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嘿嘿嘿~大家慢慢看哇哈哈~
【速度】
【time one】
A 2.1 Billion-Year-Old Meteorite Reveals Water on Mars
Last year, noted meteorite collector Jay Piatek traveled to Morocco and bought a single stone, less than a pound in weight, that had been discovered in the country some time earlier. When he passed it on to researchers at the University of New Mexico to perform a mineral analysis, they found something unexpected.
The meteor seemed to have originated on Mars, but the rock’s composition didn’t exactly match any of the well-studied meteorites from there found previously. When the researchers compared it to data from soil and rock samples obtained by Curiosity and other recent Martian rovers, though, they realized that rather than originating in the planet’s mantle, as the others had, it appeared to have come from the Martian crust.
Most intriguingly, when they analyzed the basaltic breccia rock even more closely, they discovered it contained a large quantity of water molecules locked in its crystalline structure. While previous studies of Martian meteorites have suggested the presence of water on the red planet, this sample’s analysis, published today in Science, revealed that it contained 10 times more water than any Martian meteorite examined before.
The discovery of the water molecules in the rock at concentrations of 6000 parts per million could indicate the presence of liquid water sometime during Mars’ history. “The high water content could mean there was an interaction of the rocks with surface water either from volcanic magma, or from fluids from impacting comets during that time,” study co-author Andrew Steele of the Carnegie Institute said in a statement.
Apart from the presence of water, the researchers say that information they’ve gleaned over the course of a year-long analysis of the meteor—the first ever linked to the Martian crust—could significantly impact our understanding of the planet’s geology as a whole. The meteorite is primarily composed of chunks of basalt cemented together, indicating that it formed from rapidly cooling lava, likely on the planet’s crust. While we’ve found meteorites from the Moon that match this composition, we haven’t seen anything like it from Mars previously.
Already, the researchers determined that the specimen is roughly 2.1 billion years-old, formed during Mars’ Amazonian epoch, a time period from which we had no previous rock samples. “It is the richest Martian meteorite geochemically,” Steele said. “Further analyses are bound to unleash more surprises.”
[385]
【time two】
Do Humans Have a Biological Stopwatch?
When we witness the passage of time, according to noted physicist Paul Davies, we are actually observing how the “later states of the world differ from earlier states that we still remember.” In that sense time is like a movie: We are seeing slightly altered images playing in rapid succession.
That might explain why we perceive time as moving forward, but it fails to account for why we often perceive time moving at varying speeds. Why does it speed up when we’re having fun, but slow down when we’re bored? Most of us are fairly good at measuring short time intervals—seconds, minutes—but neuroscientists aren’t sure how we do it. “There is no one area of the brain, or system in the brain, that is solely dedicated to recording the passage of time,” says Marc Wittmann, a researcher at the Institute for Frontier Areas of Psychology and Mental Health, in Freiburg, Germany.
A leading theory is that we are endowed with the biological equivalent of a stopwatch: Somehow the brain emits a steady stream of pulses and subconsciously tallies how many were produced during a specific interval—maybe 100 pulses in your brain equals one minute. Recent research suggests that our brain runs multiple stopwatches simultaneously, depending on the kinds of tasks we’re engaged in. Unfortunately, it’s not clear what these pulses are, how they’re produced or where they’re tallied in the brain.
【234】
【time three】
Scientists believe that our biological stopwatch makes use of several brain mechanisms, including those that control memory, regulate metabolism and process sensory inputs. Perhaps because those systems are themselves not rigidly fixed but sensitive to stimuli, the number of “timing”?pulses that our brains emit per minute can increase or decrease, depending on our health, mood and even surroundings. For instance, evidence indicates that dopamine—a chemical neurotransmitter that helps regulate movement and emotion—affects our internal stopwatch. Patients who suffer from Parkinson’s disease have low dopamine levels and tend to underestimate the passage of time.
Emotional responses triggered by what we see or hear also affect our time perception. In a recent experiment, Wittmann and his colleagues had people stare at disks that appeared briefly on a computer screen. Sometimes the disks were static; other times they appeared to be coming closer or moving away. The subjects consistently overestimated the length of time that the “approaching” disks were on the screen. The reason? Wittmann speculates the oncoming disks were perceived as a potential threat—an evolutionary vestige that made us move or duck if something was approaching. So, we tense up. “Because of the threatening situation, I am totally aroused, and my internal physiological processes speed up,” says Wittmann. “And so relative to that, the outside world slows down.”
And what about that adage about time flying when we’re having fun? Wittmann says the answer has to do with attention. When we are focused on something we enjoy, our brain doesn’t keep track of the pulses emitted by our mental stopwatch. “You watch a thrilling movie, and 90 minutes pass like nothing,” says Wittmann, “but you’re waiting for the dentist for 90 minutes, and it just totally drags.”
【288】
【time four】
The Cave Art Debate
The discovery of a 40,000-year old figurine reignites debate among archaeologists about the origins—and true purpose—of art
The oldest sculpture of a human being is so small it could be hidden in your fist. Carved out of mammoth ivory, the 40,000-year-old figurine clearly represents a woman, with ballooning breasts and elaborately carved genitalia. The head, arms and legs are merely suggested. “You couldn’t get more female than this,” says Nicholas Conard, the Ohio-born archaeologist whose University of Tübingen team found the sculpture at the bottom of a vaulted cave in southwestern Germany in the fall of 2008. “Head and legs don’t matter. This is about sex, reproduction.”
The discovery of the “Venus of Hohle Fels”—named by Conard for the cave where it was found—made news around the world. Headlines called the busty statuette “prehistoric porn.” But the Venus renews a serious scholarly debate that has flared now and then since Stone Age figurines—including a waterfowl, lions and mammoths—were first discovered early last century at Hohle Fels and nearby caves. Were these literal representations of the surrounding world? Or artworks created to express emotions or abstract ideas?
Some experts viewed such pieces as “hunting magic”—representations of sought-after game animals and, therefore, survival tools, not works of art. The problem is, many of the figurines discovered so far—predators such as lions and bears—don’t correspond to what prehistoric people ate. (Their diet consisted largely of reindeer, bison and horse meat, according to bones that archaeologists have found.) Others perceive some prehistoric figurines—including a half-lion, half-man —not as imaginative works but literal depictions of hallucinations experienced by tribal shamans.
The Venus has prompted new thinking, encouraging some scholars to focus on what the figure tells us about prehistoric perceptions of beauty and obesity. Anthropologists at Victoria University of Wellington, New Zealand, recently published a study arguing that corpulent figurines symbolized the hope for a well-nourished community.
For his part, Conard emphasizes the significance of the figurine’s exaggerated anatomical features. “This is an extremely powerful depiction of the essence of being female,” Conard tells Smithsonian. He’s convinced the artifacts from these caves—regardless of whether they are art or talismans—mark a milestone in human development, an intense flowering of creativity that began in the region more than 35,000 years ago. Within a few thousand years, he says, this impulse spread to Stone Age France and Spain—where it turns up in paintings of bison, rhinos and lions on the walls of caves like Chauvet and Altamira.
University of Illinois archaeologist Olga Soffer doubts that we’ll ever know the true nature of these creations, and cautions against speculating about prehistoric imagery in terms of “18th-century Western European art.” But, art or not, Conard emphasizes that Stone Age sculptors imbued their work with larger meaning.“They’re talking about something other than their daily lives.”
【485】
【time five】
Does Deep Space Travel Cause Alzheimer’s?
NASA has big plans for manned travel in deep space. Although missions haven’t been officially announced yet, experts speculate that the agency plans to establish a space station on the far side of the moon sometime in the next decade, a stepping stone towards landing on an asteroid in 2025 and potentially trying to reach Mars sometime around 2033.
Getting to Mars, though, would require astronauts to endure a round-trip (or possibly one-way) journey that could be as long as three years—which could be particularly worrisome given the results of a study on the health effects of cosmic radiation published today in PLOS ONE. Although we’ve known for some time that the radiation experienced by space travelers could pose problems over the long term, this new study is the first to establish a link with an increased chance of Alzheimer’s disease and dementia.
The researchers, a group from NASA and the University of Rochester, came to the finding by testing a specific type of cosmic radiation—high-mass, high-charged (HZE) iron particles—on mice. This kind of radiation is of particular concern, because its high speed (a result of the force of the exploding stars it’s originally expelled from, light-years away) and large mass mean that it’s tricky to protect against.
Here on Earth, we’re largely protected from it and other types of radiation by our planet’s atmosphere and magnetic field, but even a short time in deep space means much higher levels of exposure, and we haven’t yet figured out how to construct a shield that effectively blocks it. ”Because iron particles pack a bigger wallop it is extremely difficult from an engineering perspective to effectively shield against them,” M. Kerry O’Banion, the paper’s senior author, said in a statement. “One would have to essentially wrap a spacecraft in a six-foot block of lead or concrete.”
After producing radioactive particles that generate this type of radiation using a particle accelerator at the Brookhaven National Laboratory on Long Island, the researchers exposed the mice to varying doses of the radiation, including levels comprable to what astronauts would experience on a mission to Mars. The breed of mice they used has been the subject of numerous studies on dementia and Alzheimer’s, so scientists have a relatively good understanding of how rapidly the disease and related symptoms develop over time.
But when the researchers put the mice through a series of behavioral tests—seeing if they were capable of remembering objects or specific locations—those that had been exposed to greater levels of radiation were far more likely to fail, demonstrating signs of neurological impairment far more early in life than is typical in the breed. Additionally, autopsies of these mice revealed that their brains contained higher levels of beta amyloid, the “plaque” considered a hallmark of Alzheimer’s disease.
【467】
【剩下部分不计时哦~】
This result doesn’t mean we have to abandon dreams of deep space travel—or even that this kind of radiation definitively leads to accelerated neurological degeneration—but it does show that cosmic radiation is going to be a graver concern the longer space missions get. Ingenious engineering has addressed many of the difficulties of space flight, but this remains a problem to be solved.
“These findings clearly suggest that exposure to radiation in space has the potential to accelerate the development of Alzheimer’s disease,” O’Banion said. “This is yet another factor that NASA, which is clearly concerned about the health risks to its astronauts, will need to take into account as it plans future missions.”
【116】
【越障】
Bonobos Offer Banana Bribes for Friendship
In 1719, Daniel Defoe wrote in Robinson Crusoe, ”He declar’d he had reserv’d nothing from the Men, and went Share and Share alike with them in every Bit they eat.” Defoe’s famous sharing phrase has persisted throughout the years, passing from parent to child as a lesson on the virtues of sharing with family, peers and even strangers.
But in the context of evolution and survival of the fittest, sharing makes no sense. Until now, scientists assumed that humans alone subscribed to this behavior, especially when it comes to sharing with strangers, and wrote the trait off as a quirk stemming from our unique cognitive and social development.
Sure, primatologists know that great apes help and voluntarily share food with other group mates (acts that indirectly benefits themselves). But strangers? Such a behavior is unheard of amidst species that often compete aggressively with other groups and even murder foreign individuals.
Researchers from Duke University decided to challenge the great ape’s bad sharing rep, seeking to discover whether or not our furry relatives may also have a propensity for partitioning goods with animals they do not know. The scientists chose bonobos–a type of great ape sometimes referred to as a pygmy chimpanzee–for their study. Compared to chimpanzees, bonobos possess a relatively high tolerance for strangers, so they seemed like a logical candidate for investigations into the nature of sharing.
At a bonobo sanctuary in the Democratic Republic of the Congo, they enrolled 15 wild-born bonobos orphaned and rescued from the illegal wildlife trade in four experiments. In the first experiment, the researchers led a bonobo into a room piled high with delicious banana slices. Behind two sliding doors, they placed either a friend of the main bonobo or a stranger (a bonobo unrelated and unknown to their main research subject). The bonobo with the bananas could chose to eat the food all on its own, or open the sliding door and invite both or either the friend or stranger to join in. In the second experiment, they placed only one bonobo–either the friend or stranger–behind a door and left the second room empty.
The results, which they describe this week in the journal PLoS One, confounded the researchers. In more than 70 percent of the trials, the bonobos shared their food at least once. They preferred to release the stranger over their group mate, and the stranger in turn often released the other bonobo, even though that meant splitting the food three ways and being outnumbered by two bonobos that already knew each other. They ignored the door leading to the empty room, showing that the novelty of opening the door was not motivating their behavior.
So, were the bonobos willing to share their food with strangers because of an overwhelming desire to interact with the unknown apes, or were they motivated by a sense of altruism? The researchers set up two more experiments to find out. They arranged a rope which, when pulled, released either a bonobo stranger or friend into a room which held more bananas. A mesh divider separated the main bonobo from that room, however, meaning it could neither reach the food or interact directly with the released ape. Even when there was no immediate social or culinary reward on offer, the researchers found, 9 out of 10 bonobos still chose to release their friend or the stranger at least once, allowing the other ape to reach the banana reward.
Bonobos drew the line, however, in the final experiment. This setup allowed both bonobos to access the food, but did not let them interact physically with the stranger or friend. In other words, the main bonobo would have to forfeit some of its food but receive no reward of sniffing, petting or playing with another ape. None of the bonobos chose to open the door, suggesting that the seemingly altruistic sharing of the first two experiments was just a ploy to gain gratifying access to intriguing strangers and, to a lesser extent, friends. The third experiment, however, shows that the bonobos’ motivations are not completely selfish. When the food was so far out of reach that they themselves could not benefit, they allowed a friend or stranger to enjoy it instead.
Bonobos, in other words, break the rules when it comes to sharing, showing that kindness towards strangers is not unique to humans. Oddly enough, unlike their bipedal counterparts, bonobos even seem to prefer strangers to group mates. This behavior, the study authors think, might have evolved to help groups of bonobos expand their social networks. Further investigations may lend clues about evolution of sharing in humans.
“Like chimpanzees, our species would kill strangers; like bonobos, we could also be very nice to strangers,” said Jingzhi Tan, an evolutionary anthropologist at Duke University and lead author of the paper, in a statement. “Our results highlight the importance of studying bonobos to fully understand the origins of such human behaviors.”
【827】
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发表于 2013-1-7 01:16:54
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