Saturday, August 30, 2008

Louis J. Sheehan

http://louis-j-sheehan.info



Four days after suffering a brain-damaging stroke, a 73-year-old woman told her physicians of a startling development. In addition to experiencing mild vision problems sparked by the stroke, she had stopped dreaming.http://louis-j-sheehan.info

This woman offered researchers their first opportunity to explore the biology of Charcot-Wilbrand syndrome, a rare, injury-caused condition marked by those symptoms and first described in 1883.

Before her stroke and for 3 days after it, the woman had regularly had vivid dreams, say Matthias Bischof and Claudio L. Bassetti, both neurologists at University Hospital of Bern in Switzerland. For the next 6 weeks, Bischof and Bassetti measured the woman's brain waves as she slept. She displayed normal sleep stages, including rapid-eye movement (REM) sleep, which may not be as crucial to dreaming as scientists once thought (SN: 8/11/01, p. 90: http://www.sciencenews.org/articles/20010811/bob12.asp). The researchers note in an upcoming Annals of Neurology that she reported no dreams, even when awakened during REM sleep, a reliable procedure for dream recall. Brain scans highlighted damage to a small area located deep within and toward the back of the woman's brain.

Good scores on attention and memory tests indicated that the woman didn't simply forget dreams upon awakening. When contacted 1 year after the stroke, she cited occasional, lackluster dreams—no more than one per week.http://louis-j-sheehan.info

Thanks to this rare look at a Charcot-Wilbrand patient, the brain region identified deserves scrutiny as a potentially critical neural component of dreaming, the scientists sayare


Louis J. Sheehan

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Sunday, August 24, 2008

beetles

It turns out that a tree doesn’t have to fall in the forest to make a sound. Upright trees make plenty of sounds, even though human ears can’t hear them. But few aside from botanists would have known about the voices of the trees if two guys had not pounded an old meat thermometer turned ultrasonic microphone into a beetle-infested piñon.

When they did, composer David Dunn and physicist Jim Crutchfield heard “sounds that went on, uninterrupted, for long periods of time. It was a constant ultrasound, and it didn’t matter where you were, the sound was there,” Crutchfield says. “It was bizarre.”

The cacophony came from a tree besieged by drought — and from a frenzy of tree-invading beetles.

The duo’s investigation began after Crutchfield’s New Mexican piñon pine trees came under attack.

“I had to cut down 100 trees on my lot,” he says, “and I wanted to know what killed them.”

It was not the drought that ultimately destroyed the pines but the invasion of a specific type of bark beetle and its accompanying fungus. Crutchfield’s neighbors turned to pesticides to thwart the insect attack, but had no luck. The trees still died.

The same destruction has been happening — en masse — elsewhere as well. The spruce bark beetle has already taken a Connecticut-sized bite out of Alaskan pine forest. And bark beetle outbreaks have desolated thousands of square kilometers of western North American forests, incidentally releasing thousands of tons of carbon into the atmosphere. The additional carbon is a concern because of its link to climate change.

But it was the tree deaths and the failure of the pesticides that first led Crutchfield, who models complex chaotic systems at the University of California, Davis, and Dunn to propose a radical solution to dampen beetle infestations: They want to play deceptive ultrasound to confuse the tree-devouring bugs, luring them away from vulnerable forests and keeping the insects from spreading to new territories.

Crutchfield says the noise could perhaps even stop the beetles from inadvertently adding so much carbon to the air that humans’ contributions to global warming would become irrelevant.

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TWO CHIRPS, AUDIBLE AND ULTRASONICENLARGE | | Top image shows the short and long pulse of a piñon beetle chirp. The bottom shows chirps are loudest (blue) in the audible range but include an ultrasonic component.D. Dunn, J. Crutchfield

The big crunch

The idea to use ultrasound as a beetle-defense tactic began percolating in the pair’s minds about four years ago. As Crutchfield’s trees were dying, Dunn, who is president of the Art and Science Laboratory in Santa Fe, N.M., was fabricating a device to listen to the ultrasonic sounds of nature. The environmental sound recordist had decided to create a high-frequency recorder while working at the Detroit Zoo, where he learned that endangered Tanzanian frogs used ultrasonic calls to find mates.

Dunn and Crutchfield got together to eavesdrop on pine trees and their invading beetles, which led the composer to an idea. He wondered if the beetles could, in any way, detect the ultrasound coming from the trees. As the pines’ liquid-
transporting cells dehydrate, the trees’ water columns cave in, creating ultrasonic pops. Scientists believe that extended periods of dehydration and drought cause the water cells to implode and give off the pops, which are near the 100 to 300 kilohertz range. By comparison, the highest frequency a human can hear is 20 kilohertz.

Crutchfield suggests that the pops may help possible beetle invaders sense whether a tree is ripe for attack and whether they should chomp through to its inner living layers to lay eggs. Healthy trees have a defense against this invasion, he says. By secreting a sticky, toxic ooze, or resin, that flows into the holes beetles bore into the bark, the pines can “pitch out” the insects.

Drought-stressed trees affected by warming temperatures and consequent moisture loss, though, have trouble making the defensive resin to push the beetles out of the bark. And, water-deprived trees, Crutchfield says, generate more ultrasonic pops. So as the beetles successfully chew their way through a tree, they could pick up the sounds of the tree’s cells collapsing.

Amid the popping, Dunn and Crutchfield also picked up on loud, piercing ultrasonic chirps — the beetles’ cries — as well as crunches on the bark. Beetles passing by might hear the crackles, crunches and pops and drop by to get a bite of their own, the physicist says.

“This hypothesis, namely that trees send signals to beetles, needs a lot of experimental work to back it up,” Crutchfield concedes. “It’s difficult to study because, to take one example, no one knows what the insect’s hearing mechanism is or even if it is responding to ultrasound.”

Wood-boring beetles do seem to sense which trees are more vulnerable to attack, but scientists do not yet know how. The mountain pine beetle reacts strongly to chemicals called pheromones that are produced by the insects during their attacks, as well as to kairomones, aromatic compounds produced by the trees, says James Powell, a mathematician from Utah State University in Logan who models the dynamics of beetle invasions in pine forests.

Most entomologists think beetles rely primarily on pheromones, not sound, to communicate, mate and possibly even rally the troops for invasion. Powell has studied the interaction between beetles and pine forests in the Rockies, and he says countering beetle outbreaks with chemicals is hit or miss. Some experiments in Scandinavia have actually shown that using pheromones to lure beetles away from vulnerable trees can exacerbate beetle invasion, Crutchfield says.

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INSECT INFESTATIONENLARGE | Wood-boring beetles are devastating confier forests across western North America. The map shows the locations of recent large-scale infestations by thee species of bark beetles. The graph shows the total area affected by one species.Kenneth Raffa et al., Bioscience June 2008

Crutchfield and Dunn published their “bioacoustic ecology hypothesis” in 2006 as a working paper on the website of the Santa Fe Institute, a center for interdisciplinary research. A revised version will appear in an upcoming Leonardo, a journal highlighting work of artists using science- and technology-based media.

Despite all the existing research on beetle communication, Crutchfield says, entomologists don’t yet know how far each species’s chemical or sound signals can travel.

It’s also not known what actually kills a tree after a beetle infestation. Richard Hofstetter, Crutchfield’s collaborator and an ecologist at Northern Arizona University in Flagstaff, has a beetle farm and looks at the interactions between beetles and the blue stain fungus Ophiostoma minus, which hitchhikes with the beetles into trees. Hofstetter studies whether it’s the beetles’ feeding frenzy, the associated fungal invasion or some combination of the two that kills a tree.http://ljsheehan.livejournal.com

More important for testing the bio-acoustic hypothesis, however, is figuring out the full range of sound signals that the beetles can produce and detect. For that, Crutchfield turned to Jayne Yack, a biologist at Carleton University in Ottawa, Canada.

Listening to bugs

Yack eavesdrops on insects, typically butterflies and moths, to decode their sound signals. Now she has turned her attention to bark beetles. But these insects, she says, are harder to study because they live under tree wood and are small — sometimes as small as the head of a matchstick.http://louis-j-sheehan.info

“We really know very little about how they talk to each other and what signals they send,” Yack says. But “these guys are highly acoustic. They talk to each other all the time, and so they have to have acoustic organs.”

Scientists do know that the male or female in certain wood-boring beetle species has an organ called a pars striden, which looks like a set of ridges on the back or underside of the insect’s head. An insect can “play” these organs by curling up and rubbing its head back and forth against the middle of its body, Yack says.

The beetles seem to make other auditory calls, too. Although Yack is not sure exactly what the sounds mean. She speculates that the calls could signal aggression if one beetle violates another’s territory when the insects are mating. Or the signals, which she says can only travel about 10 centimeters, could alert incoming beetles that they need to spread out while laying eggs in a host tree. If beetle pairs disperse and lay eggs all over the tree, Yack says, there might be less competition for resources and space — at least for the beetles.

Whether the beetles have organs to sense sounds and, if so, whether they use those organs to find drought-stressed trees is still unknown, she says. Yack’s team is now trying to determine if the beetles have sound receptors called tympanals, which can pick up ultrasonic vibration. “We have good candidates for these receptors,” she says, but notes that the team has yet to confirm that the insects have the organs. She expects to submit her research on the question for publication soon.

Next, Yack plans to test if the beetles respond to a recording of the pine trees’ ultrasonic vibrations. “We will put electrodes in certain regions of the beetles’ nervous system, play sounds and see if the nervous system reacts,” she says.

While Yack’s research focuses on understanding insects’ sensory worlds, her work could have important practical implications. If scientists learn what sounds, coupled with what chemicals, beetles use to signal mating cycles and impending invasions, she says, the knowledge could lead to new ways to control the beetles.http://ljsheehan.livejournal.com/

A frenzied loop

Invasive beetles are beginning to move not only northward but also upward, to elevations above their usual habitats, Powell says. Certain species of wood-boring beetles, such as the mountain pine beetle and piñon beetles, are native to lower-altitude forest regions. The bugs help forests thrive by eating old trees and letting new ones grow, he notes. But as warmer temperatures and less rainfall lead to drought, the beetle population is pushed out of check. More trees become vulnerable to beetles, which spread to higher latitudes and altitudes.

Tree species found in these regions not native to the beetle invasions may not be as successful at pitching out beetles and their fungus, Powell says. Beetle attacks on these new, drought-stressed species could devastate forests and start to add large amounts of carbon dioxide into the air, says Werner Kurz, an ecologist at the Canadian Forest Service’s Pacific Forestry Centre in Victoria, Canada. Infested pines ultimately take in less CO² than healthy trees. And dead trees take in none — as the wood breaks down, it releases carbon. So every time a tree is damaged or dies because of a beetle infestation, the bugs indirectly contribute more carbon to the atmosphere.

Based on a model of the beetles’ effect on western Canadian pine forests, Kurz and his colleagues predict that in about 20 years, beetle outbreaks could kill enough trees to release greenhouse gases with a warming effect equivalent to about 990 million metric tons of CO². In a single year, the beetles could add 73 million tons worth of these gases — equivalent to about 10 percent of Canada’s total human-caused emissions for one year, Kurz and his colleagues reported in the April 24 Nature. Those extra gases, if not removed, could lead to further increases in temperatures, which could trigger more beetle population growth, movement to new locales and damage to trees. “We call this a feedback loop,” a positive one, he says, because more beetles lead to more CO².

“The numbers the Canadians have are shocking, and that is just one class of beetle and one class of trees,” Crutchfield says. “If other insects are doing the same thing — I am especially thinking of moths infecting deciduous, boreal forests in Siberia — imagine the damage.” Echoing anthropogenic climate change, the beetles could have their own “entomogenic climate change,” he says.

Buzzing the beetles

Kurz believes that recognition of the insects’ potential impact on the environment could lead to new efforts to control the mountain pine beetle attacks in Canada. Managing beetle outbreaks at their outset, planting new trees and using the dead and eaten ones for wood products or energy, he says, are a few ways humans can keep forests, traditional carbon sinks, from ever becoming carbon sources.http://ljsheehan.livejournal.com/

Crutchfield is more skeptical that such efforts would keep temperatures low enough. According to his models, a continued increase in global temperature is likely, and the beetles’ current reaction to this “early stage of warming” does not bode well for future forest health.

What adds to his concern, he says, is the fact that current countermeasures against the beetles are less than effective.

But, “there is a possibility that you could have an acoustic signal to break up or slow down a beetle infestation,” Crutchfield says. In preliminary field work, he and Dunn played ultrasonic noise to interfere with the beetles’ sense in this acoustic range. The tests, he says, were effective. “Again, the bioacoustic idea is still a hypothesis, one that has to be carefully tested in a lab.” Right now, though, Crutchfield adds, “it is the only alternative I see.”

The method is one that Powell admits might work. “The idea that beetles create sound passes muster with me, so using ultrasound to confuse beetles is possible, at least at short distances,” he says.

And should ultrasonic beetle-blocking turn out to be a dud, Crutchfield says, “We better hope that the beetle-climate feedback loop does not kick in.”Louis J. Sheehan

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Friday, August 15, 2008

zana

Archaeologists working in a valley on the western slopes of Peru's Andes mountains have discovered the earliest known irrigation canals in South America, a find that illuminates the origins of large-scale agriculture in the New World.http://louis-j-sheehan.net

Tom D. Dillehay of Vanderbilt University in Nashville and his colleagues came across three buried canals, stacked one on top of the next, on the southern side of a river running through the Zana Valley. Radiocarbon measurements of carbon fragments date the bottom canal to about 5,380 years ago, the researchers report in an upcoming Proceedings of the National Academy of Sciences. They estimate the ages of the middle and top canals at around 4,390 years and 1,190 years, respectively.

The researchers also found traces of a fourth canal, about 6,700 years old, beneath the others.

Remnants of at least 51 sites once inhabited by people dot the countryside around the canals, Dillehay says. A majority of the sites, ranging from 4,500 to 6,000 years old, include remains of domesticated cotton, beans, squash, and coca. Preserved bits of both wild and cultivated plants have turned up at earlier sites.http://louis-j-sheehan.net

The Zana Valley canals were designed to pipe water from a nearby river into adjoining agricultural fields, Dillehay says. The earliest canal was 2 feet wide and ran for slightly more than 1 mile. Each succeeding canal was built wider, longer, and with a flatter gradient. The top channel was 4 feet wide and stretched about 2.5 miles.

The two older canals were dirt ditches with pebbles and rocks along the bottom. In the third canal, rough stone and burned clay line the channel.

Dillehay's group has also uncovered probable irrigation canals on Peru's north coast at three villages inhabited between 6,500 and 4,700 years ago.

"By 5,000 years ago, irrigation canals likely had developed in lots of different places," Dillehay says.

With a constant supply of water from the canals, farmers could expand their collective food-growing effort to large plots of land.

River sediment eventually filled each ancient canal, according to the researchers. The region's inhabitants periodically built a new canal on top of the previous one to continue using the best path to draw water from the river to the fields.

Several Andean sites from more than 4,000 years ago contain planting areas coated by what appears to be river sediment, which may have overflowed from irrigation ditches, notes archaeologist Michael E. Moseley of the University of Florida in Gainesville. "However, [Dillehay's] article is the first report of ancient irrigation canals that have actually survived," Moseley says.

The Zana Valley lies in an archaeologically neglected region, the arid Andean sierra, which is between about 6,000 and 9,000 feet in elevation. Andean researchers usually focus on coastal areas and high-elevation mountain basins that supported large prehistoric populations, Moseley notes.

Building and maintaining the ancient irrigation canals required a collective effort orchestrated in the name of the gods, he proposes. For religious rituals, inhabitants erected flat-topped mounds just across the river at about the time that they constructed the oldest canal.

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