January 3, 2008, 9:35 PM CT

Shape-memory polymers designed

Researchers at the Georgia Institute of Technology are developing unique polymers, which change shape upon heating, to open blocked arteries, probe neurons in the brain and engineer a tougher spine.

These so-called shape-memory polymers can be temporarily stretched or compressed into forms several times larger or smaller than their final shape. Then heat, light or the local chemical environment triggers a transformation into their permanent shape.

My focus has been to optimize these polymers for many different biomedical applications. My lab studies how altering the chemistry and structure of the polymers affects their chemical, biological and mechanical properties, said Ken Gall, a professor in the George W. Woodruff School of Mechanical Engineering and School of Materials Science and Engineering.

The mechanical properties of these polymers make them extremely attractive for many biomedical applications, according to Gall, who described his research in this area during two presentations at the Materials Research Societys fall meeting in November.

Engineers are always searching for materials that display unconventional properties able to satisfy the severe requirements for implantation in the body. Particular attention must be paid to the biofunctionality, biostability and biocompatibility of these materials, which come into contact with tissue and body fluids......... Posted by: Kevin      Read more         Source

January 3, 2008, 9:33 PM CT

North Atlantic warming tied to natural variability

A Duke University-led analysis of available records shows that while the North Atlantic Oceans surface waters warmed in the 50 years between 1950 and 2000, the change was not uniform. In fact, the subpolar regions cooled at the same time that subtropical and tropical waters warmed.

This striking pattern can be explained largely by the influence of a natural and cyclical wind circulation pattern called the North Atlantic Oscillation (NAO), wrote authors of a study published Thursday, Jan. 3, in Science Express, the online edition of the journal Science.

Winds that power the NAO are driven by atmospheric pressure differences between areas around Iceland and the Azores. The winds have a tremendous impact on the underlying ocean, said Susan Lozier, a professor of physical oceanography at Dukes Nicholas School of the Environment and Earth Sciences who is the studys first author.

Other studies cited in the Science Express report suggest human-caused global warming may be affecting recent ocean heating trends. But Lozier and her coauthors found their data cant support that view for the North Atlantic. It is premature to conclusively attribute these regional patterns of heat gain to greenhouse warming, they wrote.

The take-home message is that the NAO produces strong natural variability, said Lozier in an interview. The simplistic view of global warming is that everything forward in time will warm uniformly. But this very strong natural variability is superimposed on human-caused warming. So scientists will need to unravel that natural variability to get at the part humans are responsible for......... Posted by: Tyler      Read more         Source

January 2, 2008, 10:50 PM CT

Wind Tunnel Key For 'Hypersonic Vehicles,'

By using the only wind tunnel capable of running quietly at "hypersonic" speeds, Purdue University engineers have conducted experiments to yield critical data for designing an advanced aircraft called the X-51A, powered by engines called scramjets.

The X-51A test vehicle is expected to evolve into missiles capable of flying at Mach 6 - or six times the speed of sound - enabling them to hit mobile "time-critical" targets.

Scramjets also may propel future military and civilian space planes.

The quiet wind tunnel operation is critical for collecting data to show precisely how air flows over a vehicle's surface in flight. No other wind tunnel runs quietly while conducting experiments in airstreams traveling at Mach 6, said Steven Schneider, an aerospace engineer and professor in Purdue's School of Aeronautics and Astronautics.

"A quiet wind tunnel yields more accurate data because it more closely simulates flight," he said.

Specifically, engineers need detailed information about how airflow changes from "laminar," or smooth, to turbulent as it speeds over an aircraft's surfaces. The information is essential to properly design vehicles that fly at hypersonic speeds, or faster than Mach 5, nearly 4,000 mph, Schneider said.

The X-51 project is led by the Air Force Research Laboratory and the Defense Advanced Research Projects Agency, and the vehicle is being built by Pratt & Whitney and the Boeing Co. Purdue engineers are part of a national team of scientists from government, academia and industry handling different aspects of the vehicle......... Posted by: Kevin      Read more         Source

January 2, 2008, 10:44 PM CT

Smaller is Stronger

As structures made of metal get smaller - as their dimensions approach the micrometer scale (millionths of a meter) or less - they get stronger. Researchers discovered this phenomenon 50 years ago while measuring the strength of tin "whiskers" a few micrometers in diameter and a few millimeters in length. A number of theories have been proposed to explain why smaller is stronger, but only recently has it become possible to see and record what's actually happening in tiny structures under stress.

Andrew Minor, of the Materials Sciences Division in the Department of Energy's Lawrence Berkeley National Laboratory, with colleagues from Hysitron Incorporated and the General Motors Research and Development Center, used the In Situ Microscope at the National Center for Electron Microscopy (NCEM) to record what happens when pillars of nickel with diameters between 150 and 400 nanometers (billionths of a meter) are compressed under a flat punch made of diamond. The transmission electron microscope is equipped so that samples can be stressed, measured, and videotaped while being observed under the electron beam.

"What controls the deformation of a metal object is the way that defects, called dislocations, move along planes in its crystal structure," Minor says. "The result of dislocation slip is plastic deformation. For example, bending a paper clip causes its trillions of dislocations per square centimeter to tangle up and multiply as they run into one another and slide along numerous slip planes." ......... Posted by: Kevin      Read more         Source

December 27, 2007, 9:05 AM CT

Housewives are more ecologically aware

Research carried out in the Department of Social Psychology and Methodology of Behaviour Sciences of the University of Granada has shown that the level of academic training is not correlation to the ecological awareness of people, despite the great proliferation of programs designed to educate and increase social awareness of the environment. Thus, as per research, housewives are more ecologically aware than university students, given they are more willing to recycle glass.

This research was carried out by doctor María del Carmen Aguilar Luzon under the direction of professor J. Miguel Ángel García Martínez. The environmental behaviour chosen for the study was the separating of glass from other garbage. In the study, a sample of 525 university students and 154 housewives was used. Existing differences between both groups are significant: housewives are more willing to separate glass from other garbage, have a more favourable attitude towards recycling, and have enough willpower to do it.

Less control.

However, the researcher points out that university students "have less control over glass recycling behaviour, given they perceive it as a series of barriers and limitations hard to overcome." The container being far from home and they having to make their way to it while carrying heavy bags full of glass, for example, is viewed as a difficulty for students, and not for housewives. In fact, housewives adopt environmentally friendly practices more often than students......... Posted by: Tyler      Read more         Source

December 20, 2007, 9:50 PM CT

Missing Link Between Whales and Four-Footed Ancestors

Researchers have discovered the missing link between whales and their four-footed ancestors. The result is reported in this week's issue of the journal Nature. The research is funded by the National Science Foundation (NSF).

Researchers since Darwin have known that whales are mammals whose ancestors walked on land. In the past 15 years, scientists led by Hans Thewissen of the Northeastern Ohio Universities Colleges of Medicine and Pharmacy (NEOUCOM) have identified a series of intermediate fossils documenting whale's dramatic evolutionary transition from land to sea.

But one step was missing: The identity of the land ancestors of whales.

Now Thewissen and his colleagues have discovered the skeleton of Indohyus, an approximately 48-million-year-old even-toed ungulate from the Kashmir region of India, as the closest known fossil relative of whales.

"The evolution of whales is a tale of the adaptation of a land-based mammal to increasingly aquatic environments," said H. Richard Lane, program director in NSF's Division of Earth Sciences. "This recent discovery provides us with a new understanding of this near-shore-dwelling, shallow-water ancestor".

Thewissen's team studied a layer of mudstone with hundreds of bones of Indohyus, a fox-sized mammal that looked something like a miniature deer. They report key similarities between whales and Indohyus in the skull and ear that show their close family relationship. They also explored how Indohyus lived and came up with some surprising results. They determined that the bones of the skeleton of Indohyus had a thick outside layer, much thicker than in other mammals of this size. This characteristic is often seen in mammals that are slow aquatic waders, such as the hippopotamus today......... Posted by: William      Read more         Source

December 20, 2007, 9:48 PM CT

Metal Foam Has a Good Memory

In the world of commercial materials, lighter and cheaper is commonly better, particularly when those attributes are coupled with superior strength and special properties, such as a material's ability to remember its original shape after it's been deformed by a physical or magnetic force.

A new class of materials known as "magnetic shape-memory foams" has been developed by two research teams headed by Peter Müllner at Boise State University and David Dunand at Northwestern University, both funded by the National Science Foundation (NSF).

The foam consists of a nickel-manganese-gallium alloy whose structure resembles a piece of Swiss cheese with small voids of space between thin, curvy "struts" of material. The struts have a bamboo-like grain structure that can lengthen, or strain, up to 10 percent when a magnetic field is applied. Strain is the degree to which a material deforms under load. In this instance, the force came from a magnetic field rather a physical load. Force from magnetic fields can be exerted over long range, making them advantageous for a number of applications. The alloy material retains its new shape when the field is turned off, but the magnetically sensitive atomic structure returns to its original structure if the field is rotated 90 degrees--a phenomenon called "magnetic shape-memory"......... Posted by: Kevin      Read more         Source

December 20, 2007, 9:27 PM CT

The Quest for a New Class of Superconductors

Fifty years after the Nobel-prize winning explanation of how superconductors work, a research team from Los Alamos National Laboratory, the University of Edinburgh, and Cambridge University are suggesting another mechanism for the still-mysterious phenomenon.

In a review published recently in Nature, scientists David Pines, Philippe Monthoux and Gilbert Lonzarich posit that superconductivity in certain materials can be achieved absent the interaction of electrons with vibrational motion of a material's structure.

The review, "Superconductivity without phonons," explores how materials, under certain conditions, can become superconductors in a non-traditional way. Superconductivity is a phenomenon by which materials conduct electricity without resistance, commonly at extremely cold temperatures around minus 424 degrees Fahrenheit (minus 253 degrees Celsius)-the fantastically frigid point at which hydrogen becomes a liquid. Superconductivity was first discovered in 1911.

A newer class of materials that become superconductors at temperatures closer to the temperature of liquid nitrogen-minus 321 degrees Fahrenheit (minus 196 degrees Celsius)-are known as "high-temperature superconductors".

A theory for conventional low-temperature superconductors that was based on an effective attractive interaction between electrons was developed in 1957 by John Bardeen, Leon Cooper and John Schrieffer. The explanation, often called the BCS Theory, earned the trio the Nobel Prize in Physics in 1972......... Posted by: Kevin      Read more         Source

December 20, 2007, 9:23 PM CT

El Nio affected by global warming

The climatic event El Nio, literally the Baby Jesus, was given its name because it generally occurs at Christmas time along the Peruvian coasts. This expression of climatic variability, also called El Nio Southern Oscillation (ENSO), results from a series of interactions between the atmosphere and the tropical ocean. It induces drought in areas that normally receive abundant rain and, on the other hand, heavy rainfall and floods in commonly arid desert zones. Researchers term this phenomenon a quasi-cyclic variation because its periodicity, which varies from 2 to 7 years, shows no regular time pattern. Research conducted over the past 25 years, by oceanographers, climatologists and meteorologists has much improved knowledge on the mechanisms generating an El Nio event. However, possible influence of other systems of climate variability on the ENSO regime is more difficult to fathom. More particularly, it is not known if the intensity and frequency of the event is susceptible to modification in a situation of global warming.

The research work recently published by a team of Chilean and IRD researchers sheds new light on El Nios variability. Several geochemical factors contained in a drill core sediment sampled from 80 m depth under the Bay of Mejillones, in northern Chile, were determined. Analysis of breakdown byproducts from diatoms, unicellular planktonic algae, yielded an accurate trace of this regions trends in sea surface temperature between 1650 and 2000. Data for the period 1820-1878 showed a fall of over 2C. This temperature decrease was also detected in two cores collected near the South-American coasts, over 1000 km to the North and South of Mejillones......... Posted by: Tyler      Read more         Source

December 20, 2007, 9:15 PM CT

Greenhouse gases and the evolution of C4 grasses

How a changing climate can affect ecosystems is an important and timely question, particularly considering the recent global rise in greenhouse gases. Now, in an article published online on December 20th in the journal Current Biology, evolutionary biologists provide good evidence that changes in global carbon dioxide levels probably had an important influence on the emergence of a specific group of plants, termed C4 grasses, which includes major cereal crops, plants used for biofuels, and species that represent important components of grasslands across the world.

C4 plants are specially equipped to combat an energetically costly process, known as photorespiration, that can occur under conditions of high temperature, drought, high salinity, andith relevance to these latest findingslow carbon dioxide levels. Eventhough a combination of any of these factors might have provided the impetus behind the evolution of the various C4 lineages, it had been widely speculated that a drop in global carbon dioxide levels, occurring approximately 30 million years ago during the Oligocene period, may have been the major driving force. Establishing the link between the two, however, has proven difficult partly because there are no known fossils of C4 plants from this period. Enter Pascal-Antoine Christin and his colleagues from the University of Lausanne, Switzerland, who decided to take an alternative approach to date a large group of grasses. By using a molecular clock technique, the authors were able to determine that the Chloridoideae subfamily of grasses emerged approximately 30 million years ago, right around the time global carbon dioxide levels were dropping. Furthermore, a model of the evolution of these grasses suggests that this correlation is not a trivial coincidence and instead reflects a causal relationship......... Posted by: Tyler      Read more         Source