placed all the living species on the tree, starting with the roughly 6,600 for which genetic information was available. For the remaining 3,330 species for which no genetic data were available, the researchers used specific constraints — such as membership in the same genus — to identify where species would most likely be placed in the tree. They then created thousands of possible tree configurations and modeled estimates of speciation and extinction rates for each one to account for the uncertainty. The researchers found that although rapid radiations have occurred throughout time and space, the rate of speciation has sharply increased over the past 40 million years.

 

Some scientists question the finding. “For a tree this size, any small systematic biases in assumptions, integrated over 10,000 species, may result in the detection of trends that simply didn’t exist,” says Mark Pagel, an evolutionary biologist at the University of Reading, UK. But when the researchers repeated the analysis using only species for which genetic data exists, they saw roughly the same pattern.


Via Dr. Stefan Gruenwald
Tom Leckrone's insight:

Brilliant and bold approach to unify understanding of bird evolution using computer modeling, which essentially extrapolated known genetic info over the one third of total species for which we have no genetic data. 

There will clearly be individual relations suggested by this beautiful "tree" that are not borne out by future study. But the very effort of laying out a unified view will aid further investigation. 

**Note the usefulness of the circular lay-out in conveying diverse relationships over time.

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Middle Earth: Why We Need to Turn Our Map on Its Side

Middle Earth: Why We Need to Turn Our Map on Its Side | Spheres | Scoop.it
Though he never actually crossed it, the Greek mathematician Pythagoras is sometimes credited with having first conceived of the Equator, calculating its location on the Earth’s sphere more than four centuries before the birth of Christ.

Via Tony Hall, Seth Dixon
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Seth Dixon's curator insight, May 24, 2013 7:48 AM

This is an interesting article on some Earth-Sun relationships that challenges the dominant north-centered normative view of how to think about our planet.  My favorite tidbit of information: "The velocity of the Earth’s rotation varies depending on where you stand: 1,000 mph at the Equator versus almost zero at the poles. That means that the fastest sunrises and sunsets on the planet occur on the Equator, and centrifugal and inertial forces are also much greater there. "

Mike Busarello's Digital Storybooks's comment, May 24, 2013 11:09 AM
Great article to include in our summer assignment packet!
Steven Flis's curator insight, December 17, 2013 3:42 PM

Definitly changed my way of thinking. also this brings up the many flaws with pre geospatial desinged maps. cartographers could push their own agenda to make their country or area look more promient than it actually is. also another prime example of something that has been taken as fact for many years (nobody questions a world map) and turns out to have some flaws

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Tailoring optical processors: Arranging nanoparticles in geometric patterns allows for control of light with light

Tailoring optical processors: Arranging nanoparticles in geometric patterns allows for control of light with light | Spheres | Scoop.it
Rice University scientists have unveiled a robust new method for arranging metal nanoparticles in geometric patterns that can act as optical processors that transform incoming light signals into output of a different color.

 

Rice's team used the method to create an optical device in which incoming light could be directly controlled with light via a process known as "four-wave mixing." Four-wave mixing has been widely studied, but Rice's disc-patterning method is the first that can produce materials that are tailored to perform four-wave mixing with a wide range of colored inputs and outputs.

 

"Versatility is one of the advantages of this process," said study co-author Naomi Halas, director of LANP and Rice's Stanley C. Moore Professor in Electrical and Computer Engineering and a professor of biomedical engineering, chemistry, physics and astronomy. "It allows us to mix colors in a very general way. That means not only can we send in beams of two different colors and get out a third color, but we can fine-tune the arrangements to create devices that are tailored to accept or produce a broad spectrum of colors."

 

The information processing that takes place inside today's computers, smartphones and tablets is electronic. Each of the billions of transistors in a computer chip uses electrical inputs to act upon and modify the electrical signals passing through it. Processing information with light instead of electricity could allow for computers that are both faster and more energy-efficient, but building an optical computer is complicated by the quantum rules that light obeys.


Via Dr. Stefan Gruenwald
Tom Leckrone's insight:

Brilliant! Non-linear = omnidirectional! I see enticing applications for process analysis, signal mixing and patten optimization within networks/communities! 

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Tom Leckrone's comment, May 26, 2013 9:37 AM
Brilliant (truly)! We are moving ever closer to Indra's Net.
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The Digital Reorganization Chart

The Digital Reorganization Chart | Spheres | Scoop.it
The Digital Reorganization Chart is the first of three reports on the reorganization of government using network principles
Tom Leckrone's insight:
Nice breakdown of creating a REorganization Chart. Excerpt: "To start the process of smart reorganization, first the enterprise needs an accurate picture of itself. Ask anyone in an organization for its org chart and typically you’re handed a piece of paper—or sent to a website—with a box-and-wire diagram showing a few dozen positions. Whether the organization in question has fifty employees or 50,000, the charts generally look the same—and the request for one rarely, if ever, produces an accurate map of the whole thing.What this means is that the vast majority of people in control are running organizations whose true size, shape, and structure they never really see."

Let Sempre Phi guide your leaders in shaping an organizational model that truly portrays all of its facets. As the model comes to life, your communities will gain increasingly powerful ways to engage with the organization as a holistic, dynamic enterprise.

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