When you hear the word "planet," do you automatically think of the word's literal definition, or of other words, such as "Earth," "space," "Mars," etc.? Especially when used in sentences, words tend to conjure up similar words automatically. Further, human beings' ability to draw associations and inferences between words may explain why we're generally able to communicate complex ideas with each other quite clearly using a limited number of words.
Research has shown that words are stored in our memories not as isolated entities but as part of a network of related words. This explains why seeing or hearing a word activates words related to it through prior experiences. In trying to understand these connections, scientists visualize a map of links among words called the mental lexicon that shows how words in a vocabulary are interconnected through other words.
However, it's not clear just how this word association network works. For instance, does word association spread like a wave through a fixed network, weakening with conceptual distance, as suggested by the "Spreading Activation" model? Or does a word activate every other associated word simultaneously, as suggested in a model called "Spooky Activation at a Distance"?
Science & Technology
© NASA
NASA's STEREO spacecraft will search for objects trapped at the Lagrangian points.
NASA's STEREO spacecraft will search for objects trapped at the Lagrangian points.
In the 4.5 billion years since the formation of the solar system, everything from dust clouds to asteroids and hidden planets may have accumulated there. Some have even speculated that alien spacecraft are watching us from the Lagrangian points, looking for signs of intelligence.
Putting little green men to one side for the moment, even the presence of plain old space rocks would be enough to keep most people happy. "I think you certainly might find a whole population of objects at L4 and L5," says astrophysicist Richard Gott of Princeton University.
© Charles H. Whitfield
The famous stone sculptures on Easter Island where Dr. Stevenson and Rapanui scientist Sonia Haoa have worked with Earthwatch volunteers for the last 20 years to uncover new twists in the story of Easter Island.
The famous stone sculptures on Easter Island where Dr. Stevenson and Rapanui scientist Sonia Haoa have worked with Earthwatch volunteers for the last 20 years to uncover new twists in the story of Easter Island.
Easter Island (Rapa Nui) has gained recognition in recent years due in part to a book that used it as a model for societal collapse from bad environmental practices - ringing alarm bells for those concerned about the health of the planet today. But that's not the whole story, says Dr. Chris Stevenson, an archaeologist who has studied the island - famous for its massive stone statues - with a Rapa Nui scientist, Sonia Haoa, and Earthwatch volunteers for nearly 20 years.
The ancient Rapanui people did abuse their environment, but they were also developing sustainable practices - innovating, experimenting, trying to adapt to a risky environment - and they would still be here in traditional form if it weren't for the diseases introduced by European settlers in the 1800s.
"Societies don't just go into a tailspin and self-destruct," says Stevenson, an archaeologist at the Virginia Department of Historic Resources. "They can and do adapt, and they emerge in new ways. The key is to put more back into the system than is taken out."
© NASA
Now that definitely sounds like something Electra, Queen of the Lunar Amazon Women, would apply to Buck before being seduced. It's important not to get overexcited - here "negative anomaly" simply means that there's less gravity than average, not that there are anti-gravity sites hidden where we couldn't see them until now. These rings surround small zones of positive gravity anomalies, unlike anything we've seen on the near side, and offer brand new information on the formation of the moon.
The enormous pressures needed to melt diamond to slush and then to a completely liquid state have been determined ten times more accurately by Sandia National Laboratories researchers than ever before.
As a bonus to science, researchers Marcus Knudson, Mike Desjarlais, and Daniel Dolan discovered a triple point at which solid diamond, liquid carbon, and a long-theorised but never-before-confirmed state of solid carbon called bc8 were found to exist together.
Accurate knowledge of these changes of state are essential in simulating behaviours of celestial bodies, and to the effort to produce nuclear fusion at Lawrence Livermore National Laboratory's National Ignition Facility in California.
The changes resemble those undergone by ice as it melts into water, but under much more extreme conditions.
As a bonus to science, researchers Marcus Knudson, Mike Desjarlais, and Daniel Dolan discovered a triple point at which solid diamond, liquid carbon, and a long-theorised but never-before-confirmed state of solid carbon called bc8 were found to exist together.
Accurate knowledge of these changes of state are essential in simulating behaviours of celestial bodies, and to the effort to produce nuclear fusion at Lawrence Livermore National Laboratory's National Ignition Facility in California.
The changes resemble those undergone by ice as it melts into water, but under much more extreme conditions.
© Unknown
Responding to a deadly 1997 outbreak of the mosquito-borne disease Rift Valley fever, researchers had developed a "risk map," pictured above, using NASA and National Oceanic and Atmospheric Administration measurements of sea surface temperatures, precipitation, and vegetation cover. As reported in a recent NASA-led study, the map gave public health officials in East Africa up to six weeks of warning for the 2006-2007 outbreak of the deadly Rift Valley fever in northeast Africa - enough time to lessen human impact.
On the map above, pink areas depict increased disease risk, while pale green areas reflect normal risk. Yellow dots represent reported Rift Valley fever cases in high-risk areas, while blue dots represent occurrences in non-risk areas. The researchers have detailed the map's effectiveness in the Proceedings of the National Academy of Sciences.
Research scientists in Bonn, Germany, have succeeded in deriving so-called brain stem cells from human embryonic stem cells. These can not only be conserved almost indefinitely in culture, but can also serve as an inexhaustible source of diverse types of neural cell. The scientists have also shown that these neural cells are capable of synaptic integration in the brain. Their results have been published in the latest edition of the Proceedings of the National Academy of Sciences.
For years, stem cell research appeared to be divided between two worlds: on the one hand, were the embryonic stem cells - omnipotent, with unlimited development potential, and on the other, were the so-called somatic stem cells, which were obtainable from adult tissue, but have only limited potential for self-renewal and development. Scientists in Bonn have now succeeded in combining these two worlds: they have derived brain stem cells of almost unlimited self-renewal capacity and conservation potential from human embrionic stem cells. Using these stable cell lines, they were then able to obtain a continual in vitro supply of diverse types of human neural cell including, for example, those which fail with Parkinson´s disease.
For years, stem cell research appeared to be divided between two worlds: on the one hand, were the embryonic stem cells - omnipotent, with unlimited development potential, and on the other, were the so-called somatic stem cells, which were obtainable from adult tissue, but have only limited potential for self-renewal and development. Scientists in Bonn have now succeeded in combining these two worlds: they have derived brain stem cells of almost unlimited self-renewal capacity and conservation potential from human embrionic stem cells. Using these stable cell lines, they were then able to obtain a continual in vitro supply of diverse types of human neural cell including, for example, those which fail with Parkinson´s disease.
© Mark Witton
A new study published today in the journal PLoS ONE by researchers from Ohio University, College of the Holy Cross and the University of Leicester explains how balloon-like air sacs, which extended from the lungs to inside the skeleton of pterosaurs, provided an efficient breathing system for the ancient beasts. The system reduced the density of the body in pterosaurs, which in turn allowed for the evolution of the largest flying vertebrates.
"We offer a reconstruction of the breathing system in pterosaurs, one that proposes the existence of a mechanism with the same essential structure to that of modern birds - except 70 million years earlier," said study co-author Leon Claessens, an assistant professor of biology at the College of the Holy Cross.
© Wikimedia Commons
A picture of our galaxy's core, the Milky Way.
A picture of our galaxy's core, the Milky Way.
Gamma rays, the main emissions that have been recently recorded, are formed by an energy approximately one thousand times more powerful than X-rays, and represent only the visible light portion of that energy. They are triggered by antimatter and matter coming together, usually in the central portions of galaxies. In the Milky Way, they originate from the formation's central regions, located somewhere in the Southern hemisphere.
Evidence unearthed at more than two dozen sites across North America suggests that an extraterrestrial object exploded in Earth's atmosphere above Canada about 12,900 years ago, just as the climate was warming at the end of the last ice age. The explosion sparked immense wildfires, devastated North America's ecosystems and prehistoric cultures, and triggered a millennium-long cold spell, scientists say.
