星空女人频道: 2013-07-21

2013年7月27日星期六

Evolution on the inside track: How viruses in gut bacteria change over time

July 26, 2013 — Humans are far more than merely the sum total of all the cells that form the organs and tissues. The digestive tract is also home to a vast colony of bacteria of all varieties, as well as the myriad viruses that prey upon them. Because the types of bacteria carried inside the body vary from person to person, so does this viral population, known as the virome.

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By closely following and analyzing the virome of one individual over two-and-a-half years, researchers from the Perelman School of Medicine at the University of Pennsylvania, led by professor of Microbiology Frederic D. Bushman, Ph.D., have uncovered some important new insights on how a viral population can change and evolve -- and why the virome of one person can vary so greatly from that of another. The evolution and variety of the virome can affect susceptibility and resistance to disease among individuals, along with variable effectiveness of drugs.

Their work was published in the Proceedings of the National Academy of Sciences.

Most of the virome consists of bacteriophages, viruses that infect bacteria rather than directly attacking their human hosts. However, the changes that bacteriophages wreak upon bacteria can also ultimately affect humans.

"Bacterial viruses are predators on bacteria, so they mold their populations," says Bushman. "Bacterial viruses also transport genes for toxins, virulence factors that modify the phenotype of their bacterial host." In this way, an innocent, benign bacterium living inside the body can be transformed by an invading virus into a dangerous threat.

At 16 time points over 884 days, Bushman and his team collected stool samples from a healthy male subject and extracted viral particles using several methods. They then isolated and analyzed DNA contigs (contiguous sequences) using ultra-deep genome sequencing .

"We assembled raw sequence data to yield complete and partial genomes and analyzed how they changed over two and a half years," Bushman explains. The result was the longest, most extensive picture of the workings of the human virome yet obtained.

The researchers found that while approximately 80 percent of the viral types identified remained mostly unchanged over the course of the study, certain viral species changed so substantially over time that, as Bushman notes, "You could say we observed speciation events."

This was particularly true in the Microviridae group, which are bacteriophages with single-stranded circular DNA genomes. Several genetic mechanisms drove the changes, including substitution of base chemicals; diversity-generating retroelements, in which reverse transcriptase enzymes introduce mutations into the genome; and CRISPRs (Clustered Regularly Interspaced Short Palindromic Repeats), in which pieces of the DNA sequences of bacteriophages are incorporated as spacers in the genomes of bacteria.

Such rapid evolution of the virome was perhaps the most surprising finding for the research team. Bushman notes that "different people have quite different bacteria in their guts, so the viral predators on those bacteria are also different. However, another reason people are so different from each other in terms of their virome, emphasized in this paper, is that some of the viruses, once inside a person, are changing really fast. So some of the viral community diversifies and becomes unique within each individual."

Since humans acquire the bacterial population -- and its accompanying virome -- after birth from food and other environmental factors, it's logical that the microbial population living within each of us would differ from person to person. But this work, say the researchers, demonstrates that another major explanatory factor is the constant evolution of the virome within the body. That fact has important implications for the ways in which susceptibility and resistance to disease can differ among individuals, as well as the effectiveness of various drugs and other treatments.

The research was supported by Human Microbiome Roadmap Demonstration Project (UH2DK083981) the Penn Genome Frontiers Institute, and the University of Pennsylvania Center for AIDS Research (CFAR; P30 Al 045008).

Samuel Minot, Alexandra Bryson, Christel Chehoud, Gary D. Wu, James D. Lewis, all from Penn, are co-authors.

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Gadget genius: Nanotechnology breakthrough is big deal for electronics

July 26, 2013 — University of Akron researchers have developed new materials that function on a nanoscale, which could lead to the creation of lighter laptops, slimmer televisions and crisper smartphone visual displays.

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Known as "giant surfactants" -- or surface films and liquid solutions -- the researchers, led by Stephen Z.D. Cheng, dean of UA's College of Polymer Science and Polymer Engineering, used a technique known as nanopatterning to combine functioning molecular nanoparticles with polymers to build these novel materials.

The giant surfactants developed at UA are large, similar to macromolecules, yet they function like molecular surfactants on a nanoscale, Cheng says. The outcome? Nanostructures that guide the size of electronic products.

More efficient designs possible

Nanopatterning, or self-assembling molecular materials, is the genius behind the small, light and fast world of modern-day gadgetry, and now it has advanced one giant step thanks to the UA researchers who say these new materials, when integrated into electronics, will enable the development of ultra-lightweight, compact and efficient devices because of their unique structures.

During their self-assembly, molecules form an organized lithographic pattern on semiconductor crystals, for use as integrated circuits. Cheng explains that these self-assembling materials differ from common block copolymers (a portion of a macromolecule, comprising manyunits, that has at least one feature which is not present in the adjacent portions) because they organize themselves in a controllable manner at the molecular level.

"The IT industry wants microchips that are as small as possible so that they can manufacture smaller and faster devices," says Cheng, who also serves as the R.C. Musson and Trustees Professor of Polymer Science at UA.

He points out that the current technique can produce the spacing of 22 nanometers only, and cannot go down to the 10 nanometers or less necessary to create tiny, yet mighty, devices. The giant surfactants, however, can dictate smaller-scale electronic components.

"This is exactly what we are pursuing -- self-assembling materials that organize at smaller sizes, say, less than 20 or even 10 nanometers," says Cheng, equating 20 nanometers to 1 /4,000th the diameter of a human hair.

Team's work has commercial applications

An international team of experts, including George Newkome, UA vice president for research, dean of the Graduate School, and professor of polymer science at UA; Er-Qiang Chen of Peking University in China; Rong-Ming Ho of National Tsinghua University in Taiwan; An-Chang Shi of McMaster University in Canada; and several doctoral and postdoctoral researchers from Cheng's group, have shown how well-ordered nanostructures in various states, such as in thin films and in solution, offer extensive applications in nanotechnology.

The team's study is highlighted in a pending patent application through the University of Akron Research Foundation and in a recent journal article, "Giant surfactants provide a versatile platform for sub-10-nm nanostructure engineering" published in Proceedings of the National Academy of Sciences of the United States of America (110, 10078-10083, 2013).

"These results are not only of pure scientific interest to the narrow group of scientists, but also important to a broad range of industry people," says Cheng, noting that his team is testing real-world applications in nanopatterning technologies and hope to see commercialization in the future.

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Technology/equipment issues account for almost one in four operating room errors

Inability to use the technology/equipment, lack of availability, and faulty devices/machines made up the bulk of the problems, the analysis indicates.

The researchers methodically searched for published studies on errors and problems arising in operating rooms in electronic databases. After applying a quality assessment technique, they found 28 studies out of a total of 19,362 pieces of research that were suitable for inclusion in the analysis.

Technology/equipment issues cropped up in an average of 15.5% of malpractice claims. Across all the studies, an average of 2.4 errors was recorded for each procedure, although this figure rose to 15.5 when an independent observer recorded the errors. Equipment and/or technology issues accounted for almost a quarter (23.5%) of these errors.

Eight studies categorised the different types of equipment error: the configuration or settings caused problems in more than four out of 10 cases (43.4%); availability of the required device/machine was an issue in just over 37% of cases; while in almost a third of cases, the equipment or technology wasn't working properly.

Four studies looked at the severity of mistakes in the operating room, classifying a fifth as "major," of which equipment failures accounted for a fifth, compared with 8% and 13%, respectively, for communication and technical failures.

While the type and rate of equipment failures varied widely, depending on the study and surgical procedure involved, surgery that relied heavily on technology had higher rates of problems.

Three studies reported on the deployment of an equipment/technology checklist before surgery and showed that this could halve the error rate, prompting the authors to recommend that a generic equipment check should become routine practice, and be included in the current World Health Organization Surgical Safety Checklist.

The authors appreciate that technological advances have improved the chances of survival and quality of life of people undergoing surgery. But they caution: "The increasing use of technology in all surgical specialties may also increase the complexity of the surgical process, and may represent an increasing propensity to error from equipment failure."

Previous evidence suggests that medical errors affect up to 16% of all patients admitted to hospital, around half of which are attributable to surgical procedures, they add.

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Glass scaffolds help heal bone, show promise as weight-bearing implants

This marks the first time researchers have shown a glass implant strong enough to bear weight can also integrate with bone and promote bone growth, says lead researcher Dr. Mohamed N. Rahaman, professor of materials science and engineering at Missouri S&T.

In previous work, the Missouri S&T researchers developed a glass implant strong enough to handle the weight and pressure of repetitive movement, such as walking or lifting. In their most recent study, published in the journal Acta Biomaterialia, the research team reported that the glass implant, in the form of a porous scaffolding, also integrates with bone and promotes bone growth.

This combination of strength and bone growth opens new possibilities for bone repair, says Rahaman, who also directs Missouri S&T's Center for Biomedical Science and Engineering, where the research was conducted.

"Right now, there is no synthetic material that is practical for structural bone repair," Rahaman says.

Conventional approaches to structural bone repair involve either the use of a porous metal, which does not reliably heal bone, or a bone allograft from a cadaver. Both approaches are costly and carry risks, Rahaman says. He thinks the type of glass implant developed in his center could provide a more feasible approach for repairing injured bones. The glass is bioactive, which means that it reacts when implanted in living tissue and convert to a bone-like material.

In their latest research, Rahaman and his colleagues implanted bioactive glass scaffolds into sections of the calvarial bones (skullcaps) of laboratory rats, then examined how well the glass integrated with the surrounding bone and how quickly new bone grew into the scaffold. The scaffolds are manufactured in Rahaman's lab through a process known as robocasting -- a computer-controlled technique to manufacture materials from ceramic slurries, layer by layer -- to ensure uniform structure for the porous material.

In previous studies by the Missouri S&T researchers, porous scaffolds of the silicate glass, known as 13-93, were found to have the same strength properties as cortical bone. Cortical bones are those outer bones of the body that bear the most weight and undergo the most repetitive stress. They include the long bones of the arms and legs.

But what Rahaman and his colleagues didn't know was how well the silicate 13-93 bioactive glass scaffolds would integrate with bone or how quickly bone would grow into the scaffolding.

"You can have the strongest material in the world, but it also must encourage bone growth in a reasonable amount of time," says Rahaman. He considers three to six months to be a reasonable time frame for completely regenerating an injured bone into one strong enough to bear weight.

In their studies, the S&T researchers found that the bioactive glass scaffolds bonded quickly to bone and promoted a significant amount of new bone growth within six weeks.

While the skullcap is not a load-bearing bone, it is primarily a cortical bone. The purpose of this research was to demonstrate how well this type of glass scaffolding -- already shown to be strong -- would interact with cortical bone.

Rahaman and his fellow researchers in the Center for Biomedical Science and Engineering are now experimenting with true load-bearing bones. They are now testing the silicate 13-93 implants in the femurs (leg bones) of laboratory rats.

In the future, Rahaman plans to experiment with modified glass scaffolds to see how well they enhance certain attributes within bone. For instance, doping the glass with copper should promote the growth of blood vessels or capillaries within the new bone, while doping the glass with silver will give it antibacterial properties.

Working with Rahaman are Xin Liu, a Ph.D. student in materials science and engineering at Missouri S&T; Dr. Yongxing Liu, an assistant research professor of materials science and engineering; Dr. B. Sonny Bal, associate professor of orthopaedic surgery at the University of Missouri-Columbia; and Dr. Lynda Bonewald, Curators' Professor director of the bone biology research program at the University of Missouri-Kansas City School of Dentistry.

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2013年7月26日星期五

Video: WaterColorBot paints its way to existence Robot Gadget Master

2013/07/26

WaterColorBot Robots, eh? They may one day enslave us humans with their tireless and indefatigable strength and logic (hurling cinder blocks at us when angry), but they will never capture the essence of our existence and create art. Will they?

Enter the “Water colour Robot”. They are not the colour of water, they paint water colours! Actually, it’s a rather neat educational robotic kit that paints pleasing vector-based images.

Some self-assembly is required but major components – such as the chassis, carriage, and motor controller board – come pre-assembled, reports GeekyGadgets.com. Based on two motors, it uses the same X-Y-co-ordinate controlling mechanism as Etch-a-Sketch. You can use with a Mac, Windows, or Linux (Ubuntu) computer, and it can also follow along as you sketch in real time.

You can import artwork in the SVG file format and the team say you can use Inkscape to convert file formats – such as PDF and Illustrator – into SVG.

If you really like the gadget, you can buy the company. At least, you can contribute to its funding on KickStarter. The project has already raised $68,422 busting it’s $50,000 goal with 19 days to go, at time of writing.

The team writes:

The WaterColorBot works with standard watercolor paints and paper, so that you never need to purchase specialized or expensive supplies. It is made in the USA with a tough and sturdy wooden frame to last for years of use.
While a robotic painting “printer” can be an incredibly fun thing on its own, the WaterColorBot is also a genuine (if simple and friendly) computer-automated, numerically controlled (CNC) machine– and that lets you do some amazing things.

Specifically, you get:

The WaterColorBot Chassis (already built)
The lower deck (“spoilboard”) of the WaterColorBot
The WaterColorBot Carriage (already built) with integrated brush holder, brush-lift servo motor, and cable guide
Two precision stepper motors
The EiBotBoard 2.0 USB motor controller (readymade)
USB Cable
Universal input plug-in power supply (with US-style plug)
A set of Crayola water colours with brush
Five sheets of 9×12″ watercolor paper
Three polypropylene water dishes
Winches, cord, and the X and Y guide rods
Hex wrench and fasteners
A quick start guide

WaterColorBot 2

Once it ships, say the people behind it, the WaterColorBot will be a fully open-source project (hardware, firmware, and software) to be extended and repurposed as the world sees fit. Good for them!

Will there be an API published for making new WaterColorBot Apps? Yes, they write in the project’s FAQ:

Our RoboPaint software includes a RESTful API that can be used to interface with the WaterColorBot. For example, we are currently working towards an iPad app that can control the WaterColorBot in real time, in collaboration with Erin “RobotGrrl” Kennedy ( http://robotgrrl.com ). You can also start with any of our example apps (based in Python, Java/Processing, or Javascript), or directly from the EiBotBoard documentation, using any software that can communicate with a USB serial port.

See Super Awesome Sylvia’s WaterColorBot »

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Global warming to cut snow water storage 56 percent in Oregon watershed

July 26, 2013 — A new report projects that by the middle of this century there will be an average 56 percent drop in the amount of water stored in peak snowpack in the McKenzie River watershed of the Oregon Cascade Range -- and that similar impacts may be found on low-elevation maritime snow packs around the world.

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The findings by scientists at Oregon State University, which are based on a projected 3.6 degree Fahrenheit temperature increase, highlight the special risks facing many low-elevation, mountainous regions where snow often falls near the freezing point. In such areas, changing from snow to rain only requires a very modest rise in temperature.

As in Oregon, which depends on Cascade Range winter snowpack for much of the water in the populous Willamette Valley, there may be significant impacts on ecosystems, agriculture, hydropower, industry, municipalities and recreation, especially in summer when water demands peak.

The latest study was one of the most precise of its type done on an entire watershed, and was just published in Hydrology and Earth System Sciences, with support from the National Science Foundation. It makes it clear that new choices are coming for western Oregon and other regions like it.

"In Oregon we have a water-rich environment, but even here we will have to manage our water resources differently in the future," said Eric Sproles, who led this study as a doctoral student at OSU.

"In the Willamette River, for instance, between 60-80 percent of summer stream flow comes from seasonal snow above 4,000 feet," he said. "As more precipitation falls as rain, there will more chance of winter flooding as well as summer drought in the same season. More than 70 percent of Oregon's population lives in the Willamette Valley, with the economy and ecosystems depending heavily on this river."

Annual precipitation in the future may be either higher or lower, the OSU researchers said. They did calculations for precipitation changes that could range 10 percent in either direction, although change of that magnitude is not anticipated by most climate models.

The study made clear, so far as snowpack goes, that temperature is the driving force, far more than precipitation. Even the highest levels of anticipated precipitation had almost no impact on snow-water storage, they said.

"This is not an issue that will just affect Oregon," said Anne Nolin, a professor in the College of Earth, Ocean, and Atmospheric Sciences, and co-author of the study. "You may see similar impacts almost anywhere around the world that has low-elevation snow in mountains, such as in Japan, New Zealand, Northern California, the Andes Mountains, a lot of Eastern Europe and the lower-elevation Alps."

The focus of this study was the McKenzie River, a beautiful, clear mountain river that rises in the high Cascade Range near the Three Sisters volcanoes, and supplies about 25 percent of the late summer discharge of the Willamette River. Researchers said this is one of the most detailed studies of its type done on a large watershed.

Among the findings of the study:

The average date of peak snowpack in the spring on this watershed will be about 12 days earlier by the middle of this century.
The elevation zone from 1,000 to 1,500 meters will lose the greatest volume of stored water, and some locations at that elevation could lose more than 80 days of snow cover in an average year.
Changes in dam operations in the McKenzie River watershed will be needed, but will not be able to make up for the vast capability of water storage in snow.
Summer water flows will be going down even as Oregon's population surges by about 400,000 people from 2010 to 2020.
Globally, maritime snow comprises about 10 percent of Earth's seasonal snow cover.
Snowmelt is a source of water for more than one billion people.
Precipitation is highly sensitive to temperature and can fall as rain, snow, or a rain-snow mix.

The model developed for this research, scientists said, could be readily adapted to help other regions in similar situations determine their future loss of snow water in the future.

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Quantum of sonics: Bonded, not stirred

Nanoparticles are extremely useful but are difficult to contain because they are invisible and are easily carried in the air. They can also enter the body easily, creating a concern for the safety of industrial workers and the public. A new method to stick nanoparticles to one another into something you can handle safely with your fingers, without changing their useful properties, could have implications for a range of everyday applications.

"Using ultrasound is a very gentle low-energy process compared to traditional furnaces and welding, so even active drugs and enzymes can easily be built into carriers to make new hybrid materials," says Prof. Barralet, lead investigator of the study and Director of Research in the Department of Surgery at the Research Institute of the McGill University Health Centre (RI-MUHC).

Ultrasound induces short-lived bubbles (known as cavitation) that create, for a fraction of a microsecond, when they collapse, 'hotspots' of thousands of degrees. Because this bubble formation is a random and infrequent process, scientists have struggled with ways to harness this incredibly powerful phenomenon for assembling materials rather than for destroying them. The key to the McGill team's finding was developing a way to localize cavitation at the nanoparticles' surface. This led to the discovery that their phosphate coating interacts with unstable radicals created at these hotpots and makes the nanoparticles 'weld' together irreversibly.

Just as a mixologist (cocktail waiter) shakes drinks together to create your favourite martini, materials scientists can now simply mix preformed nanoparticles together and zap them in the ultrasonic bath to create new weird and wonderful hybrid and fully functional microparticle materials, such as conductive ceramic catalysts, magnetic polymers, and drug-loaded metals.

"Our discovery may help alleviate the loss of platinum from catalytic converters in car exhausts, for example. Half of the platinum mined annually worldwide is used to make catalytic converters and up to half of this platinum is lost into the atmosphere during the lifetime of the car. This results from a lack of a better method -- up to now -- for bonding nanoparticles in a robust and durable manner while still maintaining their activity."

The study's co-author and former McGill doctoral student, David Bassett, helped make the discovery when he spotted something unusual in the bottom of his ultrasonic bath.

"Instead of getting smaller, these things grew and kept on growing. We went up many blind alleys and it took me three years to unravel what was going on. It was painstaking but now it's really satisfying to finally have a grip on it."

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WaterColorBot paints its way to existence Robot Gadget Master

2013/07/26

Enter the “Water colour Robot”. They are not the colour of water, they paint water colours! Actually, it’s a rather neat educational robotic kit that paints pleasing vector-based images.

You can import artwork in the SVG file format and the team say you can use Inkscape to convert file formats – such as PDF and Illustrator – into SVG.

The team writes:

The WaterColorBot works with standard watercolor paints and paper, so that you never need to purchase specialized or expensive supplies. It is made in the USA with a tough and sturdy wooden frame to last for years of use.
While a robotic painting “printer” can be an incredibly fun thing on its own, the WaterColorBot is also a genuine (if simple and friendly) computer-automated, numerically controlled (CNC) machine– and that lets you do some amazing things.

Specifically, you get:

The WaterColorBot Chassis (already built)
The lower deck (“spoilboard”) of the WaterColorBot
The WaterColorBot Carriage (already built) with integrated brush holder, brush-lift servo motor, and cable guide
Two precision stepper motors
The EiBotBoard 2.0 USB motor controller (readymade)
USB Cable
Universal input plug-in power supply (with US-style plug)
A set of Crayola water colours with brush
Five sheets of 9×12″ watercolor paper
Three polypropylene water dishes
Winches, cord, and the X and Y guide rods
Hex wrench and fasteners
A quick start guide

WaterColorBot 2

Once it ships, say the people behind it, the WaterColorBot will be a fully open-source project (hardware, firmware, and software) to be extended and repurposed as the world sees fit. Good for them!

Will there be an API published for making new WaterColorBot Apps? Yes, they write in the project’s FAQ:

Our RoboPaint software includes a RESTful API that can be used to interface with the WaterColorBot. For example, we are currently working towards an iPad app that can control the WaterColorBot in real time, in collaboration with Erin “RobotGrrl” Kennedy ( http://robotgrrl.com ). You can also start with any of our example apps (based in Python, Java/Processing, or Javascript), or directly from the EiBotBoard documentation, using any software that can communicate with a USB serial port.

See Super Awesome Sylvia’s WaterColorBot »

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Pesticides contaminate frogs from Californian national parks

California's Central Valley is one of the most intensely farmed regions in North America, producing 8% of U.S agricultural output by value. While the use of pesticides such as triazines, endosulfan and organophosphates is common across the U.S., California uses more pesticides than any other state.

"Our results show that current-use pesticides, particularly fungicides, are accumulating in the bodies of Pacific chorus frogs in the Sierra Nevada," said Kelly Smalling a research hydrologist from the U.S. Geological Survey. "This is the first time we've detected many of these compounds, including fungicides, in these remote locations."

The Pacific chorus frog Pseudacris Regilla can be found in abundance across the state's Sierra Nevada mountain range. As with other amphibians, agrochemicals potentially pose a threat to chorus frogs, as exposure to pesticides can decrease their immune system, thereby increasing the risk of disease.

The team collected frogs, as well as water and sediment samples, from seven ponds ranging from Lassen Volcanic National Park at the northern most point of Central Valley, to the Giant Sequoia National Monument in the valley's southern extent. All sites were downwind of agricultural areas.

"The samples were tested for 98 types of pesticides, traces of which were found in frog tissues from all sites," said Smalling. "We found that even frogs living in the most remote mountain locations were contaminated by agricultural pesticides, transported long distances in dust and by rain."

Two fungicides, commonly used in agriculture, pyraclostrobin and tebuconazole, and one herbicide, simazine, were the most frequently detected compounds, and this is the first time these compounds have ever been reported in wild frog tissue. Another commonly detected pesticide was DDE (Dichlorodiphenyldichloroethylene) a breakdown product of DDT which was banned in the United States in 1972. The continued presence of a DDT byproduct reveals how long this banned chemical can impact biodiversity.

A comparison of the frog tissue with water and sediment collected from the same sites shows that the frogs were the more reliable indicator of chemical exposure. This is partly due to the physical-chemical properties of the l compounds and biological influences such as such as organism specific metabolism and life history. Documenting the occurrence of these compounds is an important first step in figuring out the health consequence associated with the exposures.

"Very few studies have considered the environmental occurrence of pesticides, particularly fungicides which can be transported beyond farmland," concluded Smalling. "Our evidence raises new challenges for resource managers; demonstrating the need to keep track of continual changes in pesticides use and to determine potential routes of exposure in the wild."

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Rocks can restore our climate ... after 300,000 years

July 26, 2013 — A study of a global warming event that happened 93 million years ago suggests that the Earth can recover from high carbon dioxide emissions faster than thought, but that this process takes around 300,000 years after emissions decline.Scientists from Oxford University studied rocks from locations including Beachy Head, near Eastbourne, and South Ferriby, North Lincolnshire, to investigate how chemical weathering of rocks 'rebalanced' the climate after vast amounts of carbon dioxide (CO₂) were emitted during more than 10,000 years of volcanic eruptions.

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In chemical weathering CO₂ from the atmosphere dissolved in rainwater reacts with rocks such as basalt or granite, dissolving them so that this atmospheric carbon then flows into the oceans, where a large proportion is 'trapped' in the bodies of marine organisms.

The team tested the idea that, as CO₂ warms the planet, the reactions involved in chemical weathering speed up, causing more CO₂ to be 'locked away', until, if CO₂ emissions decline, the climate begins to cool again. The Oxford team looked at evidence from the 'Ocean Anoxic Event 2' in the Late Cretaceous when volcanic activity spewed around 10 gigatonnes of CO₂ into the atmosphere every year for over 10,000 years. The researchers found that during this period chemical weathering increased, locking away more CO₂ as the world warmed and enabling the Earth to stabilise to a cooler climate within 300,000 years, up to four times faster than previously thought.

A report of the research is published in Nature Geoscience.

'Looking at this event is rather like imagining what the Earth would be like if humans disappeared tomorrow,' said Dr Philip Pogge von Strandmann of Oxford University's Department of Earth Sciences, who led the research. 'Volcanic CO₂ emissions in this period are similar to, if slightly slower than, current manmade emissions so that we can imagine a scenario in which, after human CO₂ emissions ceased, the planet's climate would start to recover and cool down. The bad news is that it's likely this would take around 300,000 years.'

Reconstructing a record of past chemical weathering is challenging because of how plants and animals take carbon out of the environment. To get around this the team used a recently-developed technique involving studying lithium isotopes in marine limestone (this lithium could only come from weathering and is not changed by biological organisms).

The Ocean Anoxic Event 2 is believed to have been caused by a massive increase in volcanic activity in one of three regions: the Caribbean, Madagascar, or the Solomon Islands. The event saw the temperature of seawater around the equator warm by about 3 degrees Celsius. It is thought that this warming caused around 53% of marine species to go extinct. Animals like turtles, fish, and ammonites were amongst those severely affected.

'Everyone remembers the mass extinction of land animals caused by the K-T meteorite impact 30 million years later, thought to be responsible for the demise of the dinosaurs, but in many ways this was just as devastating for marine life,' said Dr Pogge von Strandmann. 'Whilst nutrients from weathering caused a population boom of some species near the surface of the oceans, it also led to a loss of oxygen to the deeper ocean, killing off over half of all marine species and creating a 'dead zone' of decaying animals and plants. It's a scenario we wouldn't want to see repeated today.

'Our research is good news, showing that the Earth can recover up to four times faster than we thought from CO₂ emissions, but even if we stopped all emissions today this recovery would still take hundreds of thousands of years. We have to start doing something soon to remove CO₂ from the atmosphere if we don't want to see a repeat of the kind of mass extinctions that global warming has triggered in the past.'

The research was supported by the UK's Natural Environment Research Council.

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