Syracuse University chemist develops technique to use light to predict molecular crystal structures
|March 23rd, 2011|
|A Syracuse University chemist has developed a way to use very low frequency light waves to study the weak forces (London dispersion forces) that hold molecules together in a crystal. This fundamental research could be applied to solve critical problems in drug research, manufacturing and quality control.|
The research by Timothy Korter, associate professor of chemistry in SU's College of Arts and Sciences, was the cover article of the March 14 issue of Physical Chemistry Chemical Physics. The journal, published by the Royal Society of Chemistry, is one of the most prestigious in the field. A National Science Foundation Early Career Development (CAREER) Award funds Korter's research.
"When developing a drug, it is important that we uncover all of the possible ways the molecules can pack together to form a crystal," Korter says. "Changes in the crystal structure can change the way the drug is absorbed and accessed by the body."
One industry example is that of a drug distributed in the form of a gel capsule that crystallized into a solid when left on the shelf for an extended period of time, Korter explains. The medication inside the capsule changed to a form that could not dissolve in the human body, rendering it useless. The drug was removed from shelves. This example shows that it is not always possible for drug companies to identify all the variations of a drug's crystal structure through traditional experimentation, which is time consuming and expensive.
"The question is," Korter says, "can we leverage a better understanding of London and other weak intermolecular forces to predict these changes in crystal structure?"
Korter's lab is one of only a handful of university-based research labs in the world exploring the potential of THz radiation for chemical and pharmaceutical applications. THz light waves exist in the region between infrared radiation and microwaves and offer the unique advantages of being non-harmful to people and able to safely pass through many kinds of materials. THz can also be used to identify the chemical signatures of a wide range of substances. Korter has used THz to identify the chemical of signatures of molecules ranging from improvised explosives and drug components to the building blocks of DNA.
Korter's new research combines THz experiments with new computational models that accurately account for the effects of the London dispersion forces to predict crystal structures of various substances. London forces are one of several types of intermolecular forces that cause molecules to stick together and form solids. Environmental changes (temperature, humidity, light) impact the forces in ways that can cause the crystal structure to change. Korter's research team compares the computer models with the THz experiments and uses the results to refine and improve the theoretical models.
"We have demonstrated how to use THz to directly visualize these chemical interactions," Korter says. "The ultimate goal is to use these THz signatures to develop theoretical models that take into account the role of these weak forces to predict the crystal structures of pharmaceuticals before they are identified through experimentation."
Source: Syracuse University
Thursday, March 24, 2011
Saturday, March 5, 2011
Invisibility cloaks may be just around the corner
In 1897, H.G. Wells created a fictional scientist who became invisible by changing his refractive index to that of air, so that his body could not absorb or reflect light. More recently, Harry Potter disappeared from sight after wrapping himself in a cloak spun from the pelts of magical herbivores.
Countless other fictional characters in books and films throughout history have discovered or devised ways to become invisible, a theme that long has been a staple of science fiction and a source of endless fascination for humans. Who among us has never imagined the possibilities? But, of course, it's not for real.
Or is it?
While no one yet has the power to put on a garment and disappear, Elena Semouchkina, an associate professor of electrical and computer engineering at Michigan Technological University, has found ways to use magnetic resonance to capture rays of visible light and route them around objects, rendering those objects invisible to the human eye. Her work is based on the transformation optics approaches, developed and applied to the solution of invisibility problems by British scientists John B. Pendry and Ulf Leonhardt in 2006.
"Imagine that you look at the object, which is placed in front of a light source," she explains.
"The object would be invisible for your eye if the light rays are sent around the object to avoid scattering, and are accelerated along these curved paths to reach your eye undistinguishable from direct straight beams exiting the source, when the object is absent."
At its simplest, the beams of light flow around the object and then meet again on the other side so that someone looking directly at the object would not be able to see it--but only what's on the other side.
"You would see the light source directly through the object," said Semouchkina. "This effect could be achieved if we surround the object by a shell with a specific distribution of such material parameters as permittivity and permeability."
She and her collaborators at the Pennsylvania State University, where she is also an adjunct professor, designed a nonmetallic "invisibility cloak" that uses concentric arrays of identical glass resonators made of chalcogenide glass, a type of dielectric material--that is, one that does not conduct electricity.
In computer simulations, the cloak made objects hit by infrared waves--approximately one micron, or one-millionth of a meter long--disappear from view.
The potential practical applications of the work could be dramatic, for example, in the military, such as "making objects invisible to radar," she said, as well as in intelligence operations "to conceal people or objects."
Furthermore, "shielding objects from electromagnetic irradiation is also very important," she said, adding, "for sure, the gaming industry could use it in new types of toys."
Multi-resonator structures comprising Semouchkina's invisibility cloak belong to "metamaterials"--artificial materials with properties that do not exist in nature--since they can refract light by unusual ways. In particular, the "spokes" of tiny glass resonators accelerate light waves around the object making it invisible.
Until recently, there were no materials available with the relative permeability values between zero and one, which are necessary for the invisibility cloak to bend and accelerate light beams, she said. However, metamaterials, which were predicted more than 40 years ago by the Russian scientist Victor Veselago, and first implemented in 2000 by Pendry from Imperial College, London, in collaboration with David R. Smith from Duke University, now make it possible, she said.
Metamaterials use lattices of resonators, instead of atoms or molecules of natural materials, and provide for a broad range of relative permittivity and permeability including zero and negative values in the vicinity of the resonance frequency, she said. Metamaterials were listed as one of the top three physics discoveries of the decade by the American Physical Society.
"Metamaterials were initially made of metallic split ring resonators and wire arrays that limited both their isotropy (uniformity in all directions) and frequency range," Semouchkina said. "Depending on the size of split ring resonators, they could operate basically at microwaves and millimeter (mm) waves."
In 2004, her research group proposed replacing metal resonators with dielectric resonators. "Although it seemed strange to control magnetic properties of a metamateral by using dielectrics, we have shown that arrays of dielectric resonators can provide for negative refraction and other unique properties of metamaterials," she said. "Low loss dielectric resonators promise to extend applications of metamaterials to the optical range, and we have demonstrated this opportunity by designing an infrared cloak."
Semouchkina and colleagues recently reported on their research in the journalApplied Physics Letters, published by the American Institute of Physics. Her co-authors were Douglas Werner and Carlo Pantano of Penn State and George Semouchkin, who teaches at Michigan Tech and has an adjunct position with Penn State.
The National Science Foundation (NSF) is funding her research on dielectric metamaterials and the team's applications with a $318,520 award, but she plans to apply for an additional grant to conduct specific studies into invisibility cloak structures.
Semouchkina, who received her master's degree in electrical engineering and her doctorate in physics and mathematics from Tomsk State University in her native Russia, has lived in the United States for 13 years, and has been a U.S. citizen since 2005. She also earned her second doctorate in materials in 2001 from Penn State.
She and her team now are testing an all-dielectric invisibility cloak rescaled to work at microwave frequencies, performing experiments in Michigan Tech's anechoic chamber, a cave-like compartment in an electrical energy resources center lab, lined with highly absorbent charcoal-gray foam cones.
There, "horn" antennas transmit and receive microwaves with wavelengths up to several centimeters, that is, more than 10,000 times longer than in the infrared range. They are cloaking metal cylinders two to three inches in diameter and three to four inches high with a shell comprised of mm-sized ceramic resonators, she said.
"We want to move experiments to higher frequencies and smaller wavelengths," she said, adding: "The most exciting applications will be at the frequencies of visible light."
Provided by National Science Foundation
Tuesday, March 1, 2011
WHAT IS THE STATUS OF MALAYSIA ENERGY SECURITY?
The energy industry's face challenges and need solutions for protecting critical assets including oil and gas infrastructure, transmission grids, power plants, storage, pipelines, and all aspects of strategic industry assets. Of special concern is the new Cyber-terrorism and protecting Control Systems.
Recent terrorist activities like the China hacker attack on global oil and gas companies - as reported by security company McAfee, have raised several critical questions:
- How can the Malaysia defend itself against future attacks on critical infrastructure such as energy systems?
- Are energy supplies vulnerable to attack, and if so ? how and where?
- How can energy generating and storage facilities be made safer?
- How can we protect transportation systems and transmission lines?
- How are government and industry leaders working together to develop contingency plans to protect the public?
- What policies would enhance Malaysia energy security?
- What are the roles of industry and government?
Energy security is a complex, multi-faceted issue. In its most fundamental sense, energy security is assured when a nation can deliver energy economically, reliably, in an environmentally sound and safe manner, and in quantities sufficient to support its economic and defense needs. To do this requires policies that support expansion of all elements of the energy supply and delivery infrastructure, with sufficient storage and generating reserves, diversity, and redundancy to meet the demands of economic growth.
The threats facing the nation's critical energy infrastructure continue to evolve and present new challenges. The intricate nature of the nation's electrical grid is becoming readily apparent with rolling blackouts and the potential for further disruptions. The interdependencies of the oil, natural gas, and electric infrastructures are increasingly complex and not easily understood. The impact of a major terrorist attack directed against this fragile and interdependent infrastructure could have drastic consequences.
Conflict over resources stretches far back in human history, and energy infrastructures have long been subject to planned attacks. For instance, the New World Liberation Front bombed assets of the Pacific Gas & Electric Company over 10 times in 1975 alone. Members of the Ku Klux Klan and San Joaquin Militia were convicted of conspiring or trying to attack energy infrastructure. Organized paramilitaries have had significant impacts in some countries. For example, the Farabundo-Marti National Liberation Front interrupted service in up to 90% of El Salvador at a time and created manuals for attacking power systems.
So what is the current state of the industry, and is there is a serious effort to provide insights on all aspects of infrastructure and asset protection and recovery being done?
Adapted from EnergyBusinessReports