More physics faculty land papers in Nature pubs

Valerica Raicu

In the last two years, five UWM physics professors have had articles published in Nature journals, an indicator of the department’s high productivity. The five include Abbas Ourmazd, Dilano Saldin, Valerica Raicu, Daniel Agterberg and Prasenjit Guptasarma. The articles appeared in Nature Physics or Nature Photonics.

In addition to the paper co-authored with Ourmazd and Saldin described in “Picturing Unruly Proteins,” another professor has published research on a novel way to “see” and study proteins, which carry out most of the functions necessary for life.

Nature PhotonicsUsing a technique they developed, members of Assistant Professor Valerica Raicu’s lab have become the first group of scientists to determine the structure of a protein complex with molecular resolution in a living cell.

Proteins carry out most functions in our bodies that are essential for life. They often work in combination, called a “complex,” but their structures have been impossible to image with current methods.

The group uses a tightly focused laser to view the distribution of proteins and their complexes inside a cell. Then they image a special transfer of energy that occurs when molecules excited by a laser come within a nanometer of each other. This allows the researchers to get single “snapshots” of proteins working together.

The work could be an important tool in the discovery of new drugs as well as for understanding the molecular basis of disease.

http://www.nature.com/nphoton/journal/v3/n2/full/nphoton.2008.291.html

Nature PhysicsTwo other papers address the behavior of materials that can superconduct at relatively high temperatures.

Daniel Agterberg

In materials that superconduct, electric current flows through with no friction, creating an enormous saving in energy. Superconductors are key to developing new energy-related technologies and the next generation of lightning-speed computers and smart electronics. Unfortunately, most materials that superconduct can only do so at temperatures close to absolute zero (-460 degrees F), making them economically unfeasible.

In the 1980s, scientists discovered materials that can superconduct at higher temperatures (around -320 degrees F), but how these materials work is still unknown. Before this kind of superconductivity can be used widely, scientists must first understand the phenomenon.

Professor Daniel Agterberg and his co-author, H. Tsunetsugu at the University of Tokyo, have explored a new category of superconductors and found they contain a new class of vortices. Resembling tiny tornadoes, vortices play an important role in understanding high-temperature superconductors.

Vortices in a superconducting material

The discovery of a new class of vortices could lead to a series of new insights that may prove central to solving the mystery of high-temperature superconductors, says Agterberg.

Only two families of high-temperature superconducting materials are currently known.
“It would be beneficial to know more about these materials,” he says, “so we may be able to figure out how to engineer others.”

http://www.nature.com/nphys/journal/v4/n8/abs/nphys999.html

Prasenjit Guptasarma

Associate Professor Prasenjit Guptasarma’s paper in Nature Physics also addresses the behavior of vortices in high-temperature superconductors.

Superconductivity in these materials is destroyed in a high magnetic field because vortices are unstable. Those vortices must be stabilized to avoid loss of superconductivity.

Guptasarma and his collaborator Bill Halperin of Northwestern University have shown that, in single crystals of the material they tested, called BSCCO, superconductivity can exist even in a very high magnetic field.

The reason, he says, is the vortices change from an unstable three-dimensional state to a stable two-dimensional state with a change in the temperature.

Because of the purity of the BSCCO crystals, the researchers were able to observe this change in states that had not been recorded by others.

This discovery has implications for use in high field magnetism such as those used in medical MRI.

http://www.nature.com/nphys/journal/v3/n4/abs/nphys540.html