Superconductivity has perplexed, astounded and inspired scientists ever since it was discovered in 1911. Now, in the latest of a century of surprises, researchers at the National High Magnetic Field Laboratory at Florida State University have discovered unusual properties in a novel superconducting material that point to an entirely new kind of superconductor.

Frank Hunte, a postdoctoral associate at the lab’s Applied Superconductivity Center (ASC), working with David Larbalestier, Alex Gurevich and Jan Jaroszynski, and colleagues in David Mandrus’ group at Oak Ridge National Laboratory in Tennessee, discovered surprising magnetic properties in the new superconductors that suggest they may have very powerful applications — from improved MRI machines and research magnets to a new generation of superconducting electric motors, generators and power transmission lines. The research also adds to the long list of mysteries surrounding superconductivity, providing evidence that the new materials, which scientists are calling “doped rare earth iron oxyarsenides,” develop superconductivity in quite a new way, as detailed recently in the journal Nature.

Though research on this substance is very much in its early stages, scientists are talking excitedly of “promise” and “potential.”

“What one would like is a greater selection of superconductors, operating at higher temperatures, being cheaper, possibly being more capable of being made into round wires,” said Larbalestier, director of the ASC. “Iron and arsenic, both inherently cheap materials, are key constituents of this totally new class of superconductors. We’re just fascinated. It’s superconductivity in places you never thought of.”

Superconductivity can be thought of as “frictionless” electricity. In conventional electricity, heat is generated by friction as electrons (electric charge carriers) collide with atoms and impurities in the wire. This heating effect is good for appliances such as toasters or irons, but not so good for most other applications that use electricity. In superconductors, however, electrons glide unimpeded between atoms without friction. If scientists and engineers ever harness this phenomenon at or near room temperature in a practical way, untold billions of dollars could be saved on energy costs.

That’s a big if. Superconductivity, though promising, is still impractical in routine engineering use because it requires a very cold environment attainable only with the help of expensive cryogens such as liquid helium or liquid nitrogen. Past discoveries have helped scientists inch their way up the thermometer, from superconductors requiring minus 452 degrees Fahrenheit (or 4.2 Kelvin) to newer materials that superconduct at around minus 200 degrees F (138 K) — still frigid, but substantially warmer and more practical.

Early this year, Japanese scientists who had been developing iron-based superconducting compounds for several years finally tweaked the recipe just right with a pinch of arsenic. The result: a superconductor, also featuring oxygen and the rare earth element lanthanum, performing at a promising minus 413 degrees F (26 K). The presence of iron in the material was another scientific stunner: Because it’s ferromagnetic, iron stays magnetized after exposure to a magnetic field, and any current generates such a field. As a rule, magnetism’s effect on superconductivity is not to enhance it, but to kill it.

Teams of scientists quickly got busy synthesizing and studying various iron oxyarsenides. Larbalestier, eager to get in on the research, secured a sample from colleagues at Oak Ridge. His objective: Put it in the magnet lab’s 45-tesla Hybrid magnet to see how high a magnetic field the new material could tolerate. (Tesla is a unit of magnetic field strength; the Earth’s magnetic field is one twenty thousandth of a tesla.)

Hunte and his colleagues thought the world-record Hybrid magnet would be more than sufficient to test the field tolerance limits of the new material. They thought wrong: The iron oxyarsenide kept superconducting all the way up to 45 tesla, far past the point at which other superconductors become normal conductors.

A high tolerance for magnetic field is one of three key properties researchers hope for in superconductors. Also desirable are the abilities to operate at relatively high temperatures and in the presence of high electrical currents. Superconductors are used to make MRI and research magnets, and now they are being tested in a new generation of superconducting electric motors, generators, transformers and power transmission lines. Today, the most powerful superconducting magnet generates a field of about 26 tesla. If a superconductor could be found that tolerates a higher current and field, it may make possible more powerful magnets, opening up vast new research areas to scientists and power applications.

Hunte’s experiment yielded other tantalizing findings. Although scientists discovered half a century ago that superconducting electrons enter the “Cooper pair” state, pairing with opposite spin and momentum, magnetism was always thought to break such pairs. Now the archetypal magnetic atom, iron, is a key part of this new class of high temperature superconductors. Scientists have yet another puzzle to probe.

“So far,” said Hunte, “based on both theoretical calculations and what we’re seeing from the experiments, it seems likely that this is a completely different mechanism for superconductivity.”

Hunte is quick to say the group’s research barely scratches the surface.

“The field is completely open. No one knows where this is going to go,” Hunte said. “If it’s found that these materials can support high current densities, then they could be tremendously useful.”

Source

The announcement of the discovery of a new bird comes with a twist: It’s a white-eye, but its eye isn’t white. Still, what this new bird lacks in literal qualities it makes up for as one of the surprises that nature still has tucked away in little-explored corners of the world.

Ornithologists, including one from Michigan State University, describe for science a new species of bird from the Togian Islands of Indonesia – Zosterops somadikartai, or Togian white-eye, in the March edition of The Wilson Journal of Ornithology.

Its eye isn’t ringed in a band of white feathers like its cousins who flock in other remote tropical islands of Indonesia. Still, it has many features in common with the black-crowned white-eye Zosterops atrifrons of Sulawesi, which is clearly its closest relative, said MSU’s Pamela Rasmussen, an internationally known ornithologist specializing in Asian birds.

“What this discovery highlights is that in some parts of the world there are still virtually unexplored islands where few ornithologists have worked,” Rasmussen said. “The world still holds avian surprises for us.”

The Togian white-eye first was spotted by Mochaamad Indrawan, an Indonesian field biologist at the Depok Campus of the University of Indonesia, and Sunarto (some Indonesians use a single name), who is now working on a doctorate at Virginia Tech, 12 years ago during their first trip to the Togian Islands.

Those first sightings were fleeting, but Indrawan and Sunarto returned and made several more observations of these active little green birds, and obtained the type specimen upon which the species’ description is now founded. The type specimen was then sent on loan to Rasmussen at the MSU Museum, so she could make detailed comparisons between it and related species at museums such as Britain’s Natural History Museum, the American Museum in New York and the Smithsonian Institution.

The new bird is believed to be endangered. The white-eye has been seen only near the coasts of three small islands of the Togian Islands in central Sulawesi. Unlike most white-eye species, it is evidently quite uncommon even in its very limited range. Considering its limited numbers and distribution, it falls into the World Conservation Union category of endangered. This finding also establishes the Togian Islands as an endemic bird area.

“This finding shows that equal opportunities are beneficial for the development of science and in particular that international cooperation can boost capacities in addressing poorly known biology in the tropics,” Indrawan said. “This finding of the bird is only the beginning given the vast opportunities with Indonesian landscapes and seascapes of endemic flora and fauna.”

The species is named for Soekarja Somadikarta, Indonesia’s leading taxonomist and mentor to Indrawan. Somadikarta was recently appointed honorary president for International Ornithological Congress XXV.

Rasmussen noted that the Togian white-eye is distinctive not only in appearance, but its lilting song, which Indrawan recorded and Rasmussen committed to sonogram, sounds higher pitched and is less varied in pitch than its close relatives.

Source

Helicobacter pylori is one tough bug. It can survive in the human stomach, a zone with a pH somewhere between that of lemon juice and battery acid. Now researchers have discovered how an H. pylori toxin gets into cells, a feat that helps the bacterium live in one of the most inhospitable environments in the body.

About half of the world’s population is infected with H. pylori, although most of them don’t know it (most infected people have no obvious symptoms). For a percentage of the infected, however, the bacterium packs a nasty punch. H. pylori is responsible for most human cases of gastric and duodenal ulcers, and long-term infection is a significant risk factor for stomach cancer, the second leading cause of cancer death worldwide.

Researchers have tried for years to understand how the bacterium survives in the human stomach, said Steven Blanke, a University of Illinois professor in the department of microbiology and Institute for Genomic Biology and principal investigator on the study.

“Paradoxically, although H. pylori is a common resident of the human stomach, the bug is not well adapted by itself to acid,” he said. “But this pathogen has several clever mechanisms for carving out a niche for itself in the stomach lining.”

A protein produced by H. pylori, called vacuolating toxin A (VacA), is an important weapon in its arsenal.

“This toxin gets into stomach epithelial cells and immune cells and changes their properties in such a way as to allow H. pylori to first gain a foothold in the stomach, and then survive over the long-term, which may be the entire lifetime of an individual,” Blanke said.

“H. pylori releases the VacA toxin in order to modify its environment,” he said.

How the toxin crossed the membrane to get into these cells was a mystery, however.

Cell membranes are composed primarily of lipids and proteins and are designed to keep things out. Some molecules can penetrate them, but most can do so only after binding to a specific membrane component, called a receptor. Receptors sometimes act as keys that open channels through a membrane, or they function as signaling molecules, communicating to other components in the cell.

Blanke’s team knew that VacA was latching on to something on the cell surface that was helping it across the membrane.

Other studies had shown that VacA bound to lipids within artificially created membranes, so graduate students Vijay Gupta and Hetal Patel screened a number of lipids for VacA binding and soon found one to which the toxin readily attached. This lipid, called sphingomyelin, is an important and abundant component of the membrane of some animal cells. (Foods such as milk, meat, fish and eggs are dietary sources of sphingomyelin.)

To be considered a receptor, a molecule must meet two criteria, Blanke said. It must bind the agent of interest (in this case VacA) to the cell surface, and it must “confer sensitivity” to that agent. In other words, a receptor to VacA must be essential to the process by which VacA gets into a cell. If you removed the receptor, or blocked it, the toxin would lose its ability to bind or function. Prior to this study, no molecules on the membrane of human cells had been found that satisfied both criteria as a receptor.

Upon entering cells, VacA spurs the formation of giant vacuoles. These oversized membrane-bound compartments are easy to spot under a microscope and provide a useful indicator of VacA activity in the cell.

To test whether sphingomyelin was a receptor for VacA, Gupta treated cultured human cells with an enzyme that depleted the membranes of sphingomyelin. In the sphingomyelin-depleted cells, the toxin lost its ability to cross into the cells and the giant vacuoles disappeared. When he restored sphingomyelin to the same cell membranes (again, in the presence of VacA), the vacuoles returned.

“This is the first example of a bacterial virulence factor that uses sphingomyelin as a receptor,” Blanke said. “Only sphingomyelin confers sensitivity to the toxin in these cells, whereas other common membrane lipids do not.”

Sphingomyelin recently was discovered to have the ability to cluster into specialized membrane islands, or rafts, that look like raised platforms on the cell surface.

Blanke’s team found that VacA preferentially binds to and enters the cell by means of these sphingomyelin rafts.

“Our model is that these platforms serve as the entry portals for the toxin into the cell,” Blanke said. “We think that sphingomyelin is important because it seems to cluster the toxin in these portals of entry. This seems to be absolutely essential for toxin activity.”

Finding the mechanism by which the toxin gets into cells is of great interest to those hoping to treat H. pylori infection, Blanke said.

“Identifying toxin receptors is important because they are outstanding targets for new drugs to block the action of toxins on human cells,” he said.

Also, because some bacterial toxins are so adept at breeching the membrane barrier to enter human cells, this work may also point the way to new strategies for sending protein-based pharmaceuticals into the cell, he said.

Their findings appeared recently in PLoS Pathogens, a journal of the Public Library of Science.

Source