Wednesday, November 4, 2009

SEISMIC NOISE UNEARTHS LOST HURRICANES

0 comentarios
Seismologists have found a new way to piece together the history of hurricanes in the North Atlantic - by looking back through records of the planet's seismic noise. It's an entirely new way to tap into the rich trove of seismic records, and the strategy might help establish a link between global warming and the frequency or intensity of hurricanes.

"Looking for something like hurricane records in seismology doesn't occur to anybody," said Carl Ebeling, of Northwestern University in Evanston. "It's a strange and wondrous combination."

The research is attempting to address a long-standing debate about whether the warming of sea-surface waters as a result of climate change is producing more frequent or more powerful hurricanes in the North Atlantic. It's a tough question to answer.

Before satellite observations began in the 1960s, weather monitoring was spotty. Ships, planes, and land-based monitoring stations probably missed some hurricanes, which tend to last for about a week or so, Ebeling said. This type of uncertainty poses a problem for scientists, who can’t identify trends until they know what the actual numbers were.

To fill in the historical blanks, Ebeling and colleague Seth Stein are looking to seismic noise, an ever-present background signal that bathes the surface of the Earth. Seismic noise derives its energy from the atmosphere and then gets transmitted through the oceans into the solid earth, where it travels as waves. Seismometers record the noise as very low-amplitude wiggle patterns with much larger, obvious signals that come from earthquakes. Subtle changes in seismic noise frequency and amplitude have long been ignored.

Ebeling and Stein analyzed digital seismograms dating back to the early 90s from two monitoring stations: one in Harvard, Mass., and one in San Juan, Puerto Rico. For this study, the researchers looked at seismograms recorded during known hurricanes in an attempt to see whether patterns produced during hurricanes look predictably different from patterns produced during regular storms or when there are no storms at all.

Their preliminary results suggest that hurricanes do indeed produce recognizable patterns, and the waves generated by hurricanes travel large distances. The Harvard station recorded signals from Hurricane Andrew more than a thousand kilometers away.

"There's definitely something there that shows this can be workable," Ebeling said. "This is something new and interesting."

At least one major hurdle remains before scientists will be able to pull together a complete hurricane history out of the seismic records. For most of the 20th century, seismograms recorded data on rolls of paper. Those records, which contain hundreds of thousands of hours of data, will need to be digitized. Ebeling is looking for an efficient way to do that.

The Geological Society of America

KILLER ALGAE A KEY PLAYER IN MASS EXTINCTIONS

0 comentarios
Supervolcanoes and cosmic impacts get all the terrible glory for causing mass extinctions, but a new theory suggests lowly algae may be the killer behind the world's great species annihilations.

Today, just about anywhere there is water, there can be toxic algae. The microscopic plants usually exist in small concentrations, but a sudden warming in the water or an injection of dust or sediment from land can trigger a bloom that kills thousands of fish, poisons shellfish, or even humans.

James Castle and John Rodgers of Clemson University think the same thing happened during the five largest mass extinctions in Earth's history. Each time a large die off occurred, they found a spike in the number of fossil algae mats called stromatolites strewn around the planet. Castle will be presenting the research on Monday, 19 October, at the annual meeting of the Geological Society of American in Portland, Oregon, USA.

"If you go through theories of mass extinctions, there are always some unanswered questions," Castle says. "For example, an impact — how does that cause species to go extinct? Is it climate change, dust in the atmosphere? It's probably not going to kill off all these species on its own."

But as the nutrient-rich fallout from the disaster lands in the water, it becomes food for algae. They explode in population, releasing chemicals that can act as anything from skin irritants to potent neurotoxins. Plants on land can pick up the compounds in their roots, and pass them on to herbivorous animals.

If the theory is right, it answers a lot of questions about how species died off in the ancient world. It also raises concerns for how today's algae may damage the ecosystem in a warmer world.

"Algae growth is favored by warmer temperatures," Castle says. "You get accelerated metabolism and reproduction of these organisms, and the effect appears to be enhanced for species of toxin-producing cyanobacteria."

Castle added that toxic algae in the United States appear to be migrating slowly northward through the country's ponds and lakes, and along the coast as temperatures creep upward. Their expanding range portends a host of problems for fish and wildlife, but also for humans, as algae increasingly invade reservoirs and other sources of drinking water.

The Geological Society of America

IMPROVED ELECTRIC PROPULSION COULD BOOST SATELLITE LIFETIMES

0 comentarios
Researchers at the Georgia Institute of Technology have won a $6.5 million grant to develop improved components that will boost the efficiency of electric propulsion systems used to control the positions of satellites and planetary probes.

Focusing on improved cathodes for devices known as Hall effect thrusters, the research would reduce propellant consumption in commercial, government and military satellites, allowing them to remain in orbit longer, be launched on smaller or cheaper rockets, or carry larger payloads. Sponsored by the U.S. Defense Advanced Research Projects Agency Defense Sciences Office (DARPA-DSO), the 18-month project seeks to demonstrate the use of propellant-less cathodes with Hall effect thrusters.

“About 10 percent of the propellant carried into space on satellites that use an electric propulsion system is essentially wasted in the hollow cathode that is part of the system,” said Mitchell Walker, an assistant professor in Georgia Tech’s School of Aerospace Engineering and the project’s principal investigator. “Using field emission rather than a hollow cathode, we are able to pull electrons from cathode arrays made from carbon nanotubes without wasting propellant. That will extend the life of the vehicle by more efficiently using the limited on-board propellant for its intended purpose of propulsion.”

To maintain their positions in space or to reorient themselves, satellites must use small thrusters that are either chemically or electrically powered. Electrically-powered thrusters use electrons to ionize an inert gas such as xenon. The resulting ions are then ejected from the device to generate thrust.

In existing Hall effect thrusters, a single high-temperature cathode generates the electrons. A portion of the propellant -- typically about 10 percent of the limited supply carried by the satellite -- is used as a working fluid in the traditional hollow cathode. The DARPA-funded research would replace the hollow cathode with an array of field-effect cathodes fabricated from bundles of multi-walled carbon nanotubes. Powered by on-board batteries and photovoltaic systems on the satellite, the arrays would operate at low power to produce electrons without consuming propellant.

Walker and collaborators at the Georgia Tech Research Institute (GTRI) have already demonstrated field-effect cathodes based on carbon nanotubes. This work was presented at the 2009 AIAA Joint Propulsion Conference held in Denver, Colo. The additional funding will support improvements in the devices, known as carbon nanotube cold cathodes, and lead to space testing as early as 2015.

“This work depends on our ability to grow aligned carbon nanotubes precisely where we want them to be and to exacting dimensions,” said Jud Ready, a GTRI senior research engineer and Walker’s collaborator on the project. “This project leverages our ability to grow well-aligned arrays of nanotubes and to coat them to enhance their field emission performance.”

In addition to reducing propellant consumption, use of carbon nanotube cathode arrays could improve reliability by replacing the single cathode now used in the thrusters.

“Existing cathodes are sensitive to contamination, damaged by the ionized exhaust of the thruster, and have limited life due to their high-temperature operation,” Ready noted. “The carbon nanotube cathode arrays would provide a distributed cathode around the Hall effect thruster so that if one of them is damaged, we will have redundancy.”

Before the carbon nanotube cathodes developed by Georgia Tech can be used on satellites, however, their lifetime will have to be increased to match that of a satellite thruster, which is typically 2,000 hours or more. The devices will also have to withstand the mechanical stresses of space launches, turn on and off rapidly, operate consistently and survive the aggressive space environment.

Part of the effort will focus on special coating materials used to protect the carbon nanotubes from the space environment. For that part of the project, Walker and Ready are collaborating with Lisa Pfefferle in the Department of Chemical Engineering at Yale University.

The researchers are testing their cathodes with the same Busek Hall effect thruster that flew on the U.S. Air Force’s TacSat-2 satellite. In addition, the cathodes will be operated with Hall effect thrusters developed by Pratt & Whitney and donated to Georgia Tech. The researchers are also collaborating with L-3 ETI on the electrical power system and with American Pacific In-Space Propulsion on flight qualification of the hardware.

The ability to control individual cathodes on the array could provide a new capability to vector the thrust, potentially replacing the mechanical gimbals now used.

The use of carbon nanotubes to generate electrons through the field-effect process was reported in 1995 by a research team headed by Walt de Heer, a professor in Georgia Tech’s School of Physics. Field emission is the extraction of electrons from a conductive material through quantum tunneling that occurs when an external electric field is applied.

The improved carbon nanotube cathodes should advance the goals of reducing the cost of launching and maintaining satellites.

“Thrust with less propellant has been one of the major goals driving research into satellite propulsion,” said Walker, who is director of Georgia Tech’s High-Power Electric Propulsion Laboratory. “Electric propulsion is becoming more popular and will benefit from our innovation. Ultimately, we will help improve the performance of in-space propulsion devices.”

Georgia Institute of Technology

VIRTUAL SOLUTION TO DRIVING PHOBIAS

0 comentarios

Nervous drivers are being helped to overcome their road phobias by donning Cyclops-style goggles that transport them to a three-dimensional virtual world.

Researchers at The University of Manchester have recruited volunteers with a variety of driving phobias to test whether virtual reality can be used alongside conventional psychological therapies to help tackle their fears.

The Virtual Reality Exposure Treatment (VRET) will allow participants to drive on virtual roads and confront their fears, whether they might be driving over bridges, overtaking slow-moving traffic or taking to the motorway or dual-carriageway.

“Phobias may develop from a real-life event but the levels of anxiety and avoidance that results becomes wholly disproportionate to the incident that led to the phobia and can become a major disruption to the way people lead their lives,” said Caroline Williams, who will be carrying out the research in Manchester’s School of Psychological Sciences.

“A fear of driving, whether it has developed following a road traffic accident or for other reasons, can escalate into a situation where individuals are too scared to drive at all.

“The advantage of using VRET is that it can be carried out in a safe environment rather than on real roads, which in extreme cases, could put the volunteers, therapists and possibly other road-users at risk through the adoption of defensive driving behaviours, such as braking harder or going slow on motorways, by the phobic subject. It also helps the person with a phobia to tolerate the level of exposure to the fear as it is tightly controlled.”

The volunteers will wear the hi-tech goggles, which resemble those worn by the X-Men character Cyclops, to transport them into a virtual driving world, while sensors placed on their fingertips and chest area will measure anxiety levels.

Some of the volunteers taking part in the study have developed their phobia following an accident but others have no obvious cause. Among the phobias are fears of driving over bridges and fears of motorways: even the sight of blue motorway signs can be a trigger for some people.

Ms Williams added: “Many of our volunteers have found it difficult to get treatment for their phobia through the NHS and, as a result, have been untreated for many years. The virtual scenario will allow volunteers to come to terms with and challenge their own fear in a safe and controlled environment. We hope this will result in less resistance to treatment, increased awareness of the need for such treatments and may even reduce the amount of time people spend in therapy due to its efficiency.

“Future studies could use the virtual treatment to tackle other phobias which could mean a major breakthrough in this type of therapy; the possibilities could be endless.”

The research, which is being led by Professor Nick Tarrier, has been funded by the European Union.

(Photo: U. Manchester)

The University of Manchester

FRACTURE ZONES ENDANGER TOMBS IN VALLEY OF KINGS

0 comentarios

Ancient choices made by Egyptians digging burial tombs may have led to today's problems with damage and curation of these precious archaeological treasures, but photography and detailed geological mapping should help curators protect the sites, according to a Penn State researcher.

"Previously, I noticed that some tomb entrances in the Valley of Kings, Luxor, Egypt, were aligned on fracture traces and their zones of fracture concentration," said Katarin A. Parizek, instructor in digital photography, Department of Integrative Arts. "From my observations, it seems that tomb builders may have intentionally exploited these avenues of less resistant limestone when creating tombs."

Fracture traces are the above-ground indication of underlying zones of rock fracture concentrations. They can be between 5 and 40 feet wide, but average about 20 feet and can be as long as a mile. Lineaments are similar geological features that exceed one mile in length. Geologists suggest that fracture traces are good locations for drilling water wells and probably the highly fractured rock made it easier for the Egyptians to dig tombs.

Working with Richard R. Parizek, professor of geology and geoenvironmental engineering, Parizek has now looked at 33 of the 63 known tombs in the Valley of Kings. She reported her results Oct. 18 at the annual meeting of the Geological Society of America in Portland, Ore.

"We have now documented nine tombs in detail, photographing and mapping the entire tombs inside and out, and preliminary observations have been made in another nine, which still have to be mapped in detail," said Parizek. "We have recorded 14 more tombs through field observations, but still need to map and photograph these as well."

Of the 63 tombs in the Valley of the Kings, so far 30 have been identified by Parizek as lying on fracture traces, two lie diagonal to a trace and one is completely off of this type of geological structure.

The importance of these geological features is not just that they allow easier tomb creation, but the fracture traces are natural entry points for water, which sometimes damage tombs.

"We have seen evidence of seven separate flood events in four tombs so far," said Parizek.

When it does rain in the area, water enters the fracture traces and runs through the zones of fracture. Because so many of the tombs are located on the traces, the water runs into the tombs destroying wall and ceiling paintings and causing the tomb surfaces to spall or flake off. Even if archaeological curators divert water away from the entrances of known tombs, they may be directing the water to currently undiscovered tombs and flooding them.

"Archaeologists try very hard to mitigate flooding in the tombs, but it becomes even harder if there are tombs flooding that no one knows about," said Parizek.

The geological information the team has been gathering is now allowing archaeologists to plan better ways to stop the flooding of both known and unknown tombs by diverting the water away from traces and exposed entrances.

Parizek also notes that archaeologists are using this geological information along with archaeological clues to explore for new tombs and other archaeological sites in the Valley of Kings. In February 2006, KV63 was discovered by professor Otto Schaden.

"This tomb is localized along master joints immediately adjacent to a zone of fracture concentration that we mapped in 2002," said Parizek.

This discovery supplied evidence the Parizeks' original hypothesis that tombs were dug on fracture traces and into fracture zones is correct.

For the last two years, Zahi Hawass, secretary general of the Supreme Council of Antiquities and a renowned Egyptian archaeologist, has been leading an extensive exploration effort within the Valley of Kings.

"He is using our geological information along with archaeological clues to guide excavations," said Parizek.

The researchers hope to investigate and map the geology of more tombs in the future and to combine the photographs and maps to create 3-D images of the tombs.

(Photo: Katarin Parizek, Penn State)

UCSB ANTHROPOLOGIST STUDIES HUMAN LIFE SPAN, EVOLUTION OF PHYSIOLOGY

0 comentarios

A remote Amazonian tribe in central Bolivia may offer proof that heart attack and stroke –– the leading causes of death in the United States and other developed countries –– were rare occurrences throughout most of human history. The tribe, known as the Tsimane, may also prove that chronic inflammation, a condition currently associated with cardiovascular disease, may not play as great a role as medical research has suggested.

"What we discovered is that inflammation doesn't always hold as one of the leading causes of heart disease," said Michael Gurven, professor of anthropology at UC Santa Barbara. "Chronic inflammation in the absence of other factors doesn't seem to increase heart disease."

Gurven's findings were published recently in the science journal PLoS ONE, but his research on the correlation between chronic inflammation and heart disease is only a small piece of a larger puzzle. He is studying the evolution of physiological systems –– immune, cardiovascular, renal, digestive –– that have contributed to humans' ever-increasing life span, but have also made them susceptible to a host of chronic diseases. Gurven believes that his continuing work with the Tsimane may call into question a variety of other commonly held medical beliefs.

"All humans are not the same. Local adaptations have been shaped for dealing with local environments," he said. "The more we learn about that, the more we learn that the hard and fast rules about risk factors in the biomedical tradition aren't so hard and fast. There are general ideas about what to do to stay healthy, but a lot of the details about why some lifestyle changes work for some but not others are unknown."

As an example, Gurven noted that many Tsimane suffer from parasites, a condition that may also offer the benefit of lower levels of total blood cholesterol –– particularly the LDL "bad" cholesterol –– and that parasites may shift the immune system in other ways that foster better heart health. He added that because parasites keep the immune system operating at a low but constant level of activity, allergies and asthma –– which result from the immune system suddenly going into overdrive –– are virtually non-existent among the Tsimane.

Gurven chose to study the Tsimane, who inhabit a vast area of lowland forests and savannas east of the Andes, because they still live a relatively traditional lifestyle –– fishing, hunting and gathering, and living in extended family clusters. Other groups with similar lifestyles exist, noted Gurven, but their very low population numbers make it extremely difficult to study older adults. "The Tsimane population is large enough that we can study almost all of the adults over age 40," he said.

Gurven conducts his research under the auspices of the Tsimane Health and Life History Project, which he co-founded in 2001 with Hillard Kaplan, a professor of anthropology at the University of New Mexico. The goal of the project is to understand the impacts of ecology and evolution on the shaping of the human life course. The focus is on health, growth, development, aging, economics, and biodemography of small-scale populations of hunter-gatherers and horticulturists. The project combines biomedical and anthropological research with medical attention among the Tsimane.

"I'm trying to understand the ecology of the past that has shaped the way our bodies function in traditional environments, and then use that knowledge to understand how our bodies function in modern environments. No single group can represent the past, and no group is pristine, but the Tsimane are closer than most," Gurven said.

The next step in his research is to increase his sample size. He is expanding his work to include over 35 additional villages, which will encompass over 95 percent of all Tsimane. Working with a medical doctor, he also plans to bring high-tech equipment to the field to conduct echocardiograms and ultrasound exams on the people to whom they provide medical care. "The true gold standard is looking at arteries," Gurven said. "We'll do echocardiogram on the carotid artery to look at a cross section and see how clogged it is –– or isn't. We anticipate very little clogging, if any, but if we do find it, it could be the case that it's not manifesting itself in typical heart disease."

Gurven and his team will also take a more in-depth look at other organs, including the heart, kidneys, and liver, to study the correlations between infectious exposure, organ damage and chronic diseases, such as diabetes, heart disease, or renal failure. "We're trying to see whether or not the pathology we see is a direct effect of pathogens or whether there's evidence of a similar disease process that we see here in the West," he said. "In the kidneys, we might see damage from infection, like from streptococcus bacteria. When we look at the heart, we might see damage from rheumatic fever or Chagas disease," Gurven continued. "In the West, when we see kidney disease or heart disease it's generally due to obesity, stress, diet, and other lifestyle factors."

(Photo: Rod Rolle)


Followers

Archive

 

Selected Science News. Copyright 2008 All Rights Reserved Revolution Two Church theme by Brian Gardner Converted into Blogger Template by Bloganol dot com