lunes, 14 de marzo de 2011
Henry VIII may have had two rare medical conditions that could explain both his health issues later in life and the miscarriages of two of his wives.
An X-linked genetic disease might have caused Henry to become paranoid and anxious after his 40th birthday.
An unusual blood type might have caused the bodies of his wives to attack their fetuses.
Among a long list of personality quirks and historical drama, Henry VIII is known for the development of health problems in mid-life and a series of miscarriages for two of his wives. In a new study, researchers propose that Henry had an X-linked genetic disorder and a rare blood type that could explain many of his problems.
By suggesting biological causes for significant historical events, the study offers new ways to think about the infamous life of the notorious 16th-century British monarch, said Catarina Whitley, a bioarchaeologist who completed the research while at Southern Methodist University.
"What really made us look at Henry was that he had more than one wife that had obstetrical problems and a bad obstetrical history," said Whitley, now with the Museum of New Mexico. "We got to thinking: Could it be him?"
Plenty of historians have written about Henry's health problems. As a young man, he was fit and healthy. But by the time of his death, the King weighed close to 400 pounds. He had leg ulcers, muscle weakness, and, according to some accounts, a significant personality shift in middle age towards more paranoia, anxiety, depression and mental deterioration.
Among other theories, experts have proposed that Henry suffered from Type II diabetes, syphilis, an endocrine problem called Cushing's syndrome, or myxedema, which is a byproduct of hypothyroidism.
All of those theories have flaws, Whitley said, and none address the monarch's reproductive woes. Two of his six wives -- Ann Boleyn and Katherine of Aragon -- are thought to have suffered multiple miscarriages, often in the third trimester.
To explain those patterns, Whitley and colleague Kyra Kramer offer a new theory: Henry may have belonged to a rare blood group, called Kell positive. Only 9 percent of the Caucasian population belongs to this group.
When a Kell positive man impregnates a Kell negative woman, there is a 50 percent chance of provoking an immune response in the woman's body that attacks her developing fetus. The first baby of a Kell positive father and Kell negative mother is usually fine. But some of the baby's blood will inevitably get into the mother's body -- either during development or at birth, leading her to produce antibodies against the baby's Kell antigens.
As a result, in subsequent pregnancies, babies may suffer from extra fluid in their tissues, anemia, jaundice, enlarged spleens, or heart failure, often leading to miscarriage between about 24 and 28 weeks of pregnancy.
Ann Boleyn is a classic example of this pattern, Whitley said. According to some accounts (and there is still much dispute about the details, including how many pregnancies there actually were), Elizabeth -- Anne's first daughter with Henry -- was born healthy and without complications. But her second and third pregnancies miscarried at about month six or seven.
Katherine of Aragon carried as many as six pregnancies. Only her fifth led to the birth of a live and health baby, a daughter named Mary.
In addition to Henry's problematic blood type, the researchers propose that he also had a rare genetic disorder called McLeod syndrome. Carried on the X-chromosome, the disease generally affects only men and usually sets in around age 40 with symptoms including heart disease, movement disorders and major psychological symptoms, including paranoia and mental decline.
The disease could explain many of Henry's physical ailments, the researchers propose. It could also explain why he may have become more despotic as he grew older and why he shifted from supporting Anne to having her beheaded.
"This gives us an alternative way of interpreting Henry and understanding his life," Whitley said. "It gives us a new way to look at the reasons he changed."
Without any genetic evidence, however, there's no way to know for sure whether the new theories are right, said Retha Warnicke, a historian at Arizona State University and author of The Rise and Fall of Anne Boleyn: Family Politics at the Court of Henry VIII.
Other conditions could explain the miscarriages, she said. Until the late 19th-century, midwives did not wash their hands. And in Henry's time, up to half of all children died before age 15.
As for Henry's woes, dementia could explain his personality shifts, she added. Lack of exercise -- after an active youth -- combined with a hearty appetite could have led to his obesity and related ills.
"Could is the big word," Warnicke said. "It's an interesting theory and it's possibly true, but it can't be proven without some clinical evidence, and there is none."
The massive earthquake that hit Japan sped up Earth's spin by a microsecond and tilted the axis by several inches.
The shift happened when massive amounts of the planet's crust tumbled inside a 250-mile long crack that opened up six miles beneath the Pacific Ocean.
Changes in Earth's tilt are associated with ice ages.
This weekend, it wasn't just the shift to Daylight Saving's Time that reset our clocks. Mother Nature tweaked time by speeding up Earth's spin a bit in response to the killer earthquake that rocked Japan on Friday.
"There was a redistribution of an enormous amount of the Earth's crust," theoretical physicist Michio Kaku, with the City College of New York, told Discovery News. "It actually shortened the time of the day, and also shifted the axis of the Earth."
The 8.9-magnitude quake -- the fifth largest in recorded history -- shaved about one-millionth of second off our day and tilted the planet's axis by several inches.
Looking to help the victims of the disaster in Japan? Make your contribution to GlobalGiving's relief fund here.
Kaku says the phenomenon is similar to what happens when a dancer folds in his or her arms and speeds up in a spin.
The shifting of tectonic plates beneath the Pacific Ocean opened up a crack about 250 miles long, causing a good portion of Earth's crust to tumble inside.
"We know how much the Earth contracted as consequence of that, then you do the math," Kaku said.
While the speeding up of Earth isn't expected to have any immediate or long term impacts, the tilt of the axis might.
"There is still a scientific debate as to what causes ice ages," Kaku said. "The leading theory is that there are tiny perturbations in the axis of the Earth as it turns around the sun that accumulate with time. These small shifts, this wobbling of the axis of the Earth may in fact cause ice ages."
"Every century, we have several of these monster earthquakes so it's hard to estimate exactly how much of an impact this earthquake would have on an ice age, for example," Kaku added.
The earthquake was the most powerful to hit Japan since official record-keeping began in late 1800s, says the U.S. Geological Survey.
It struck about 80 miles off Japan's east coast, roughly 240 miles northeast of Tokyo, at a depth of six miles. The death toll from the earthquake, a massive tsunami that followed, and an ongoing serious of aftershocks is expected to reach in the thousands.
The prehistoric relatives of this megafish inhabited many parts of the world, but today gars live only in North and Central America.
Of the seven known gar species, the alligator is the largest, reaching up to ten feet (three meters) long and tipping the scales at up to 300 pounds (140 kilograms). These menacing-looking behemoths are generally olive green or yellow and have a heavily scaled body. A tooth-filled mouth and wide, alligator-like snout give the species its name.
These freshwater giants may look fierce, but attacks against people are unknown. They can pose a passive danger, though—the fish's eggs are poisonous to humans if ingested.
Adult gars have few natural predators, although alligators have been known to attack them. Young are preyed upon by larger fish. Alligator gars prey on fish, but they are opportunistic and have been known to feed on everything from waterfowl and small turtles to carrion.
Alligator gars are found throughout much of the coastal U.S. Southeast. They inhabit waters as far west as Texas and Oklahoma, as far north as the Mississippi River Basin and the lower Ohio and Missouri river systems, and southern drainages well into Mexico.
Gars inhabit lakes, bayous, and bays and are able to tolerate brackish and even salt water. But these toothy giants prefer large, slow-moving rivers, particularly those with wide floodplains, where shallow waters provide hatchlings with some protection from predators.
Unfortunately for the alligator gar, flood-control measures such as dams and dikes have dramatically altered their riverine ecosystems and largely eliminated their preferred spawning habitats across North America. These breeding challenges have contributed to significant population declines across much of the animal's range.
Alligator gars are also targeted by both commercial and sport fisheries and have frequently been overfished. They are now protected by law in parts of their range.
With eyebrows, hair, and skin still intact after more than 600 years, a remarkably preserved Chinese "wet mummy" remains bundled in her quilt after centuries in a flooded coffin.
Removed from her wooden casket on March 1, the body had been found in a tomb accidentally uncovered by roadbuilders near the city of Taizhou (map).
"Wet mummies survive so well because of the anaerobic conditions of their burials," said archaeologist Victor Mair. That is, water unusually void of oxygen inhibits bacteria that would normally break down a body.
Unlike ancient Egyptian mummies, the corpse—likely from the Ming dynasty (1368 to 1644)—was probably preserved only accidentally, said Mair, of the University of Pennsylvania.
"I don't know of any evidence that Chinese ever intentionally mummified their deceased," he said. "Whoever happened to encounter the right environment might become a preserved corpse."
Photograph by Gu Xiangzhong, Xinhua/Corbis
Staff members from China's Taizhou Museum carefully raise the mummy—one of three found during a road expansion—from her wooden coffin on March 1.
The fully dressed, 5-foot-long (1.5-meter-long) body was buried with luxury items, including a jade ring, a silver hairpin, and more than 20 pieces of Ming-dynasty clothing.
The lack of identifying insignia such as a phoenix or dragon, though, suggests the wet mummy wasn't royal, said Timothy Brook, a historian at the University of British Columbia's Institute of Asian Research.
"Her headgear is sort of ordinary," Brook said. "There's nothing that sets her apart from anyone else. ... She was probably just a well-off person."
You Can't Take It With You?
Photograph by Gu Xiangzhong, Xinhua/Corbis
A worker from the Taizhou Museum cleans the Chinese wet mummy's large jade ring on March 3.
Jade was associated with longevity in ancient China. But in this case, the jade ring was "probably a sign of her wealth instead of a sign of any concern about the afterlife," Brook said.
Good Hair Day
Photograph by Gu Xiangzhong, Xinhua/Corbis
A museum worker removes the female mummy's cap on March 3, revealing hair held in place by a still bright silver hairpin—a fairly standard example of the type worn by Ming-dynasty women, Brook said.
Neither Brook nor the University of Pennsylvania's Mair know why the wet mummy's head appears dyed purple beneath her cap, though Mair speculates it may have to do with natural minerals in the water.
The woman's age at death is unknown, but her unlined face suggests she was fairly young.
"She's certainly an adult," Brook said. "She's not an old woman."
Photograph from Barcroft/Fame Pictures
The newfound mummy rests on a plastic sheet after being removed from her flooded coffin on March 1.
In ancient China, it was believed that the newly dead would appear before supernatural judges.
"If you were found to be morally worthy," Brook explained, "you would be sent off for reincarnation—as a deity if you were fantastic, as a human being if you were good, as an animal if you were less good, and as a bug or a worm if you'd been really bad."
Submerged in the brownish liquid that likely preserved it, the Ming dynasty-era mummy lies in her wooden coffin prior to her removal on March 1.
The University of Pennsylvania's Mair thinks the liquid is oxygen-poor water that leaked into the coffin and not any type of special preservation fluid.
Photograph by Gu Xiangzhong, Xinhua/Corbis
A so-called exorcism coin adorns the chest of the newfound Chinese "wet mummy."
"My guess would be that the coin was placed on the body as a kind of charm against malevolent influences," Brook said.
Still unknown is whether the woman was buried with any written documents or inscribed pottery—a common practice in Ming-dynasty China.
"If you were a person of any importance, you had someone write a [remembrance] or a brief biography," Brook said, "and that biography would often be posted at the burial site and a copy buried with you as well, to identify who you are" in the afterlife.
Radioactive particles from the failing Fukushima Daiichi nuclear power station pose little immediate risk to North America, and should fall into the Pacific before reaching western shores.
Using a publicly available modeling system for airborne pollutants developed by the National Oceanic and Atmospheric Administration, Weather Underground’s Jeff Masters has modeled the spread of radioactive plumes. So far, the “great majority of these runs” have seen the plumes float over the Pacific, reaching eastern Siberia and the western coast of North America in about a week.
“Such a long time spent over water will mean that the vast majority of the radioactive particles will settle out of the atmosphere or get caught up in precipitation and rained out,” wrote Masters. “It is highly unlikely that any radiation capable of causing harm to people will be left in the atmosphere after seven days and 2000-plus miles of travel distance.”
A press release issued March 13 by the U.S. Nuclear Regulatory Commission echoed Masters’ speculation. “Given the thousands of miles between the two countries, Hawaii, Alaska, the U.S. Territories and the U.S. West Coast are not expected to experience any harmful levels of radioactivity,” (pdf) they announced.
Just as some drivers obey the speed limit while others treat every road as if it were the Autobahn, some stars move through space faster than others. NASA's Wide-field Infrared Survey Explorer, or WISE, captured this image of the star Alpha Camelopardalis, or Alpha Cam, in astronomer-speak, speeding through the sky like a motorcyclist zipping through rush-hour traffic. The supergiant star Alpha Cam is the bright star in the middle of this image, surrounded on one side by an arc-shaped cloud of dust and gas -- a bow shock -- which is colored red in this infrared view.
Such fast-moving stars are called runaway stars. The distance and speed of Alpha Cam is somewhat uncertain. It is probably somewhere between 1,600 and 6,900 light-years away and moving at an astonishing rate of somewhere between 680 and 4,200 kilometers per second (between 1.5 and 9.4 million mph). It turns out that WISE is particularly adept at imaging bow shocks from runaway stars. Previous examples can be seen around Zeta Ophiuchi , AE Aurigae, and Menkhib. But Alpha Cam revs things up into a different gear. To put its speed into perspective, if Alpha Cam were a car driving across the United States at 4,200 kilometers per second, it would take less than one second to travel from San Francisco to New York City!
Astronomers believe runaway stars are set into motion either through the supernova explosion of a companion star or through gravitational interactions with other stars in a cluster. Because Alpha Cam is a supergiant star, it gives off a very strong wind. The speed of the wind is boosted in the forward direction the star is moving in space. When this fast-moving wind slams into the slower-moving interstellar material, a bow shock is created, similar to the wake in front of the bow of a ship in water. The stellar wind compresses the interstellar gas and dust, causing it to heat up and glow in infrared. Alpha Cam's bow shock cannot be seen in visible light, but WISE's infrared detectors show us the graceful arc of heated gas and dust around the star.http://www.blogger.com/img/blank.gifhttp://www.blogger.com/img/blank.gif
JPL manages and operates the Wide-field Infrared Survey Explorer fohttp://www.blogger.com/img/blank.gifr NASA's Science Mission Directorate, Washington. The principal investigator, Edward Wright, is at UCLA. The mission was competitively selected under NASA's Explorers Program managed by the Goddard Space Flight Center, Greenbelt, Md. The science instrument was built by the Space Dynamics Laboratory, Logan, Utah, and the spacecraft was built by Ball Aerospace & Technologies Corp., Boulder, Colo. Science operations and data processing take place at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA.
More information is online at http://www.nasa.gov/wise and http://wise.astro.ucla.edu and http://jpl.nasa.gov/wise .
"We have measured the distance to the most distant mature cluster of galaxies ever found," says the lead author of the study in which the observations from ESO's VLT have been used, Raphael Gobat (CEA, Paris). "The surprising thing is that when we look closely at this galaxy cluster it doesn't look young -- many of the galaxies have settled down and don't resemble the usual star-forming galaxies seen in the early Universe."
Clusters of galaxies are the largest structures in the Universe that are held together by gravity. Astronomers expect these clusters to grow through time and hence that massive clusters would be rare in the early Universe. Although even more distant clusters have been seen, they appear to be young clusters in the process of formation and are not settled mature systems.
The international team of astronomers used the powerful VIMOS and FORS2 instruments on ESO's Very Large Telescope (VLT) to measure the distances to some of the blobs in a curious patch of very faint red objects first observed with the Spitzer space telescope. This grouping, named CL J1449+0856 , had all the hallmarks of being a very remote cluster of galaxies . The results showed that we are indeed seeing a galaxy cluster as it was when the Universe was about three billion years old -- less than one quarter of its current age .
Once the team knew the distance to this very rare object they looked carefully at the component galaxies using both the NASA/ESA Hubble Space Telescope and ground-based telescopes, including the VLT. They found evidence suggesting that most of the galaxies in the cluster were not forming stars, but were composed of stars that were already about one billion years old. This makes the cluster a mature object, similar in mass to the Virgo Cluster, the nearest rich galaxy cluster to the Milky Way.
Further evidence that this is a mature cluster comes from observations of X-rays coming from CL J1449+0856 made with ESA's XMM-Newton space observatory. The cluster is giving off X-rays that must be coming from a very hot cloud of tenuous gas filling the space between the galaxies and concentrated towards the centre of the cluster. This is another sign of a mature galaxy cluster, held firmly together by its own gravity, as very young clusters have not had time to trap hot gas in this way.
As Gobat concludes: "These new results support the idea that mature clusters existed when the Universe was less than one quarter of its current age. Such clusters are expected to be very rare according to current theory, and we have been very lucky to spot one. But if further observations find many more then this may mean that our understanding of the early Universe needs to be revised."
 The strange name refers to the object's position in the sky.
 The galaxies appear red in the picture partly because they are thought to be mainly composed of cool, red stars. In addition the expansion of the Universe since the light left these remote systems has increased the wavelength of the light further so that it is mostly seen as infrared radiation when it gets to Earth.
 The astronomers measured the distance to the cluster by splitting the light up into its component colours in a spectrograph. They then compared this spectrum with one of a similar object in the nearby Universe. This allowed them to measure the redshift of the remote galaxies -- how much the Universe has expanded since the light left the galaxies. The redshift was found to be 2.07, which means that the cluster is seen about three billion years after the Big Bang.
The latest evidence of the dominant role humans play in changing Earth's climate comes not from observations of Earth's ocean, atmosphere or land surface, but from deep within its molten core.
Scientists have long known that the length of an Earth day -- the time it takes for Earth to make one full rotation -- fluctuates around a 24-hour average. Over the course of a year, the length of a day varies by about 1 millisecond, getting longer in the winter and shorter in the summer. These seasonal changes in Earth's length of day are driven by exchanges of energy between the solid Earth and fluid motions of Earth's atmosphere (blowing winds and changes in atmospheric pressure) and its ocean. Scientists can measure these small changes in Earth's rotation using astronomical observations and very precise geodetic techniques.
But the length of an Earth day also fluctuates over much longer timescales, such as interannual (two to 10 years), decadal (approximately 10 years), or those lasting multiple decades or even longer. A dominant longer timescale mode that ranges from 65 to 80 years was observed to change the length of day by approximately 4 milliseconds at the beginning of the 20th century.
These longer fluctuations are too large to be explained by the motions of Earth's atmosphere and ocean. Instead, they're due to the flow of liquid iron within Earth's outer core, where Earth's magnetic field originates. This fluid interacts with Earth's mantle to affect Earth's rotation. While scientists cannot observe these flows directly, they can deduce their movements by observing Earth's magnetic field at the surface. Previous studies have shown that this flow of liquid iron in Earth's outer core oscillates, in waves of motion that last for decades with timescales that correspond closely to long-duration variations in Earth's length of day.
Still other studies have observed a link between the long-duration variations in Earth's length of day and fluctuations of up to 0.2 degrees Celsius (0.4 degree Fahrenheit) in Earth's long-term global average surface air temperature.
So how might all three of these variables -- Earth's rotation, movements in Earth's core (formally known as the core angular momentum) and global surface air temperature -- be related? That's what researchers Jean Dickey and Steven Marcus of NASA's Jet Propulsion Laboratory, Pasadena, Calif., and colleague Olivier de Viron of the Universite Paris Diderot and Institut de Physique du Globe de Paris in France, set out to discover in a first-of-its-kind study.
The scientists mapped existing data from a model of fluid movements within Earth's core and data on yearly averaged length-of-day observations against two time series of observed annual global average surface temperature: one from NASA's Goddard Institute of Space Studies in New York that extends back to 1880, and another from the United Kingdom's Met Office that extends back to 1860. Since total air temperature is composed of two components -- temperature changes that occur naturally and those caused by human activities -- the researchers used results from computer climate models of Earth's atmosphere and ocean to account for temperature changes due to human activities. These human-produced temperature changes were then subtracted from the total observed temperature records to generate corrected temperature records.
The researchers found that the uncorrected temperature data correlated strongly with data on movements of Earth's core and Earth's length of day until about 1930. They then began to diverge substantially: that is, global surface air temperatures continued to increase, but without corresponding changes in Earth's length of day or movements of Earth's core. This divergence corresponds with a well-documented, robust global warming trend that has been widely attributed to increased levels of human-produced greenhouse gases.
But an examination of the corrected temperature record yielded a different result: the corrected temperature record remained strongly correlated with both Earth's length of day and movements of Earth's core throughout the entire temperature data series. The researchers performed robust tests to confirm the statistical significance of their results.
"Our research demonstrates that, for the past 160 years, decadal and longer-period changes in atmospheric temperature correspond to changes in Earth's length of day if we remove the very significant effect of atmospheric warming attributed to the buildup of greenhouse gases due to mankind's enterprise," said Dickey. "Our study implies that human influences on climate during the past 80 years mask the natural balance that exists among Earth's rotation, the core angular momentum and the temperature at Earth's surface."
So what mechanism is driving these correlations? Dickey said scientists aren't sure yet, but she offered some hypotheses.
Since scientists know air temperature can't affect movements of Earth's core or Earth's length of day to the extent observed, one possibility is the movements of Earth's core might disturb Earth's magnetic shielding of charged-particle (i.e., cosmic ray) fluxes that have been hypothesized to affect the formation of clouds. This could affect how much of the sun's energy is reflected back to space and how much is absorbed by our planet. Other possibilities are that some other core process could be having a more indirect effect on climate, or that an external (e.g. solar) process affects the core and climate simultaneously.
Regardless of the eventual connections to be established between the solid Earth and climate, Dickey said the solid Earth's impacts on climate are still dwarfed by the much larger effects of human-produced greenhouse gases. "The solid Earth plays a role, but the ultimate solution to addressing climate change remains in our hands," she concluded.
Study results were published recently in the Journal of Climate.
The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by NASA's Jet Propulsion Laboratory.
Chilly Times for Chinese Dinosaurs: Abundance of Feathered Dinosaurs During Temperate Climate With Harsh Winters
Dinosaurs did not always enjoy mild climates. New findings show that during part of the Early Cretaceous, north-east China had a temperate climate with harsh winters. They explain the abundance of feathered dinosaurs in fossil deposits of that period.
The discovery was made by an international collaboration coordinated by Romain Amiot of the Laboratoire de géologie de Lyon: terre, planètes et environnement (CNRS/ENS de Lyon/Université Lyon 1).
Their work is published in the Proceedings of the National Academy of Sciences.
It has long been thought that the climate of the Mesozoic, the age of the dinosaurs, was generally warm across the planet. However, a recent study challenges this theory. The work focuses on a region of north-east China where the Jehol fauna developed during part of the Early Cretaceous (between 125 and 110 million years ago). The fossils found in this deposit include many dinosaurs covered with filamentous structures similar to bird feathers (such structures can take on various forms, ranging from filaments, down and 'protofeathers' to true feathers). But is this feature due simply to excellent conditions of preservation or to the adaptation of such species to environmental conditions? Since these dinosaurs were unable to fly, several scientists have suggested that their feathers acted as thermal insulation.
A team of paleontologists from France, China, Japan and Thailand examined the issue and tried to determine the temperatures at that time. Teeth and bones from dinosaurs, mammalian reptiles, crocodiles, turtles and freshwater fish from fossil deposits containing the Jehol fauna were collected. This selection of samples was then completed by fossil remains from contemporary deposits in other regions of China, Japan and Thailand. The scientists analyzed the oxygen isotopic composition of each sample. They based their analysis on the principle that the average local air temperature determines the relative quantity of oxygen isotopes contained in the rainwater drunk by the animals. This isotope record is passed on and stored within the bones and teeth of animals as they grow. Since the oxygen contained in the mineralized tissue is preserved during fossilization, the researchers were able to reconstruct the prevailing air temperatures in the environment of Asian dinosaurs during the Early Cretaceous.
The results show that average temperatures in this period of the Early Cretaceous were very similar to those of today at equivalent latitudes (such as the climate in Beijing today). The Jehol fauna therefore lived in a cool temperate climate characterized by harsh winters during which cold-blooded reptiles (turtles and lizards) had to hibernate, whereas the down, feathers and fur of warm-blooded animals (mammals, birds and dinosaurs) enabled them to maintain sustained activity in winter. "These results do not prove in any way that feathers appeared because of their insulating characteristics. They show that feathers would have given the dinosaurs of the Jehol fauna a physiological advantage over their fellow animals with scales," points out Amiot, lead author of the paper and currently a CNRS researcher at the Laboratoire de géologie de Lyon (ENS de Lyon/Université de Lyon 1/CNRS).
This work helps us to better understand the Early Cretaceous period, of which there are few geological records, and sheds new light on existing theories about Earth at the time of the dinosaurs.
The laboratories involved are: Laboratoire de géologie de Lyon: terre, planètes et environnement (CNRS/Université Lyon 1/ENS de Lyon); Laboratoire de géologie de l'École normale supérieure (CNRS/ENS Paris); Institut de physique du globe de Paris (CNRS/UPMC/Université Paris Diderot); and the Institute of Vertebrate Paleontology and Paleoanthropology , Beijing, China.
The Everglades National Park in Florida is home to hundreds of species of native wildlife. It has also become the well-established home of the non-native Burmese python -- known to be a predator of native species. Now scientists, for the first time, have conducted a detailed analysis of the avian component of the python's diet and the negative impact the snakes may have on Florida's native birds, including some endangered species.
The Burmese python (Python molurus bivittatus), native to Southeast Asia, was first recorded in the Everglades in 1979 -- thought to be escaped or discarded pets. Their numbers have since grown, with an estimated breeding population in Florida in the tens of thousands. As researchers investigate the impact of this snake in the Everglades, scientists from the Smithsonian Institution, South Florida Natural Resources Center and the University of Florida examined the snake's predation of the area's birds. They found that birds, including endangered species, accounted for 25 percent of the python's diet in the Everglades.
"These invasive Burmese pythons are particularly hazardous to native bird populations in North America because the birds didn't evolve with this large reptile as a predator," said Carla Dove, ornithologist at the Smithsonian's Feather Identification Lab in the National Museum of Natural History. "Conversely, the python is able to thrive here partly because it has no natural predator to keep its numbers in check."
The scientists collected 343 Burmese pythons in Everglades National Park as part of their study between 2003 and 2008. Eighty-five of these snakes had bird remains in their intestinal tract. From these remains the team identified 25 species of birds by comparing feathers and bone fragments with specimens in the Smithsonian's collection. The results reflected a wide variety of species, from the 5-inch-long house wren to the 4-foot-long great blue heron. Four of the species identified (snowy egret, little blue heron, white ibis and limpkin) are listed as "species of special concern" by the Florida Fish and Wildlife Conservation Commission. The team also identified the remains of a wood stork, which is a federally endangered species.
"These pythons can also inhabit a wide variety of habitats, so their impact is not restricted to just the native species within the Everglades," Dove said. "The python's high reproductive rate, longevity, ability to consume large prey and consumption of bird species are causes for serious conservation and control measures."
The team's findings are published in the scientific journal BioOne, March 2011.
jueves, 10 de marzo de 2011
Concerned archaeologists called today on Egypt’s Prime Minister Essam Sharaf to return police to archaeological sites. The move is required to put an end to illegal excavations and wild looting of storehouses and tombs.
“The desecration of archaeological sites and monuments is not only a huge loss for the people of Egypt on a national, economic, and human level, but is also a loss to all of humanity and to science,” Tarek El Awadi, director of the National Egyptian museum, said in an open letter to Sharaf.
Following the revolution that toppled President Hosni Mubarak last month, a new unprecedented wave of looting and vandalism took place at various sites in Egypt.
“During the revolution of January 25th, the Egyptian Army protected our heritage sites and the Egyptian Museum in Cairo. However, in the last 10 days the army has left these posts because it has other tasks to do,” said Zahi Hawass, who resigned this week as minister of antiquities in protest at the lack of proper action on the looting.
“The group now in charge of the protection of these sites is the Tourist Police, but there are no Tourist Police to do this either,” Hawass said.
In the past few weeks, looters have removed inscribed blocks from tombs at Saqqara, Giza and Abusir, and even tried to cut into pieces a colossal red granite statue of the 19th Dynasty king Ramesses II at the southern quarry of Aswan.
One of the biggest losses is the tomb of the royal scribe Ken Amun in Tell el-Maskhuta, near Ismailia. Dating to the 19th Dynasty B.C (1315-1201 B.C.), the burial is the first ever Ramesside-period tomb uncovered in Lower Egypt.
Discovered last year, the burial featured beautifully decorated walls which are now a lost memory. Sadly, the site has been completely destroyed.
“Everyday, in the morning, I am waiting for news. What has been robbed today? What has been stolen today?” Hawass said. He will remain in his office until the government announce his successor.
Meanwhile, holding together on social networks, Egyptologists and archaeologists have started an international petition campaign to call for the restoration of adequate security to the sites, storehouses, monuments and antiquities of Egypt.
"The situation is certainly quite dire indeed," Andrew Bayuk, who started the petition, told Discovery News.
"This petition is an opportunity for the field of Egyptology to unite for a single purpose, and invite the support of other concerned people throughout the world to make a strong global statement," Bayuk, who created Guardian's Egypt, one of the oldest ancient Egypt website, said.
Photo: Statue of Ramesses II with visible cut marks on the front of the crown. Courtesy of SCA
A brown dwarf, about 75 light-years from Earth, has hit a new low. In fact, its temperature is so low that it is about the same temperature as the cup of tea sitting at my desk. Ladies and gentlemen, meet "CFBDSIR J1458+1013B," the sub-100 degree Celsius (212 F) failed star.*
A group of astronomers headed by Michael Liu, of the University of Hawaii, used the awesome power of adaptive optics on the 10-meter Keck II Telescope on Mauna Kea to probe the very faint infrared signature of this brown dwarf -- which exists as a brown dwarf binary, orbiting with its partner, CFBDSIR J1458+1013A -- revealing that the object may belong to a notoriously rare type of brown dwarf. This object is the faintest brown dwarf spotted by far and it is estimated to be only 6-15 times the mass of Jupiter.
You may have heard brown dwarfs being referred to as "failed stars" as they are not massive enough to support nuclear fusion in their cores, and yet they can't be called "planets" as they don't exhibit chemical differentiation with depth and have convective flows -- a very star-like quality. Therefore, they exist in a stellar hinterland, where they are neither a star or a planet, and yet exhibit characteristics of both.
But astronomers still classify brown dwarfs by their spectral type (a scale of letters assigned to the luminosity of stars), which relates to their temperature. At the lowest, coolest end of the scale, radiating in infrared wavelengths, are the oddball brown dwarfs.
So far, the coolest brown dwarfs observed exist at the lowest end of the scale, with a spectral class of "T." However, there is a theoretical class "Y" that is even cooler than the T-class brown dwarfs -- they are predicted to have a temperature less than 225 degrees Celsius (440 F).
More Like a Planet? More Like a Star?
Although Y-class candidates have been spotted by other instruments, the Keck telescope has put a very tight constraint on the temperature of CFBDSIR J1458+1013B and it looks as if this brown dwarf has more "planet-like" qualities than "star-like" qualities, with a temperature of 97 degrees Celsius (give or take 40 degrees C).
Could CFBDSIR J1458+1013B be the missing link between stars and planets? How can we work out if this object is more like Jupiter, say, or more like the sun?
Usually, water will exist in a gaseous state in brown dwarf atmospheres. But at such low temperatures, it is expected that water in the brown dwarf's atmosphere will condense to form clouds. Although it is hard to detect condensing water in this brown dwarf's atmosphere, it is certainly a prime "Y" class candidate.
Regardless, CFBDSIR J1458+1013B is the coolest brown dwarf in the cosmic neighborhood and it could help us understand the point at which a star becomes a star and a planet becomes a planet.
*Although brown dwarfs are known as "failed stars," I like to refer to them as "overachieving planets." Whoever said that becoming a star was the pinnacle of stellar living anyway?
Image credit: NASA, ESA and G. Bacon (STScI)
A circular depression deep in the Democratic Republic of the Congo (DRC) has been confirmed as the first known impact crater in central Africa, a new study says. The find brings the number of known meteor craters on Earth to 182.
The so-called Luizi structure was first described in a German geological report from 1919. But without further fieldwork, it was impossible to say for sure that the 10.5-mile-wide (17-kilometer-wide) feature had been made by a meteor impact.
On other planets, such as Mercury and Mars, it's easier to identify impact craters based only on their shapes, since these worlds no longer have geologic forces making major changes to their surfaces.
But on Earth, many older craters have likely been erased by tectonic activity or erosion, while others are so covered with dense vegetation or sediments, like Luizi, that they're almost impossible to spot without satellites.
What's more, the crater-like structures we do see may have been made by volcanoes, collapsed underground chambers, and other forces that have nothing to do with impacts, said study leader Ludovic Ferrière, curator of the rock collection at the Natural History Museum of Vienna in Austria.
"On Earth, to confirm it's an impact, you have to go in the field because you need evidence of high pressures and temperatures," Ferrière said.
Crater Expedition Had Brushes With Snakes, Poachers
The researcher first became interested in the Luizi structure after seeing satellite pictures published in the 1990s.
By studying the available satellite data, Ferrière and colleagues estimated that the structure has an elevated rim about 1,148 feet (350 meters) high, as well as an interior ring and a central depression.
But to truly confirm Luizi as an impact crater, the researchers had to mount an expedition to the politically tumultuous DRC.
"I was working for a year just to find a contact there, because you need a local person to help you find your way around," Ferrière said.
With funding from the National Geographic Society/Waitt Foundation program, Ferrière—then a postdoc at the University of Western Ontario in Canada—visited the crater site in June 2010 with colleagues from the University of Lubumbashi.
"I flew direct to Lubumbashi, the second largest city in the DRC. From there we had to drive from the city to the crater," he said.
"I had looked at maps and planned a route before I left. But when I got there, my contact told me there is no bridge across part of my intended path. We had to take some crazy gravel roads with big potholes inside. These are not good roads to drive on, even with a four-wheel-drive car."
The team set up camp in a small village about 8 miles (13 kilometers) from the crater rim, recruiting two local guides/porters and a soldier to help them safely navigate the wild terrain.
"The crater is in a national park, and I thought it would be like the jungles of South America," Ferrière said. "Instead it was a tree savanna—a big plataeu with dry grass. The grass was sometimes more than a meter [3.2 feet] high."
Standing on the rim of the Luizi structure, Ferrière could see skinny trees that seemed to fill the depression, with the crater's distant edge rising like small hills.
Despite the remote, wooded terrain, "we saw no large animals, only snakes. But we did see a lot of remnants of poachers. Sometimes we'd come to a site and the doused fires were still hot."
Congo Rocks Had a Shock
Ferrière's team spent about a week at the crater collecting samples, which were sent back to the lab in Canada for analysis.
"I found so-called shatter cones, which are features in the rock only found in impact structures," he said. The nested, conical shapes in such features are evidence that the bedrock has been exposed to extreme pressure from a shock wave.
The crater rocks also contained an abundance of shocked quartz, a version of the mineral known to form only from impacts or nuclear blasts, Ferrière said.
"Everybody will believe me now, I think, that this is an impact site."
The scientists think the Luizi crater was made by a meteor more than 0.6 mile (a kilometer) wide that slammed into what is now the DRC at about 45,000 miles (72,000 kilometers) an hour.
For now it's unclear how old the crater is—the scientists can say only that the affected rocks are about 575 million years old, "but we know it's younger than that, because the rocks have been excavated," Ferrière said.
"It would be nice to do more fieldwork, because the shape of the structure with this inner ring can tell us about the exact formation process involved," he added. In the meantime, the researcher will continue to study the rock samples, now housed at the Vienna museum.
"There is still a lot to discover" about Luizi, he said.
The search for life in the solar system, whether in rocks from Mars or on a Jovian moon, tops the wish list of a panel of space scientists convened by the National Research Council. Mindful of shrinking budgets, the panel has issued hard-nosed recommendations that identify which planetary science missions NASA should fly in the decade beginning 2013. Even some top-rated missions should be either deferred or outright canceled if their estimated costs can’t be significantly cut, the panel says in a report released March 7.
Among its big missions, the panel says, NASA should give highest priority to the Mars Astrobiology Explorer-Cacher. This project would be the first of three missions designed to collect Martian samples and bring them to Earth for analysis of any evidence of life forms. But the panel of space scientists recommends that the mission should go forward only if NASA’s cost can be limited to $2.5 billion; $1 billion less than the project’s estimated price tag in fiscal year 2015 dollars (adjusted for inflation). The European Space Agency and NASA, which will jointly run the mission, should work together to reduce the high cost, the report suggests. One possibility is to include one large robot instead of two.
“I’m ready to hit the ground running with Europe to see if we can do something with that first priority,” says Ed Weiler, NASA’s associate administrator for science in Washington, D.C.
NASA’s Jupiter Europa Orbiter also received a nod from the panel, which ranked the mission as the second-highest priority among large projects. The craft would carry a suite of instruments to determine if Jupiter’s moon Europa has an ocean — a possible haven for life — buried beneath its icy surface, as many scientists suspect. But the panel says the mission should fly only if the project’s current estimated cost of $4.7 billion is reduced and if NASA increases its planetary science budget. The panel did not say specifically how much to cut from the Europa mission in order to maintain funding of other projects, but did spell out a 5 percent boost to NASA’s planetary science research funding compared with fiscal year 2011. The panel also recommends that the planetary science budget should remain 1.5 percent above inflation for the remainder of the decade.
Exploring the structure, composition and atmosphere of Uranus with an orbiter and probe also earned a high mark from the panel, which rated the project third among NASA’s large missions. But the panel recommends the mission be reduced in scope or canceled if it rises above its estimated $2.7 billion cost.
A new study demonstrates that specific traits that distinguish humans from their closest living relatives -- chimpanzees, with whom we share 96 percent of our DNA -- can be attributed to the loss of chunks of DNA that control when and where certain genes are turned on. The finding mirrors accumulating evidence from other species that changes to regulatory regions of DNA -- rather than to the genes themselves -- underlie many of the new features that organisms acquire through evolution.
Seeking specific genetic changes that might be responsible for the evolution of uniquely human traits, Howard Hughes Medical Institute investigator David Kingsley and colleagues at Stanford University scanned the human genome for features that set us apart from other mammals. The team found 510 segments that are present in chimps and other animals but missing from the human genome. Only one of the missing segments would actually disrupt a gene; the remaining 509 affect the DNA that surrounds genes, where regulatory sequences lie.
Careful analysis of a handful of these segments demonstrated that loss of regulatory DNA could explain how humans developed some features not found in other animals -- such as big brains -- as well as how they lost features common in other species, such as sensory whiskers and spiny penises. Their findings are published in the March 10, 2011, issue of the journal Nature.
Genes -- segments of DNA that carry the blueprints for proteins -- make up less than two percent of the human genome. Hidden within the remainder of our more than three billion base pairs of DNA are regulatory sequences that control when and where genes are expressed. Direct alterations to a gene can have dramatic effects, sometimes killing an organism or rendering it sterile. "In contrast, if you alter the way [a gene] turns on or off at a particular place in development, that can have a very large effect on a particular structure, but still preserve the other functions of the gene," Kingsley says. "That tends to be the sort of alternation that's favored when a new trait is evolving."
Kingsley's previous work with stickleback fish, a small spiny fish whose recent and rapid adaptation to a wide range of aquatic environments has made it ideal for evolutionary studies, have shown time and again that changes in regulatory DNA can have profound effects on an organism's traits. So when Kingsley and his colleagues searched for regions of the genome common to chimps, macaques, and mice but missing in the human genome, they weren't surprised that the sequence differences they found were almost exclusively outside of genes.
Collaborating with computational biologist Gill Bejerano's lab at Stanford, the team pinpointed 510 genetic sequences that appear in the genomes of chimps and other animals, but are "surprisingly missing" from the human genome, Kingsley says. To narrow the list so that they could focus on the changes most likely to have altered when and where particular genes were expressed, the researchers conducted a computer analysis to identify deletions that were clustered around particular genes. "We saw more changes than you would expect near genes involved in steroid hormone signaling," Kingsley says. A number of deletions also appeared near genes involved in neural development, their analysis revealed.
But technology could only take the team so far. To zero in on specific deletions that might control human traits, the team relied on manpower: neuroscientists, physical anthropologists, developmental geneticists, and more. "We had a team of interested graduate students, postdocs, and developmental biologists poring through this list," Kingsley says. The team searched for sequences near genes known to play key roles in development, especially those known to control traits that differ between humans and other animals. "It was a fun detective hunt that led to lots of interesting discussions," he says.
The team came up with a couple dozen deletions near genes they suspected might be involved in the evolution of particular human traits. But the researchers still didn't know the normal functional roles of the missing sequences. So Kingsley and his colleagues isolated those genetic sequences from organisms that still had them (chimps or mice), attached the sequences to a reporter gene that produces a simple blue color reaction in living cells, and injected the resulting sequences into fertilized mouse eggs. By monitoring the blue color reaction in developing mice, they could see exactly where and when the sequence was turning on gene expression during embryonic or postnatal development. This gave them a way to link "the biology of the gene, the molecular change that had happened in humans, and the specific anatomical place where it really was expressed during normal development," Kingsley explains.
These experiments highlighted two segments of DNA that humans lack, but that appear to play a particularly important role in development of mice and other non-human mammals. The first is a segment of DNA that, in most animals, occurs near the gene that codes for the androgen receptor, which is associated with a variety of male-specific traits. "Males have beards, females don't," Kingsley says. "That's an example of an androgen receptor-dependent process." When the researchers inserted this sequence into mouse eggs, "what we got were blue sensory whiskers and blue genitalia," Kingsley says, indicating that when present, the sequence causes the androgen receptor to be produced in those regions.
Tracing the expression of the protein through development, Kingsley and his colleagues concluded that the sequence contributes to the development of sensory whiskers found on the faces of many mammals, and prickly surface spines found on the penises of mice and many non-human primates. Previous studies show that complete inactivation of the androgen receptor gene lead to defects in whiskers and failure to form penile spines. Although humans still retain the androgen receptor gene, the loss of regulatory information for expression in whiskers and spines could help explain two human-specific anatomical traits: absence of sensory whiskers and lack of spines on human penises. Loss of penile spines is one of several traits thought to be related to evolution of pair-bonding and monogamy in the human lineage.
The second segment of regulatory DNA they tested appears, in non-humans, near a gene called GADD45g. GADD45g normally reins in cell growth. In fact, Kingsley said, "if the gene is missing entirely, unchecked cell growth can cause pituitary tumors." When they injected the sequence into mouse eggs, they found the tell-tale blue color in a key growth layer of the developing brain -- indicating that in most animals, the regulatory sequence that has disappeared in humans restricts brain growth.
The study describes some of the changes that have helped make humans human, but there are likely to be many more, Kingsley says. "By simply changing a single gene like GADD45g you're not going to be able to explain all of human brain evolution."
Still, he adds, the study shows that "it's now possible to begin identifying some of the particular molecular changes that contribute to the evolution of human traits." Human-specific traits include not only anatomical and physiological differences, but also differences in our susceptibility to many diseases, such as arthritis, cancer, malaria, HIV, Alzheimer's, and Parkinson's. "We think that the same sorts of lists and approaches will eventually help illuminate human disease susceptibilities as well," he says. "It's a great time to be studying not only where we came from, but also how our genetic history shapes many aspects of current human biology."
Heat output from the south polar region of Saturn's moon Enceladus is much greater than was previously thought possible, according to a new analysis of data collected by NASA's Cassini spacecraft.
The study was published in the Journal of Geophysical Research on March 4.
Data from Cassini's composite infrared spectrometer of Enceladus' south polar terrain, which is marked by linear fissures, indicate that the internal heat-generated power is about 15.8 gigawatts, approximately 2.6 times the power output of all the hot springs in the Yellowstone region, or comparable to 20 coal-fueled power stations. This is more than an order of magnitude higher than scientists had predicted, according to Carly Howett, the lead author of study, who is a postdoctoral researcher at Southwest Research Institute in Boulder, Colo., and a composite infrared spectrometer science team member.
"The mechanism capable of producing the much higher observed internal power remains a mystery and challenges the currently proposed models of long-term heat production," said Howett.
It has been known since 2005 that Enceladus' south polar terrain is geologically active and the activity is centered on four roughly parallel linear trenches, 130 kilometers (80 miles) long and about 2 kilometers (1 mile) wide, informally known as the "tiger stripes." Cassini also found that these fissures eject great plumes of ice particles and water vapor continually into space. These trenches have elevated temperatures due to heat leaking out of Enceladus' interior.
A 2007 study predicted the internal heat of Enceladus, if principally generated by tidal forces arising from the orbital resonance between Enceladus and another moon, Dione, could be no greater than 1.1 gigawatts averaged over the long term. Heating from natural radioactivity inside Enceladus would add another 0.3 gigawatts.
The latest analysis, which also involved the composite infrared spectrometer team members John Spencer at Southwest Research Institute, and John Pearl and Marcia Segura at NASA's Goddard Space Flight Center in Greenbelt, Md., uses observations taken in 2008, which cover the entire south polar terrain. They constrained Enceladus' surface temperatures to determine the region's surprisingly high output.
A possible explanation of the high heat flow observed is that Enceladus' orbital relationship to Saturn and Dione changes with time, allowing periods of more intensive tidal heating, separated by more quiescent periods. This means Cassini might be lucky enough to be seeing Enceladus when it's unusually active.
The new, higher heat flow determination makes it even more likely that liquid water exists below Enceladus' surface, Howett noted.
Recently, scientists studying ice particles ejected from the plumes discovered that some of the particles are salt-rich, and are probably frozen droplets from a saltwater ocean in contact with Enceladus' mineral-rich rocky core. The presence of a subsurface ocean, or perhaps a south polar sea between the moon's outer ice shell and its rocky interior would increase the efficiency of the tidal heating by allowing greater tidal distortions of the ice shell.
"The possibility of liquid water, a tidal energy source and the observation of organic (carbon-rich) chemicals in the plume of Enceladus make the satellite a site of strong astrobiological interest," Howett said.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA's Jet Propulsion Laboratory, Pasadena, Calif., a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The CIRS team is based at NASA's Goddard Space Flight Center in Greenbelt, Md., where the instrument was built.
The brain is a black box. A complex circuitry of neurons fires information through channels, much like the inner workings of a computer chip. But while computer processors are regimented with the deft economy of an assembly line, neural circuits are impenetrable masses. Think tumbleweed.
Researchers in Harvard Medical School's Department of Neurobiology have developed a technique for unraveling these masses. Through a combination of microscopy platforms, researchers can crawl through the individual connections composing a neural network, much as Google crawls Web links.
"The questions that such a technique enables us to address are too numerous even to list," said Clay Reid, HMS professor of neurobiology and senior author on a paper reporting the findings in the March 10 edition of Nature.
The cerebral cortex is arguably the most important part of the mammalian brain. It processes sensory input, reasoning and, some say, even free will. For the past century, researchers have understood the broad outline of cerebral cortex anatomy. In the past decade, imaging technologies have allowed us to see neurons at work within a cortical circuit, to watch the brain process information.
But while these platforms can show us what a circuit does, they don't show us how it operates.
For many years, Reid's lab has been studying the cerebral cortex, adapting ways to hone the detail with which we can view the brain at work. Recently they and others have succeeded in isolating the activities of individual neurons, watching them fire in response to external stimuli.
The ultimate prize, however, would be to get inside a single cortical circuit and probe the architecture of its wiring.
Just one of these circuits, however, contains between 10,000 and 100,000 neurons, each of which makes about 10,000 interconnections, totaling upwards of 1 billion connections -- all within a single circuit. "This is a radically hard problem to address," Reid said.
Reid's team, which included Davi Bock, then a graduate student, and postdoctoral researcher Wei-Chung Allen Lee, embarked on a two-part study of the pinpoint-sized region of a mouse brain that is involved in processing vision. They first injected the brain with dyes that flashed whenever specific neurons fired and recorded the firings using a laser-scanning microscope. They then conducted a large anatomy experiment, using electron microscopy to see the same neurons and hundreds of others with nanometer resolution.
Using a new imaging system they developed, the team recorded more than 3 million high-resolution images. They sent them to the Pittsburgh Supercomputing Center at Carnegie Mellon University, where researchers stitched them into 3-D images. Using the resulting images, Bock, Lee and laboratory technician Hyon Suk Kim selected 10 individual neurons and painstakingly traced many of their connections, crawling through the brain's dense thicket to create a partial wiring diagram.
This model also yielded some interesting insights into how the brain functions. Reid's group found that neurons tasked with suppressing brain activity seem to be randomly wired, putting the lid on local groups of neurons all at once rather than picking and choosing. Such findings are important because many neurological conditions, such as epilepsy, are the result of neural inhibition gone awry.
"This is just the iceberg's tip," said Reid. "Within ten years I'm convinced we'll be imaging the activity of thousands of neurons in a living brain. In a visual circuit, we'll interpret the data to reconstruct what an animal actually sees. By that time, with the anatomical imaging, we'll also know how it's all wired together."
For now, Reid and his colleagues are working to scale up this platform to generate larger data sets.
"How the brain works is one of the greatest mysteries in nature," Reid added, "and this research presents a new and powerful way for us to explore that mystery."
This research was funded by the Center for Brain Science at Harvard University, Microsoft Research, and the NIH though the National Eye Institute. Researchers report no conflicts of interest.
viernes, 4 de marzo de 2011
A headless metal warrior stomps towards you, shooting. Fortunately, you've been training for a marathon and easily jet off to safety down an alleyway. But wait -– now a metal cheeta-bot is after you, racing faster than your puny legs can go. As the space between you and the galloping beast closes, you round a corner, see a door and dive through. It slams behind you. As you freeze, holding your breath, the robotic cat passes by outside with a wake of metallic echoes.
Relieved, you exhale into the dark. A fatal mistake -– outside, another robot has detected your breath and alerted the enemy to your location …
Waking up from this nightmare is a way to save yourself, for now, but in fact all three 'terror' bots it featured are based on actual prototypes being developed in California and Boston (though not with directly malicious intentions). Here's an introduction to the motley three.
A headless humanoid is being built by Boston Dynamics. Called Atlas, it has is a heel-to-toe gait. The designers want Atlas to be able to navigate over rough terrain as well as a human can, by resorting to a crawl or turning itself sideways as the situation necessitates. He (she?) also stays upright when pushed and can currently travel at 3.2 miles per hour. Atlas is the improved version of an earlier robo-person, Petman, that was designed to test the Army's chemical weapons suits, while mimicking human movement and physiology. Boston Dynamics recently won DARPA contracts to further develop Atlas and another robot named Cheetah.
DARPA asked Boston Dynamics to build this robot-cat with a flexible spine, movable head and possibly even a tail. According to this IEEE Spectrum blog, the designers says Cheetah will sprint "faster than any existing legged robot and faster than the fastest human runners.” More than a speedy quadruped, Cheetah also has cat-like agility, able to turn corners and zig-zag with ease, as well as making lightning fast starts and stops.
A mini-surveillance robot more like Johnny 5 than a wildcat, the Cougar 20-H can park itself outside a building and detect activity inside from 65 feet away. The Army-funded rover, built by Orange County, Calif.-based TiaLinx, uses a low-power radar mounted on a tripod that can detect heartbeats and even breathing. As pointed out in Wired's Danger Room blog, this might actually make the Cougar 20-H well suited for search and rescue missions or for monitoring borders, since it can detect people through walls and underground.
Photo: Boston Dynamics
This winter an alarmingly high number of young bottlenose dolphins in the Gulf of Mexico (map) have been washing up dead on U.S. shores, government scientists report.
The reason for the die-off is a mystery, and experts are urging caution in drawing any connections to last year's BP oil spill.
"Everybody wants to jump to that conclusion ... but at this point in time, it's too early to tell," said Blair Mase, coordinator of the Southeast Marine Mammal Stranding Network of the National Atmospheric and Oceanic Administration (NOAA).
Since January 1, 80 dead dolphins have been discovered along the coasts of Louisiana, Mississippi, Alabama, and Florida, according to the latest NOAA figures.
Forty-two of the dead were calves. Most of the juvenile dolphins are washing up in Mississippi and Alabama, because dolphins typically give birth and raise calves along the shallow shores of those states.
The normal gestation period for the dolphins is one year, and mothers usually give birth in March and April, so scientists think the affected calves are either being aborted, stillborn, or born prematurely.
"That's one part of the investigation that we're going to be looking at very carefully," Mase said.
"We'll methodically score each animal that has come ashore to determine if, in fact, it was an aborted calf or an animal born alive."
BP Oil Spill "a Factor We Need to Consider"
Dolphin die-offs—which scientists call unusual mortality events—occur every few years. But this one stands out, because young dolphins appear to be hardest hit, marine biologist Moby Solangi said.
"Usually in a stranding, you have a mixture of animals—males, females, adults, calves—but this one is distortedly focused on neonates," said Solangi, director of the Institute for Marine Mammal Studies (IMMS) in Gulfport, Mississippi, which is helping to investigate the deaths.
Also unusual: Only dolphins appear to be affected so far. No mass deaths of turtles, fish, or birds have been reported for this die-off.
Known causes of dolphin die-offs include unusually cold waters, ocean biotoxins, and diseases.
NOAA's Mase said scientists are investigating all of these factors and are not ruling out a possible connection to the BP oil spill.
"It's something that we are including in our investigation," Mase said.
IMMS's Solangi agreed that the BP oil spill "is a factor that we need to consider."
"The oil spill lasted several months, and it covered tens of thousands of square miles and much of the habitat of these animals."
IMMS scientists are currently performing necropsies on the dead dolphins to try to determine causes of death. The process—including analyzing tissue samples for signs of diseases, viral infections, and toxins—could take several weeks or months, Solangi said.
Oil Link Tough to Prove
While a link between last year's BP oil spill and this year's dolphin deaths is possible, it could be very difficult to prove, said Craig Matkin, a marine biologist at the North Gulf Oceanic Society in Alaska.
Matkin co-authored a study in 2008 that looked at the effects of the 1989 Exxon Valdez oil spill on killer whale populations in Alaska's Prince William Sound.
"I'm not overly optimistic that they're going to be able to find a link," he said.
One reason is that—unlike other environmental toxins, such as the pesticide DDT—the hydrocarbon molecules in oil are quickly processed by the body and do not persist in tissues, Matkin explained.
Scientists also don't have a good idea of how the spill might have affected dolphins still in the womb.
Oil is thought to affect marine animals through inhalation or direct and indirect ingestion—for example, by eating tainted fish. But the calves now showing up dead may not have even been conceived before or during the worst weeks of the spill and thus were not exposed to the oil directly.
Dolphin Die-offs Largely Cold Cases
In his 2008 study, Matkin's team concluded that the Exxon Valdez spill affected Alaskan killer whale populations for decades after the event. After inhaling oil vapors or eating oil-coated seals, for example, the whales experienced everything from "mild irritation" to instant death, the study days.
It's unknown how the 1989 spill affected calves. Killer whales tend to give birth in deep water, so dead calves are much less likely to wash ashore.
Matkin pointed out key differences between the two events.
"This is just not the same kind of situation," he said. "We were following individual animals for a period of time before the [Exxon Valdez] spill, so we knew who was missing, down to the individual.
"It's very different when you have a bunch of unknown animals stranded on a beach and you don't know anything about their history."
NOAA's Mase said it's possible that no satisfactory answer will ever be found for the dolphin-baby die-off.
"There have been 14 [unusual mortality events] since 1990," she said. "And of those 14, we've only been able to determine the causes for 6."
On February 14 the sun erupted with the largest solar flare seen in four years—big enough to interfere with radio communications and GPS signals for airplanes on long-distance flights.
As solar storms go, the Valentine's Day flare was actually modest. But the burst of activity is only the start of the upcoming solar maximum, due to peak in the next couple of years.
"The sun has an activity cycle, much like hurricane season," Tom Bogdan, director of the Space Weather Prediction Center in Boulder, Colorado, said earlier this month at a meeting of the American Association for the Advancement of Science in Washington, D.C.
"It's been hibernating for four or five years, not doing much of anything." Now the sun is waking up, and even though the upcoming solar maximum may see a record low in the overall amount of activity, the individual events could be very powerful.
In fact, the biggest solar storm on record happened in 1859, during a solar maximum about the same size as the one we're entering, according to NASA.
That storm has been dubbed the Carrington Event, after British astronomer Richard Carrington, who witnessed the megaflare and was the first to realize the link between activity on the sun and geomagnetic disturbances on Earth.
During the Carrington Event, northern lights were reported as far south as Cuba and Honolulu, while southern lights were seen as far north as Santiago, Chile.
The flares were so powerful that "people in the northeastern U.S. could read newspaper print just from the light of the aurora," Daniel Baker, of the University of Colorado's Laboratory for Atmospheric and Space Physics, said at a geophysics meeting last December.
In addition, the geomagnetic disturbances were strong enough that U.S. telegraph operators reported sparks leaping from their equipment—some bad enough to set fires, said Ed Cliver, a space physicist at the U.S. Air Force Research Laboratory in Bedford, Massachusetts.
In 1859, such reports were mostly curiosities. But if something similar happened today, the world's high-tech infrastructure could grind to a halt.
"What's at stake," the Space Weather Prediction Center's Bogdan said, "are the advanced technologies that underlie virtually every aspect of our lives."
Solar Flare Would Rupture Earth's "Cyber Cocoon"
To begin with, the University of Colorado's Baker said, electrical disturbances as strong as those that took down telegraph machines—"the Internet of the era"—would be far more disruptive. Solar storms aimed at Earth come in three stages, not all of which occur in any given storm.
First, high-energy sunlight, mostly x-rays and ultraviolet light, ionizes Earth's upper atmosphere, interfering with radio communications. Next comes a radiation storm, potentially dangerous to unprotected astronauts.
Finally comes a coronal mass ejection, or CME, a slower moving cloud of charged particles that can take several days to reach Earth's atmosphere. When a CME hits, the solar particles can interact with Earth's magnetic field to produce powerful electromagnetic fluctuations. (Related: "Magnetic-Shield Cracks Found; Big Solar Storms Expected.")
"We live in a cyber cocoon enveloping the Earth," Baker said. "Imagine what the consequences might be."
Of particular concern are disruptions to global positioning systems (GPS), which have become ubiquitous in cell phones, airplanes, and automobiles, Baker said. A $13 billion business in 2003, the GPS industry is predicted to grow to nearly $1 trillion by 2017.
In addition, Baker said, satellite communications—also essential to many daily activities—would be at risk from solar storms.
"Every time you purchase a gallon of gas with your credit card, that's a satellite transaction," he said.
But the big fear is what might happen to the electrical grid, since power surges caused by solar particles could blow out giant transformers. Such transformers can take a long time to replace, especially if hundreds are destroyed at once, said Baker, who is a co-author of a National Research Council report on solar-storm risks.
The U.S. Air Force Research Laboratory's Cliver agrees: "They don't have a lot of these on the shelf," he said.
The eastern half of the U.S. is particularly vulnerable, because the power infrastructure is highly interconnected, so failures could easily cascade like chains of dominoes.
"Imagine large cities without power for a week, a month, or a year," Baker said. "The losses could be $1 to $2 trillion, and the effects could be felt for years."
Even if the latest solar maximum doesn't bring a Carrington-level event, smaller storms have been known to affect power and communications.
The "Halloween storms" of 2003, for instance, interfered with satellite communications, produced a brief power outage in Sweden, and lighted up the skies with ghostly auroras as far south as Florida and Texas.
Buffing Up Space-Weather Predictions
One solution is to rebuild the aging power grid to be less vulnerable to solar disruptions.
Another is better forecasting. Scientists using the new Solar Dynamics Observatory spacecraft are hoping to get a better understanding of how the sun behaves as it moves deeper into its next maximum and begins generating bigger storms.
These studies may help scientists predict when and where solar flares might appear and whether a given storm is pointed at Earth.
"Improved predictions will provide more accurate forecasts, so [officials] can take mitigating actions," said Rodney Viereck, a physicist at the Space Weather Prediction Center.
Even now, the center's Bogdan said, the most damaging emissions from big storms travel slowly enough to be detected by sun-watching satellites well before the particles strike Earth. "That gives us [about] 20 hours to determine what actions we need to take," Viereck said.
In a pinch, power companies could protect valuable transformers by taking them offline before the storm strikes. That would produce local blackouts, but they wouldn't last for long.
"The good news is that these storms tend to pass after a couple of hours," Bogdan added.
Meanwhile, scientists are scrambling to learn everything they can about the sun in an effort to produce even longer-range forecasts.
According to Vierick, space-weather predictions have some catching up to do: "We're back where weather forecasters were 50 years ago."
Memories fade with time, often to the annoyance of those who can’t recall important details. But scientists have now found a way to boost the recall of memories even after they’ve started to fade. Unfortunately, the method involves injecting an engineered virus directly into the brain, so those of us who are bad with names may want to wait a bit for the technique to be refined.
The work was done in rats, and the memories in question are associations between a specific taste — saccharine, for example — and an unpleasant stimulus, caused by injection of a nausea-inducing drug (the approach is called “conditioned taste aversion”). Unless the unpleasant association is reinforced, the memories will slowly fade with time, although the aversion doesn’t disappear entirely during the two-week period that the authors were looking at.
Two years ago, the same authors found that it was possible to radically accelerate this fading. By injecting a chemical that blocked a specific brain enzyme (protein kinase M ζ), the authors caused the rats to act as if they had never experienced the nausea, even if the memory manipulation took place 25 days after the conditioning. Most chemicals that interfere with memories tend to prevent them from being consolidated for long-term storage, but this chemical seemed to work even after the memory was firmly in place.
That’s potentially helpful, since some people have formed negative associations with harmless or even helpful items. Still, for most of us, it would be nice to think that fading memories could be resuscitated. Apparently, they can. The researchers have now done what’s effectively the converse experiment, and increased the activity of protein kinase M ζ. They did this by engineering a virus to express the gene for the kinase, and then infected specific areas of the brain involved in memory. All the infected cells had additional copies of the gene, and thus made more of its product.
The virus had exactly the effect that the authors would presumably have predicted. The virus was injected a week after the rats were given the aversion conditioning, when the memory would already be starting to fade, and the memory tests were done a week after that, yet rats showed a significantly improved retention of their memories. As the authors point out, the engineered virus boosted a memory that was formed before it was even present.
The memory molecule, PKMzeta, overexpressed in rat neurons. Red (left) shows PKMzeta while green (middle) is a fluorescent protein that shows nerve cells have been infected by viruses engineered to boost the memory molecule. Yellow (right) shows both the memory molecule and green fluorescent protein only overexpress at certain locations in the neuron. Weizmann Institute of Science/Science
Actually, you can make that memories, plural. The authors trained rats to avoid both saccharine and salty liquids over the course of three days, and then injected the virus a week after the last training. The memories of both of these trainings were enhanced by the presence of the viral protein kinase M ζ gene.
The authors can’t tell exactly what protein kinase M ζ is doing to increase the recall of memories, and suggest it could be either enhancing the association between taste and the unpleasant experience, or simply enhancing recall in general. Although they don’t mention it, their findings may also be limited to specific classes of memories, like the associations examined here.
That latter point makes the last sentence of the paper a bit over the top, as the authors suggest that a chemical that enhances protein kinase M ζ activity might make for a good treatment for memory disorders like amnesia and age-related decline. Until we have a clearer sense of how many types of memories it works for, that’s a bit premature. Fortunately, there are lots of ways to test the recall abilities of animals, many of which don’t involve negative associations. Hopefully, testing of the virus’ more general impact on memory is already underway.
Image: HIV (green dots), a member of the lentivirus genus. (C. Goldsmith/P. Feorino/E. L. Palmer/W. R. McManus/CDC)
The U.S. Air Force’s most mysterious spacecraft is headed back into orbit after a four-month hiatus. The second copy of the Boeing-built X-37 robotic space plane is slated for launch, atop an Atlas V rocket, from Cape Canaveral in Florida sometime on Friday. Forecasts of bad weather could push the launch to Saturday.
In any event, the blast-off is sure to revive speculation regarding the curious, 29-foot-long spacecraft that lands like an airplane — just like a miniature, unmanned space shuttle.
Nearly a year after the first X-37B launched on its 225-day, orbit-hopping inaugural mission, nobody outside of the Air Force knows exactly what the X-37 is for. That ambiguity has even sparked a minor space race as Russia and China at least threaten to build similar vehicles.
In the wake of the first X-37’s April launch, analysts listed all the things the X-37 is theoretically capable of. It could be a commando transport, a bomber or an orbital spy. It could launch, repair or reposition U.S. satellites in low orbit. It could sneak up and disable or steal enemy satellites. Its pickup-bed-sized payload bay is particularly enticing to observers.
“You can put sensors in there, satellites in there,” said Eric Sterner, from The Marshall Institute. “You could stick munitions in there, provided they exist.”
“I applaud the ingenuity and innovation of some reports,” Richard McKinney, the deputy undersecretary of the Air Force for space programs, joked during a December press conference. He insisted the 5-ton spacebot merely represents a “capability for a reusable and more effective way to test technology in space and return it for examination.”
“This is a test vehicle … pure and simple,” McKinney said.
But McKinney wouldn’t say what technologies the X-37 might be testing, and why the Air Force seems so attached to the idea of a self-landing, airplane-style space vehicle. After all, with the extra mass of its wings and landing gear, in some ways the X-37 is actually at a disadvantage compared to disposable spacecraft.
“Building this return capability into the space plane adds tons of extra mass compared to maneuvering spacecraft that are not designed to return to Earth,” Laura Grego and David Wright from the nonprofit Union of Concerned Scientists explained in a blog post. “That large mass penalty makes it more difficult and expensive to get a space plane and its payload into orbit and reduces the amount of maneuvering that it can do with a given amount of fuel.”
Everything the X-37 can apparently do, simpler spacecraft could do better and cheaper, Grego and Wright claimed. Even retrieving experimental items from space is better achieved using a simple capsule and parachute, they insisted.
Despite these criticisms, the Air Force is “really at the beginning of it” with the X-37B, McKinney crowed. The diminutive space bots are likely to stay very busy in coming years, leaving just two possible explanations.
One, the Air Force is stupid and doesn’t realize the X-37 is a second-rate vehicle for mucking about in space.
Or two, the X-37 is capable of something — or a mix of things — we outsiders haven’t yet imagined. Russia and China sure think so.
Scientists have found that calcium, aluminum-rich inclusions (CAIs), some of the oldest objects in the solar system, formed far away from our sun and then later fell back into the mid-plane of the solar system. The findings may lead to a greater understanding of how our solar system and possibly other solar systems formed and evolved.
CAIs, roughly millimeter- to centimeter in size, are believed to have formed very early in the evolution of the solar system and had contact with nebular gas, either as solid condensates or as molten droplets. Relative to planetary materials, CAIs are enriched with the lightest oxygen isotope and are believed to record the oxygen composition of solar nebular gas where they grew. CAIs, at 4.57 billion years old, are millions of years older than more modern objects in the solar system, such as planets, which formed about 10-50 million years after CAIs.
Using Lawrence Livermore's NanoSIMS (nanometer-scale secondary-ion mass spectrometer) -- an instrument that can analyze samples with nanometer-scale spatial resolution -- LLNL scientists in conjunction with NASA Johnson Space Center, University of California, Berkeley and the University of Chicago measured the concentrations of oxygen isotopes found in the CAIs.
In the recent research, the team studied a specific CAI found in a piece of the Allende meteorite. Allende is the largest carbonaceous chondrite meteorite ever found on Earth. It fell to the ground in 1969 over the Mexican state of Chihuahua and is notable for possessing abundant CAIs.
Their findings imply that CAIs formed from several oxygen reservoirs, likely located in distinct regions of the solar nebula. CAIs travelled within the nebula by lofting outward away from the sun and then later falling back into the mid-plane of the solar system or by spiraling through shock waves around the sun.
Through oxygen isotopic analysis, the team found that rims surrounding the CAI show that late in the CAI's evolution, it was in a nebular environment distinct from where it originated and closer in composition to the environment in which the building materials of the terrestrial planets formed.
"Allende is this very unusual meteorite with all these wonderful inclusions (CAIs)," said Ian Hutcheon, one of the LLNL scientists on the team. "The isotopic measurements indicate that this CAI was transported among several different nebular oxygen isotopic reservoirs, arguably as it passed through into various regions of the protoplanetary disk."
A protoplanetary disk is an area of dense gas surrounding a newly formed star. In this case, the CAI formed when our star was quite young.
"It is particularly interesting in understanding the formation and dynamics of our solar system's protoplanetary disk (and protoplanetary disks in general)," said Justin Simon of NASA Johnson Space Center and lead author of a paper appearing in the March 4 issue of the journal Science.
The new observations, "support early and short-lived fluctuations of the environment in which CAIs formed, either due to transport of the CAIs themselves to distinct regions of the solar nebula or because of varying gas composition near the proto-sun," Hutcheon said.
Other Livermore researchers include Jennifer Matzel, Erick Ramon and Peter Weber.