每天四篇Discovery News

bonfin

RT

bonfin

1-1 Should We Turn Off the Lights?

Street lighting is changing bug communities and that is affecting everything from the songs birds sing to the makeup of people.

A new study found that scavenger and predator insects both collect near the lights. It also shows for the first time that their composition is affected by the lighting. The study is published in the latest Biology Letters.

In fact, streetlights and other forms of artificial lighting may affect all ecosystem members, from bugs to humans.

“The range of effects of light pollution are really very diverse,” lead author Thomas Davies told Discovery News. “They can affect reproductive successes in sea turtles, the timings of bird songs and even the physiology of humans.”

He and his colleagues believe that “we are facing an insect biodiversity crisis,” which merits our attention because “insects provide crucial services to humans, such as pollination and decomposition to organic matter.”

Davies is a postdoctoral research fellow at the University of Exeter’s Environment and Sustainability Institute. He and colleagues Jonathan Bennie and Kevin Gaston deployed several insect traps on grassy vegetation under and between streetlights in Helston, Cornwall, UK.

The traps were left in place for three days and nights and analyzed 30 minutes prior to sunrise and sunset.The amount of vegetation in an area was taken into account.

A total of 1194 ground-dwelling invertebrates representing 60 different species were collected during the study. Individuals were far more abundant within close proximity to street lighting, no matter the time of day. Harvestmen, ants, ground beetles, woodlice, and amphipods (small crustaceans that include fleas) were most prevalent.

“These species are generally more mobile than others, making it more likely that they will encounter habitats that are lit to varying levels of brightness, providing them with the opportunity to make a selection of a preferred habitat,” Davies explained.

“Why these species are found more in brightly lit areas is not clear,” he continued. “Research on this subject is beginning to highlight that larger species with more sensitive eyes are more susceptible to street lighting, and in the case of this study, the largest bodied mobile invertebrates were predators and scavengers, such as ground beetles and harvestmen.”

People with homes closer to street lights may be at greater risk for exposure to certain insects, and even the diseases some of them could harbor. For example, another recent study showed that Triatoma dimidiate, an insect that can carry Chagas disease (an inflammatory, infectious illness), infested houses that were in closer proximity to street lighting, Davies said.

The problems associated with lighting are predicted to continue, given that recent estimates suggest that artificial lighting is increasing globally at a rate of 6 percent per year.

“We should be concerned about any activity which affects invertebrate communities, but we should also be concerned about the affects of street lighting on other communities as well,” Davies said, adding that switching lights off during periods of low usage, dimming lights, and reducing overall artificial light in environments are all possible solutions.

John Hopkins, principal adviser for Natural England, agrees with the study’s conclusions and sees it “as a significant piece of research relevant to a developing aspect of public policy.” Hopkins explained that the recently published “National Planning Policy Framework for England” requires that local authorities take account the impact of artificial lighting on biodiversity when making planning decisions.

“So far, much of the research has shown that artificial light changes the behavior of individual species,” Hopkins told Discovery News. “These effects are very diverse and range, for example, from changes to mate locating success, migration and predation behaviors, among others.”

He added, “The difficulty is currently in understanding what these varied changes between species mean to the way ecosystems work. The (latest) findings are one of the first indications that there may be very profound effects of artificial light on ecosystem processes…Although invertebrates seem to be lowly life forms, in many ecosystems they have more impact than birds and mammals.”

1-2 Ancient Egyptians Tracked Eclipsing Binary Star Algol

Turn your telescope to the constellation of Perseus and you might note an unusual star called Algol, dubbed the "Demon Star" or the "Raging One." You wouldn't notice anything much different at first, unless you happened to be looking during a window of a few hours -- every 2.867 days -- when Algol's brightness visibly dims.

This unusual feature was first noticed back in 1667 by an astronomer named Geminiano Montanari, and later confirmed -- with a proposed possible mechanism -- in 1783 by John Goodricke, who precisely measured the period of variability: it dims every 2.867 days.

But a new paper by researchers at the University of Helsinki, Finland, claims that the ancient Egyptians may have recorded Algol's periodic variability 3000 years ago, based on their statistical analysis of a bit of papyrus known as the Cairo Calendar.

This isn't the first time people have hypothesized that Algol's variable nature was known prior to its discovery in the 17th century. Certainly it was a familiar object, prominent in mythology and lore. In the second century, Ptolemy referred to Algol as the "Gorgon of Perseus," and associated it with death by decapitation. (In Greek mythology, the hero Perseus slays the snake-headed Gorgon, Medusa, by chopping off her head.)

Other cultures also associated the star with violence and bad fortune. It's no coincidence that H.P. Lovecraft marked the onset of his final battle in the 1919 short story, "Beyond the Wall of Sleep," with the appearance of a nova near Algol.

But the Helsinki researchers go beyond mythology and conjecture and provide a solid statistical analysis, based on historical documentation.

Goodricke proposed that Algol's periodic variability was due to an eclipsing factor: namely, an orbiting dark body occasionally passed in front of the star, dimming its brightness temporarily.

Alternatively, he suggested that Algol itself had a darker side that turned toward the Earth every 2.687 days.

His hypothesis wouldn't be confirmed until 1881, when Edward Charles Pickering discovered that Algol is actually a binary star system: there were two stars circling together, Algol A and Algol B.

Even more intriguing: it was an "eclipsing binary," i.e., one in which the dimmer star in the system occasionally passes in front of its brighter sibling, dimming the latter according to predictable periods. Goodricke's hypothesis was correct.

Actually, astronomers now know that Algol is a triple-star system, with a third star, Algol C, located a bit further out from the main pair, with a larger orbit.

All of this is necessary background for understanding the conclusions of the Helsinki scientists. The whole point of tracking the heavens so meticulously, for the Egyptians, was to make predictions about the future, dividing the calendar into "lucky" and "unlucky" days. The Cairo Calendar, while badly damaged, nonetheless contains a complete list of such days over a full year, circa 1200 B.C.

How did the Egyptians decide how to rate specific days? That's a mystery. But the Finnish team took the raw data and reassembled it into a tie series, then used statistical techniques to determine the cycles within it. There were two significant periodic cycles. One was 29.6 days, very close to current estimates of a lunar month (29.53059 days).

The second periodic cycle was 2.85 days. Lead author Lauri Jetsu and her colleagues argue that this corresponds to Argol's variable period. It's suspiciously close to the 2.867 period Goodricke measured back in 1783.

Close, yes, but it's not a precise match, which is problematic. The Egyptians weren't known to be sloppy in their astronomical calculations. They should have been able to pinpoint a value much closer to Goodricke's -- unless, say, Algol's period changes over time.

There is some evidence that this might be the case, possibly due to the presence of the third star in the Algol system. Calculating the behavior of a two-body system is one thing; grappling with the dreaded "three-body problem" is quite another, particularly since astronomers are only working with roughly 300 years of data. Algol looks like it's living up to its "Demon Star" moniker.

That's where Jetsu et al's paper might prove to be more than just an intriguing historical oddity. It provides some missing data from 3000 years ago, which could help astronomers further constrain their models for Algol's variable behavior.

1-3 Bronze-Age 'Facebook' Stone Conveyed 'Likes'

A Bronze Age version of Facebook has emerged from granite rocks in Russia and northern Sweden, revealing a thousands-of-years-old timeline filled with an archaic version of the Facebook "like."

Using computer modeling, Mark Sapwell, a Ph.D. archaeology student at Cambridge University, analyzed some 3,500 rock art images from Nämforsen in Northern Sweden and Zalavruga in Western Russia.

"Although this rock art has been documented from the early 1900s, the modeling has allowed a unique look at the interesting way these images have been arranged and accumulated over time," Sapwell told Discovery News.

Carved from about 4000 B.C. up to the Bronze Age, the rock art shows animals, people, boats, hunting scenes -- even very early centaurs and mermaids. It was produced by generations of semi nomadic people, who lived more inland in winter to hunt elk, and then occupied areas closer to coasts and rivers to fish.

As they were located in important and prominent locations on river crossroads, the rock art landscapes were likely very visible points where passing travellers would take notice of the traces of people who came before them, adding their own mark on the world.

"The rock art we see today is the result of a culmination of many repeated acts of carving, each responding to each other over time. Like a Facebook status invites comment, the rock art appears very social and invites addition," Sapwell said.

Usually clustered on the granite rocks, the images ranged from groups of one to two images to rock art panels with over 500 images. Larger clusters represented a greater response and conversation between people.

"Additions to these works were exacting replications, stamps of approval -- a primitive 'like,'" Sapwell said.

Images involved in those clusters were the most popular or most discussed for that time. For example, in earlier periods (around 4000-3500 B.C.), a silhouette style of elk image is almost always seen among large clusters and rarely alone.

"One exciting part of the study is that the preference towards these popular images change through time. A very big change at Namforsen is the shift from elk to boat images, as if the 'topic to talk about' shifted from land to water," Sapwell said.

The shift is dated to around 2000-1800 B.C., a time when travel and long-distance exchange between communities was becoming more important.

Another interesting part of the find is the importance of unique forms of hybrid imagery (for example a half-man half elk, or half-man half-boat), which was tried out in the early periods, but became less popular from around 3500 B.C.

"So generally, what we see in these landscapes are very interesting cases where through prehistory, particular themes in everyday life become worth commenting on. A little like the fashions of Facebook comments, these topics are seen to fall in and out of favor," Sapwell said.

According to Sapwell, the enormous natural canvases attracted so much interest because their social network power was well understood by early Bronze Age people.

"Like today, people have always wanted to feel connected to each other -- this was an expression of identity for these very early societies, before written language," Sapwell said.

1-4 Are Sweets Making You Stupid?

What you eat may affect how you learn, say UCLA researchers in a new study on the effects of fructose and omega-3 fatty acids on the behavior of rats.

Rats that were fed only fructose and standard rat chow had more trouble navigating a maze at the end of six weeks than rats who were fed a diet supplemented with omega-3 fatty acids, according to results published in the Journal of Physiology.

"Our findings illustrate that what you eat affects how you think," said Fernando Gomez-Pinilla, a professor of neurosurgery and integrative biology and physiology. "Eating a high-fructose diet over the long term alters your brain's ability to learn and remember information. But adding omega-3 fatty acids to your meals can help minimize the damage."

The animals trained on a maze with visual landmarks twice daily for five days before starting the experimental diet. Six weeks later, the researchers tested the rats' ability to recall the route and escape the maze.

"The second group of rats navigated the maze much faster than the rats that did not receive omega-3 fatty acids," Gomez-Pinilla said. "The DHA-deprived animals were slower, and their brains showed a decline in synaptic activity. Their brain cells had trouble signaling each other, disrupting the rats' ability to think clearly and recall the route they'd learned six weeks earlier."

The faster rats received omega-3 fatty acids in the form of flaxseed oil and docosahexaenoic acid (DHA), which protects against damage to the brain's synapses, or chemical connections. The DHA-deprived rats also developed signs of resistance to insulin.

"Our findings suggest that consuming DHA regularly protects the brain against fructose's harmful effects," said Gomez-Pinilla. "It's like saving money in the bank. You want to build a reserve for your brain to tap when it requires extra fuel to fight off future diseases."

Still, no matter how much salmon we eat, we should also avoid sweets most of the time -- and not just high-fructose corn syrup, Gomez-Pinilla told the Los Angeles Times. High-fructose corn syrup has taken most of the bad rap lately, because it's added to so many foods, but that doesn't give regular white sugar a pass.