How bats avoid collisions

March 30, 2010 By Leave a Comment

Washington, March 30 (ANI): A study led by Brown University researchers has discovered how bats avoid collisions.

For the study, James Simmons, a professor of neuroscience at Brown University, and his colleagues at Brown and in Japan, conducted a series of innovative experiments designed to mimic a thick forest.

Their research has appeared in the Proceedings of the National Academy of Sciences early edition.

According to the researchers, echolocating bats minimize sound wave interference by tweaking the frequencies of the sounds they emit – their broadcasts – to detect and maneuver around obstacles.

They also found that bats make mental templates of each broadcast and the echo it creates, to differentiate one broadcast/echo set from another.

The research may lead to the design of better sonar and radar systems by capitalizing on the bats” natural ability to ferret out duplicative echoes in environments that otherwise could produce “phantom” objects.

The scientists created a 13-row long by 11-row wide U-shaped grid of ceiling-to-floor chain links to test big brown bats” ability to locate obstacles at various distances in their flight path and to make nearly instantaneous adjustments.

They used a miniature radio microphone created by their Japanese colleagues and attached it to the bats” heads to record their sounds (which are made in pairs).

Other microphones placed in the room recorded the echoes produced from the bats” broadcasts, giving the researchers a comprehensive, accurate recording of the bats” echo-processing methods.

The scientists also filmed the bats with high-resolution video cameras.

The team noticed almost immediately that the bats were confronted with overlapping echoes to their rapid firing of broadcasts. That could create confusion where obstacles were located and even produce objects that weren”t really there.

Mary Bates, a fourth-year graduate student at Brown and a contributing author on the paper, said: “When there are a lot of obstacles in the environment, a bat needs to emit sounds quickly.

“It can”t wait for another sound to return before updating its image” (of the scene in which it”s flying).

An echo from the bat”s first broadcast could masquerade as the echo from a subsequent broadcast.

The bat overcomes this potentially confusing cascade of signals by making a template, or mental fingerprint, of each broadcast and corresponding echo, the team learned. That way, the bat needs only to slightly alter the frequency of its broadcast to create a broadcast/echo template that doesn”t match the original.

The team found that bats change the frequency of their broadcasts by no more than 6 kilohertz. That”s a good thing, as bats” frequency range covers only roughly 20 to 100 kilohertz.

Simmons said: “They”ve evolved this, so they can fly in clutter.

“Otherwise, they”d bump into trees and branches.” (ANI)

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Quake experts develop new system to monitor underground movements

September 1, 2009 By Leave a Comment

London, Aug 31 (ANI): A five-strong group of scientists have developed a new technique that can monitor movements beneath the earth’s surface to help understand how earthquakes behave.

The scientists, led by Andrew Curtis, Professor of Mathematical Geoscience at Edinburgh University, used computers to simulate the motion of one earthquake at the location of another to discover more in-depth information about underground movements.

They used information from seismometers – which collect data on earthquakes – to develop the technique.

The method also increases the number of locations that could be used to detect seismic activity.

“This turns the way we listen to seismic movements on its head. By using earthquakes themselves as virtual microphones that record the sound of the earth’s internal movements, we can listen to the earth’s stretching and cracking from directly within its most interesting dynamic places,” the Scotsman quoted Curtis as saying.

“The key to the new method is understanding the theory of sound waves. It’s more about back-projection – which is when we use a computer to send the sound wave of an earthquake down to the epicentre of another earthquake in order to measure the movements more precisely,” he added. (ANI)

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Now, acoustic tweezers to position tiny objects

August 29, 2009 By Leave a Comment

Washington, Aug 29 (ANI): While it gets quite difficult to manipulate tiny objects like single cells or nanosized beads via relatively large, unwieldy equipment, Penn State engineers have now designed a new system that uses sound as a pair of tiny tweezers that are small enough to place infinitesimal objects on a chip.

While optical tweezers are large and expensive, acoustic tweezers are smaller than a dime, small enough to fabricate on a chip using standard chip manufacturing techniques.

They can also manipulate live cells without damaging or killing them.

“Current methods for moving individual cells or tiny beads include such devices as optical tweezers, which require a lot of energy and could damage or even kill live cells. Acoustic tweezers are much smaller than optical tweezers and use 500,000 times less energy,” said Tony Jun Huang, assistant professor of engineering science and mechanics.

Acoustic tweezers differ from eyebrow tweezers in that they position many tiny objects simultaneously, and place them equidistant from each other in either parallel lines or on a grid.

And the grid configuration of acoustic tweezers is probably the most useful for biological applications where researchers can place stem cells on a grid for testing or skin cells on a grid to grow new skin, which allows them to see how any type of cell grows.

“Acoustic tweezers are not just useful in biology. They can be used in physics, chemistry and materials science to create patterns of nanoparticles for coatings or to etch surfaces,” said Huang.

Acoustic tweezers work by setting up a standing surface acoustic wave.

If two sound sources are placed opposite each other, and each emits the same wavelength of sound, there will be a location where the opposing sounds cancel each other and it can be considered a trough.

As sound waves have pressure, they can push very small objects, so a cell or nanoparticle will move with the sound wave until it reaches the trough where there is no longer movement and thus the particle or cell will stop and “fall” into the trough.

If the sound comes from two parallel sound sources facing each other, the troughs form a line or series of lines.

If the sound sources are at right angles to each other, the troughs form an evenly spaced set of rows and columns like a checkerboard. Here too, the particles are pushed until they reach the location where the sound is no longer moving.

The acoustic tweezers are manufactured by fabricating an interdigital transducer onto a piezoelectric chip surface. The transducers are the source of the sound.

Using standard photolithography, microchannels are fabricated in which a small amount of liquid with the cells or particles can move around freely.

These microchannels were bonded to the chip to create the area for particle movement.

For testing the device, the researchers, used Dragon Green fluorescent polystyrene beads about 1.9 micrometers in diameter before using cows red blood cells and the single cell bacteria E. coli.

“The results verify the versatility of our technique as the two groups of cells differ significantly in both shape (spherical beads vs. rod-shaped E. coli) and size,” said the researchers

Acoustic tweezers technology has significant advantages over existing technologies because of its versatility, miniaturization, power consumption, and technical simplicity.

According to Huang, it could become a powerful tool for applications like tissue engineering, cell studies, and drug screening and discovery.

The study has been published in a recent issue of Lab on a Chip. (ANI)

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Scientists solve age-old mystery of horseshoe bat’s elongated nose

July 8, 2009 By Leave a Comment

Washington, July 8 (ANI): Scientists have solved the mystery of a bat with an extraordinarily long nose, by determining that the creature uses its elongated nose to create a highly focused sonar beam, which helps in the detection of its environment.

The bat, called the Bourret’s horseshoe bat (known scientifically as the “Rhinolophus paradoxolophus,” meaning paradoxical crest), has a nose that is roughly 9 millimeters in length.

“The typical horseshoe bat’s nose is half that long,” said Rolf Mueller, an associate professor with the Virginia Tech mechanical engineering department and director for the Bio-inspired Technology (BIT) Laboratory in Danville, Virginia.

“This nose is so much larger than anything else,” among other bats of the region, he said.

Mueller’s findings show that the bat uses its elongated nose to create a highly focused sonar beam.

Bats detect their environment through ultrasonic beams, or sonar, emitted from their mouths – or noses, as in the case of the paradoxolophus bat.

The echoes of the sound wave convey a wealth of information on objects in the bat’s environment.

Much like a flashlight with an adjuster that can create an intense but small beam of light, the bat’s nose can create a small but intense sonar beam.

Mueller and his team used computer animation to compare varying sizes of bat noses, from small noses on other bats to the large nose of the paradoxolophus bat.

In what Mueller calls a perfect mark of evolution, he says his computer modeling shows the length of the paradoxolophus bat’s nose stops at the exact point the sonar beam’s focal point would become ineffective.

“By predicting the width of the ultrasonic beam for each of these nose lengths with a computational method, we found that the natural nose length has a special value: All shortened noses provided less focus of the ultrasonic beam, whereas artificially elongated noses provided only negligible additional benefits,” Mueller said.

“Hence, this unusual case of a biological shape can be predicted accurately from its physical function alone,” he added. (ANI)

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Humans can develop echolocation like dolphins and bats

July 1, 2009 By Leave a Comment

Washington, July 1 (ANI): In a new research, scientists have shown that human beings can develop echolocation, the system of acoustic signals used by dolphins and bats to explore their surroundings.

The research was conducted by a team of researchers from the University of Alcala de Henares (UAH) in Spain.

“In certain circumstances, we humans could rival bats in our echolocation or biosonar capacity”, said Juan Antonio Martínez, lead author of the study and a researcher at the Superior Polytechnic School of the UAH.

The team led by this scientist has started a series of tests, the first of their kind in the world, to make use of human beings’ under-exploited echolocation skills.

In the first study, the team analyses the physical properties of various sounds, and proposes the most effective of these for use in echolocation.

“The almost ideal sound is the palate click, a click made by placing the tip of the tongue on the palate, just behind the teeth, and moving it quickly backwards, although it is often done downwards, which is wrong,” Martinez explained.

According to the researcher, palate clicks “are very similar to the sounds made by dolphins, although on a different scale, as these animals have specially-adapted organs and can produce 200 clicks per second, while we can only produce three or four”.

By using echolocation, “which is three-dimensional, and makes it possible to ‘see’ through materials that are opaque to visible radiation,” it is possible to measure the distance of an object based on the time that elapses between the emission of a sound wave and an echo being received of this wave as it is reflected from the object.

In order to learn how to emit, receive and interpret sounds, the scientists are developing a method that uses a series of protocols.

This first step is for the individual to know how to make and identify his or her own sounds (they are different for each person), and later to know how to use them to distinguish between objects according to their geometrical properties.

The next level is to learn how to master the “palate clicks”.

According to Martinez, his team is now working to help deaf and blind people to use this method in the future, because echoes are not only perceived by their ear, but also through vibrations in the tongue and bones.

A better understanding of the mental mechanisms used in echolocation could also help to design new medical imaging technologies or scanners, which make use of the great penetration capacity of clicks. (ANI)

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