Showing posts with label fourier transform. Show all posts
Showing posts with label fourier transform. Show all posts

Monday, June 30, 2014

Study helps unlock mystery of high-temp superconductors

Study helps unlock mystery of high-temp superconductors: "Evidence has been accumulating that this phase supports an exotic density wave state that may be key to its existence...". A density wave forms in a metal if the fluid electrons themselves crystalize.
Using a scanning tunneling microscope (STM) to visualize the electronic structure of the oxygen sites within a superconductor, the team found a density wave with a d-orbital structure. (The electron density near each copper atom looks a bit like a daisy in the crystallized pattern.) That's especially surprising because most density waves have an s-orbital structure; their electron density is isotropic. "It's not the pattern you would expect," Lawler says.
In this research, Lawler and his colleagues focused on a member of the cuprate class of superconductors called bismuth strontium calcium copper oxide (BSCCO). "We now believe these density waves exist in all cuprates," says Lawler, a theorist whose contribution to the research involved subtle uses of the Fourier transform, a mathematical analysis that's useful when examining amplitude patterns in waves.

Thursday, August 15, 2013

One-of-a-kind spectrometer reads vibrations between atoms to find structures of molecules

One-of-a-kind spectrometer reads vibrations between atoms to find structures of molecules:

By measuring the vibrations between atoms using femtosecond-long laser pulses, the Rice lab of chemist Junrong Zheng is able to discern the positions of atoms within molecules without the restrictions imposed by X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) imaging.
The technique can capture the structure of molecules at room temperature or very low or high temperatures and in many kinds of samples...

 "The atoms in every molecule are always vibrating, and each bond between atoms vibrates at a certain frequency, and in a certain direction," he said. "We found that if we can measure the direction of one vibration and then another, then we can know the angle between these two vibrations – and therefore the angle between the bonds."
He said the researchers begin with the chemical formula and already know, through Fourier transform infrared spectroscopy, how many vibrational frequencies are contained in a given molecule. "Then we measure each vibrational mode, one by one. Once we get all the cross-angles, we can translate this to a model," he said.

Wednesday, February 6, 2013

Musical brains smash audio algorithm limits - New Scientist - New Scientist

Musical brains smash audio algorithm limits: ...To investigate, Jacob Oppenheim and Marcelo Magnasco of Rockefeller University in New York turned to the Gabor limit, a part of the Fourier transform's mathematics that makes the determination of pitch and timing a trade-off...

The pair reasoned that if people's hearing obeyed the Gabor limit, this would be a sign that they were using the Fourier transform. But when 12 musicians, some instrumentalists, some conductors, took a series of tests, such as judging slight changes in the pitch and duration of sounds at the same time, they beat the limit by up to a factor of 13.

Monday, May 7, 2012

Faster fourier transform named one of world’s most important emerging technologies - MIT News Office

Faster fourier transform named one of world’s most important emerging technologies - MIT News Office: Their new algorithm, called the sparse Fourier transform (SFT), has been named to MIT Technology Review’s 2012 list of the world’s 10 most important emerging technologies.

With the SFT algorithm, streams of data can be processed 10 to 100 times faster than was possible before, allowing for a speedier and more efficient digital world.