A doctor examines a mole on a patient's shoulder.

Doctors Finally Decide When a Mole Is Benign and When It's Cancerous

<p>
 For over 30 years, cancer researchers have argued about moles.
</p>
<p>
 Specifically, they’ve debated at what point a skin lesion becomes a melanoma, more commonly known as skin cancer. Some claimed that lesions which looked halfway between a benign mole and a melanoma make up a class of their own, while others held that lesions can only be either harmless or cancerous, with no in-between.
</p>
<div class="ad"></div>
<p>
 Over 70,000 new melanomas will be diagnosed in the United States in 2015, according to the American Cancer Society. Recently, a team of researchers led by Hunter Shain of the University of California-San Francisco announced at the Society for Melanoma Research convention that they have new data that settles the debate—a better way of telling whether a lesion is on track for becoming melanoma.
</p>
<p>
 Intermediate lesions, Shain said, “are very difficult to study simply because they are difficult to identify,” Shain said. Their appearance lies in a gray zone between obviously benign and obviously malignant. When Shain and the team had eight expert dermatologists try to classify them, there was little agreement.
</p>
<div class="related"></div>
<p>
 To get around this problem, the team devised a clever solution, using a characteristic of skin cancer to their advantage. Mature melanomas often lie next to skin tissue that represents earlier stages of the lesion. Taking 37 samples of melanomas from patients, the scientists micro-dissected them into their component sections—healthy skin, precursor lesion, possibly intermediate lesion, and mature melanoma.
</p>
<p>
 The researchers sequenced nearly 300 cancer-related genes in each section of the samples to discover which genes changed at which stage of development. They found that intermediate lesions had some harmless mutations but also some genetic changes that could lead to cancerous cell growth. That told them those lesions did not just look in between—their DNA actually made their behavior intermediate between a mole and a melanoma.
</p>
<p>
 The team presented their work
 <a href="http://www.melanomacongress.com/">
  at the melanoma convention
 </a>
 last month and
 <a href="http://www.nejm.org/doi/full/10.1056/NEJMoa1502583">
  published the full version of the project
 </a>
 in the New England Journal of Medicine.
</p>
<p>
 Sorting out the genetic gray zone also gave them a clearer view of how a melanoma develops. “In our study, we observe the canonical order of mutations that allow a melanocyte [a skin cancer cell] to overcome these barriers as it progresses to melanoma,” Shain said.
</p>
<p>
 In the 1980s, some researchers described an intermediate lesion as a “dysplastic nevus,” while others argued that the term would lead to confusions in melanoma diagnosis and shouldn’t be used. Shain’s team avoided using the term “dysplastic nevus.”
</p>
<p>
 David Elder of the University of Pennsylvania, who coined the term “dysplastic nevus syndrome” in 1980, attended the team’s presentation in San Francisco. “I think this is an important step forward,” Elder said. “And it does add materially to our understanding of a question that has certainly been hotly debated in our community for many years.”
</p>
<p>
 While the study’s authors didn’t use his terminology, Elder said they are basically describing the same thing. He said that at the presentation, “I asked the question, ‘Were these intermediate lesions dysplastic nevi or were they something else?’ And the response was, ‘Well, yes, they are.’” Elder agreed that using the term could distract from the study’s main message.
</p>
<p>
 Iwei Yeh of UC-San Francisco, a co-author of the study and one of the eight expert dermatologists, said that the new genetic data will allow the next stage of research to narrow the list of suspects for which mutations are most likely to lead to melanoma. Researchers could observe people with intermediate lesions and see which ones develop cancer. Then, they could use those genes as diagnostic signals for a mole on track to become malignant.
</p>
<p>
 “I think that kind of ties into this whole idea of personalized medicine,” Yeh said. “What are the individual alterations that are really contributing to the person’s cancer, and what does that mean for them in terms of their outcome?”
</p>
<p>
 Elder said this kind of study could reduce unnecessary procedures to remove harmless moles, saving time for both doctors and patients.
</p>
<p>
 “More precise diagnosis could be very valuable in more appropriate precision treatment of these lesions,” he said. “If you don’t need to do [a procedure], you don’t want to do it.”
</p>
<div class="newsletter"></div>
<p>
 Photo credit: NIH
</p>

<p>By closely examining a range of moles and sequencing their genomes, doctors now know how moles progress to cancer.</p>

The Bacteria That Help Bears Hibernate Could Help Cancer Patients

<section class="entry-content instapaper_body clearfix" itemprop="articleBody">
<div class="add-container clearfix" id="add-block-placer">
</div>
<p>
  If you’ve ever thought it might be nice to just sleep through February, good news: scientists have come one step closer to understanding how bears do it.
 </p>
<p>
  It’s long been known that bears slow down their cells’ energy use during the winter to survive on little food.  But scientists recently discovered that it’s not just the bear’s own cells that make hibernation happen—bacteria in the bears’ guts play an important role in both putting on fat in summer and slowing down their glucose use in winter.
 </p>
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/bear_h7RSZbY.width-990_6xgBXnl.jpg"/>
<figcaption>A brown bear scratches its head.
        
    </figcaption>
</figure>
<p>
  Biologists in Sweden partnered with the Scandinavian Brown Bear Research Project to take fecal samples from tranquilized bears in the summer and winter. These samples contained the collection of bacteria, or microbiome, that lives in the bears’ intestines and helps them absorb nutrients. Then they transferred the microbiome to lab mice with no bacteria in their guts to see how it affected how fast the mice gained fat tissue.
 </p>
<p>
  In the summer, bears chow down on a broad diet of salmon, insects, and berries. These foods don’t just give them fuel—some carry specialized bacteria that help them break down and absorb fat in their food. The researchers found that the mice with “summer bear” bacteria packed on more fat compared to mice given the winter microbiome.
 </p>
<p>
  In the winter, bears don’t eat for up to six months, and the diversity of bacteria species in their intestines dwindles. Lots of fat tissue tends to cause animals to keep sugar circulating in their blood—as in diabetes. Bears with extra winter fat were able to slow down their sugar consumption, but in the summer they could both gain weight and use glucose normally—an unusual and helpful adaptation.
 </p>
<p>
  Are there lessons we can take from the bear’s gut that we could use to help humans with diet problems? It’s possible. Here’s what the study author Fredrik Bäckhed, from the University of Gothenburg in Sweden,
  <a href="http://www.bbc.com/news/science-environment-35441712">
   told
  </a>
  Jonathan Webb of BBC News:
 </p>
<blockquote>
<p>
   “I don’t think that this study will have direct implications for obesity, as the summer microbiota will make you fat and the winter insulin resistant.
  </p>
<p>
   “But perhaps we can find clues for treating malnutrition from the summer bacteria, and help patients with anorexic disorders – including cancer patients.”
  </p>
</blockquote>
<p>
  For more on bears’ winter sleep, check out our guide to
  <a href="http://www.pbs.org/wgbh/nova/nature/bear-essentials-of-hibernation.html">
   the bear essentials of hibernation.
  </a>
</p>
</section>
<p>
 Photo credit:
 <a href="https://www.flickr.com/photos/tambako/4283191966/in/photolist-7wutKm-vdzm2G-ykXgsw-g6MaYR-wMsfNm-kCELRJ-8AyWGY-an7oJ1-fapdiA-dV2sGu-y7K1sv-rugNBW-bQeU2t-s1PTs9-oHjMue-6yDjXw-59d27A-59daXJ-9ESqyc-932gbp-nEBsSx-qQFq4E-dis9Sy-uJVtHs-xnNVm2-nVK3cA-hbY99m-h4xz3i-ge6NBe-tRiQjA-nUq3VB-hNxPK9-dUMkSK-pS4wTT-3c7fEK-p8UVE8-nQHq8U-AhWv46-8xFjMV-4tYzm7-68L1EY-w47yQA-wfRUj9-gsPJ9A-jcbV1L-AebNkS-6TihYH-cJMXEd-A5czeL-hhc55v">
  Tambako the Jaguar/Flickr (CC BY ND 2.0)
 </a>
</p>

The Search for Superorganisms

<section class="entry-content instapaper_body clearfix" itemprop="articleBody">
<div class="add-container clearfix" id="add-block-placer">
</div>
<p>
  In 2009, Victoria Orphan crammed into the submarine Alvin with a pilot and another marine scientist to see an ecosystem as strange and separate as another planet.
 </p>
<p>
  They dipped below the surface in the Caribbean Sea near Costa Rica, where the North American continent is pushing the oceanic plate into the Earth’s searing-hot mantle. There, the shifting geology is destabilizing an undersea mountain, causing it to spew methane gas and sulfides from deep-sea vents. Descending down the water column, they soon passed beyond the reach of sunlight. At first, when Alvin’s spotlights touched the seafloor, the scientists saw nothing but ocean mud through the windows, with maybe a sea cucumber here and there. As they got closer to the methane seeps, they saw what looked like pavement: a rocky build-up of carbon over the mud. Then, Orphan saw something remarkable.
 </p>
<p>
  “When we came up on the site—I’ll never forget that—there were teams of these crabs, and they were all waving their arms over the sulfide coming out of the vents,” Orphan says. “Crabs dancing on the seafloor was definitely a memorable sight.”
 </p>
<p>
  The crabs’ arms are laden with bacteria that are able to eat the sulfide chemicals from the vents. Every so often, the crabs eat the bacteria off their arms—a farm that fits on a claw.
 </p>
<p>
  Orphan, a marine geobiologist at the California Institute of Technology, says that this entire alien ecosystem depends on a partnership between two very different kinds of single-celled microbes: a species of archaea and a species of bacteria. They’re more different from each other than humans are from plants.
 </p>
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/superorganisms.width-990_MAfPqmz.png"/>
<figcaption>Microbes that act as superorganisms have evolved to be deeply dependent on one another.
        
    </figcaption>
</figure>
<p>
  In the deep-sea vents, they can form a superorganism greater than the sum of its parts. Microbes that act as superorganisms have evolved to be deeply dependent on each other instead of competing. And this cooperation lets them survive in extreme places. Working together, the microbes are able to eat the methane from the seeps. In the process, they cause dissolved carbon molecules in the water to solidify on the seamount, accumulating into the rocky pavement. And that hard surface creates a base on which all the larger creatures, including the farmer-crabs, can survive.
 </p>
<p>
  Partnerships like this one aren’t just far away in the deep ocean—they’re also in our landfills and backyard ponds. And the bizarre way in which these microbes cooperate tells us something about what we might expect to find when we search for life on other planets.
 </p>
<h2>
  An Extreme Partnership for an Extreme Place
 </h2>
<p>
  The ways that simple, single-celled bacteria and archaea interact with each other are more complex than scientists ever imagined, and biologists only recently discovered a surprising partnership between two very different microbes that team up to survive the harshest of environments.
 </p>
<p>
  All life is powered by chemical reactions. On land and in the shallows of the ocean, organisms use light from the sun to power the photosynthetic reactions that form the base of the food web. But at the bottom of the ocean, there’s no light—only gases and hot fluids seeping from Earth’s crust. If life is to survive, it has no choice but to use them. There, an organism’s choices for chemicals to react are pretty limited. Two of the common chemicals leaking from the vents, methane and sulfate, can combine to produce carbonate, sulfide, and a little energy. Under normal undersea conditions, making this reaction happen is like climbing a mountain.
 </p>
<p>
  But microbes have found a way around the mountain through working together. Archaea cells cluster together in a sphere of about 100 cells. They take in methane gas and break it down, grabbing electrons from the molecules to power their life cycle. But if too much electric charge builds up within the cell, the process stops. It’s like a bucket line with nowhere to put the last bucketful: the line gets jammed. The archaea need to dump the electrons somewhere.
 </p>
<p>
  That’s where the bacteria partners come in. About 200 of those cells cluster around the inner sphere of archaeal cells. The archaea pass the extra electrons to the bacteria, which use the electrons to power their own reaction. They absorb sulfates from the deep-sea vent and add electrons to them, producing sulfide and a little bit of energy.
 </p>
<p>
  It’s a process called syntrophy, which literally means “feeding together.” Together, the sphere of cells makes a complete reaction and produces enough energy so both archaea and bacteria can survive.
 </p>
<p>
  Even the way in which they share electrons gave scientists a surprise. Last year, biologists at the Max-Planck Institute for Marine Microbiology found that the two species use tiny nanowires that carry electric current from the archaea to the bacteria.
 </p>
<p>
  The nanowires form “an electrical bridge between organisms,” says James Holden, a marine biologist at the University of Massachusetts-Amherst, who wasn’t involved in the study. This creates “a really tight, tight relationship.” We knew this could happen between two species of bacteria—but not two organisms as different as archaea and bacteria. It’s as though you and your petunias shared a physical connection.
 </p>
<p>
  “They are like a very old couple—one cannot [live] without the other,” says Gunter Wegener, a researcher at the Max Planck institute and the first author of the 2015 paper. “We can clearly speak of a superorganism, as the survival of the genomic information of one organism clearly depends on the other.”
 </p>
<p>
  Orphan says that while she’s been able to show that these two species can survive on their own, given the right conditions in the lab, this might be like growing human tissue on a culture plate that couldn’t really live on its own.
 </p>
<aside class="pulledquote">
  “It’s almost like everywhere you look, you start to see evidence of these interdependencies.”
 </aside>
<p>
  This isn’t the only way that microbes can link themselves, either. In the hydrothermal vents that Holden studies off the coast of Oregon, water heated by magma and carrying sulfides and dissolved metals gushes out of chimneys on the seafloor. The water can reach a sweltering 700° F. There, a different kind of cooperation has evolved.
 </p>
<p>
  Two archaea species at the hot vents actually do the reverse of what the microbial superorganisms do at the methane seeps. Instead of breaking down methane, they work together to build it. One archaeon eats chemicals coming out of the vent, producing hydrogen gas as waste. If too much of it built up, it up would stop the reaction.
 </p>
<p>
  That’s where the partner microbe comes in. This other archaeon clusters close to the one producing hydrogen to gobble up every bit, combining it with carbon atoms to make methane gas and a little bit of energy. Normally, this reaction wouldn’t be energetically favorable at the bottom of the ocean. But by working together, the two microbes make this unlikely process possible.
 </p>
<p>
  “The reaction just doesn’t want to go forward by itself,” Holden says. “So the only way you can cheat thermodynamics is if you tilt the scales.” Cooperating lets the microbes survive.
 </p>
<p>
  But these kinds of extreme partnerships aren’t limited to the bottom of the ocean. “It’s almost like everywhere you look, you start to see evidence of these interdependencies,” Orphan says. They extend beyond extreme environments to the seemingly benign backyard ecosystems.
 </p>
<h2>
  Superorganisms in Your Backyard
 </h2>
<p>
  In fact, while we’re just now figuring out how these superorganisms work, even the United States’ first president saw their effects on the environment. After winning the Revolutionary War, George Washington became free to pursue his scientific hobbies. Benjamin Franklin and another scientist had been arguing about a mysterious phenomenon, and Washington hoped to settle the debate. Franklin had found that if he lit a candle near the surface of a stream, it would catch fire and “burn for near half a minute.” The two couldn’t decide what could cause this, and Washington, along with writer Thomas Paine, boarded a boat on a nearby creek to figure it out.
 </p>
<p>
  Paine argued that flammable gases constantly bubbled up from streams, while Washington believed that flammable gases rose only when rowers disturbed the bottom of the stream. They sat at either end of a boat holding burning rolls of paper. Sure enough, when the soldiers rowing the boat stirred up the creek mud, fire descended from Washington’s paper to the surface then spread around the boat.
 </p>
<p>
  While they could not have known at the time, the gas they stirred up was methane produced by superorganisms—two kinds of archaea partnering to survive in an environment without oxygen.
 </p>
<p>
  It’s not just backyard ponds and creeks, either. Huge flames sometimes burst from landfills when lots of methane builds up and ignites. Elsewhere, methane-producing archaea live in wastewater treatment plants, rice fields, oil spills, and the bellies of cows. The same reaction-sharing strategy as in the deep-sea seeps has let them adapt to both human-built ecosystems and the insides of other creatures.
 </p>
<p>
  In these partnerships, one set of archaea cells takes in carbon-containing compounds and breaks off hydrogen groups, gaining electrons to eat and producing hydrogen gas as a waste. It passes the hydrogen to the partner cells, which then builds methane molecules from the hydrogen gas and carbon dioxide. By keeping the concentration of hydrogen low, the second partner keeps the whole system running.
 </p>
<p>
  “Hydrogen syntrophy is a very, very common process on Earth,” Holden says. “Most of the methane that ends up in our atmosphere every year comes from this process.” The same partnership that makes life possible in a deep-sea hot vent allows life to flourish in a steaming landfill.
 </p>
<h2>
  How to Survive on Mars
 </h2>
<p>
  It turns out that microbes that can handle the heat hydrothermal vent on Earth can also probably brave the cold of the Martian surface or the moons of Jupiter.
 </p>
<p>
  In 2006, scientists at the Maryland Astrobiology Consortium took a strain of archaea from a salty lake in Antarctica and tested it to see just how much cold and salt it could handle before its methane production shut down. They found that, at 28˚ F, around the freezing point of very salty water, the hardy microbe clumped together to share resources, kept eating their chemical food, and even grew their ranks.
 </p>
<p>
  To stick together, the archaea cells connected to each other with tiny fibers. The scientists shook up the test tube to see how strong the aggregation was. While the shaking broke it up, the cells reformed their network of fibers within a day. The vibrations, salt, and cold all failed to stop the archaea.
 </p>
<aside class="pulledquote">
  Superorganisms show us that sometimes it pays to work together.
 </aside>
<p>
  On Mars, those almost-freezing temperatures only occur on the warm days. But microbes in Antarctica have shown that cells have ways of surviving when the temperature dips below the range in which they can grow and feed. They’re able to basically freeze-dry themselves to survive the cold and high salt concentrations that result when most of the water freezes.
 </p>
<p>
  The superorganisms we find on Earth suggest that if we ever find microbial life on another planet, it might not be just simple single-celled organisms living only for themselves. Being a good competitor, it turns out, isn’t always the best strategy. Superorganisms show us that sometimes it pays to work together.
 </p>
<p>
  “Certainly in a place like Mars, it’s a tough environment for a lot of different reasons,” Holden says. “But if there were or is microbial life on Mars, then it wouldn’t surprise me if there’s some sort of cooperation occurring between different types of organisms.”
 </p>
<h2>
  Extreme Cooperation
 </h2>
<p>
  From the depths of the ocean to our own backyards, bizarre relationships between microbes are changing how we understand life. We’re discovering that what it means to be an individual isn’t the same throughout the living world, says Matt Haber, a philosopher of biology at Utah State.
 </p>
<p>
  “Individuals come in degrees,” Haber says. There are individuals like cats and dogs, but there are also social organisms that act as individuals, like ant colonies and beehives. The deep-sea clumps of microbes seem to be a borderline case of individuality, since it doesn’t seem to reproduce as a unit. “This could be an example of ways that bacteria and archaea can interact that may be approaching individuality but hasn’t reached that level yet,” he says.
 </p>
<p>
  Still, they’re very tightly connected. “The unit looks like it’s acting as an individual, at least in some sense, in the way that they’re interacting with the environment,” Haber says.
 </p>
<p>
  “We’re kind of in a golden age of microbes right now,” Haber says. “We’re really beginning to appreciate how much they challenge our views of biology.”
 </p>
</section>
<p>
 Image credit: Max Planck Institute
</p>

From landfills to the deep sea, superorganisms are redefining life and our search for it on other planets.

This Stretchable, Bendable Sheet-Camera Could Prevent Future Car Accidents

<section class="entry-content instapaper_body clearfix" itemprop="articleBody">
<div class="add-container clearfix" id="add-block-placer">
</div>
<p>
  The eye of a housefly is made up of thousands of lenses. Engineers are now translating that design into a revolutionary new camera.
 </p>
<p>
  The idea of making a sheet camera has been around for a while, but there are challenges to making it work. When a sheet of fixed lenses bends, the lenses in the middle take incomplete images. Here’s how that happens: look at your hand with your fingers flat and together (as in, not spread apart). If each finger was the field of view for a single fixed lens, they take a complete image when they’re close together. But spread them apart—the equivalent of bending the camera sheet—and gaps emerge.
 </p>
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/bendy-camerause.width-990_Gl8b0P3.jpg"/>
<figcaption>When the sheet bends, the sheet camera’s lenses can stretch to form a complete image.
        
    </figcaption>
</figure>
<p>
  A team of researchers at Columbia University found
  <a href="http://www.cs.columbia.edu/CAVE/projects/flexible_sheet_cameras/Sims_ICCP16.pdf">
   a clever way around this problem
  </a>
  . They developed a lens that changes shape as the sheet curves. Made of silicone rubber, the lenses can spread out and increase their field of view when the sheet is bent.
 </p>
<p>
  The prototype they made is small scale, but the results are promising. Here’s Rachel Metz, reporting for Technology Review:
 </p>
<blockquote>
<p>
   First, they molded a very-low-resolution flexible lens array—just 33 by 33 lenses—in silicone rubber. Then they layered it atop a flexible sheet of plastic with holes in it and a diffusing sheet, and held all these layers in place in a sort of vise that could be used to bend them while a computer monitor projected images from above. While bending all the layers at various angles, researchers captured the images formed on the diffusing sheet (such as multicolored dots and a boy with a horse) with a digital camera that they set below the whole contraption.
  </p>
</blockquote>
<p>
  While the images were pretty blurry, the sheet camera was able to capture a full image, without gaps between what each lens can see.
 </p>
<p>
  The next step will be building a flexible screen capable of displaying wrap-around images as the camera bends. When the full system is set up, the developers hope the device can be used to give drivers a complete field of view, eliminating blind-spot hazards that cause accidents. It could even play a role in building a better self-driving car, giving the computer software driving the car a better visual of its surroundings.
 </p>
<div class="flex-video">
<iframe allowfullscreen="" frameborder="0" height="439" src="https://www.youtube.com/embed/7Z8EtlBe8Ts?feature=oembed" width="780">
</iframe>
</div>
<div class="inline-caption">
  Here’s another groundbreaking camera: one that can capture light in motion at a trillion frames per second.
 </div>
</section>
<p>
 Image credit: Computer Vision Laboratory, Columbia University
</p>

A String of Supernovae May Have Caused Earth’s Recent Ice Ages

<section class="entry-content instapaper_body clearfix" itemprop="articleBody">
<div class="add-container clearfix" id="add-block-placer">
</div>
<p>
  You may have thought Earth was safe from supernovae, the giant explosions from dying stars. Astronomers are now saying we should think again.
 </p>
<p>
  Two teams of scientists reached the same surprising conclusion: a cluster of supernova blasts rained radioactive iron on the Earth. One of them blew up as recently as 0.8 million years ago.
 </p>
<p>
  The road to this discovery began in 1999, when scientists took samples from the ocean’s crust, in a layer of rock that formed 2.2 million years ago. A radioactive isotope called iron-60 turned up in the samples. It’s an unstable atom with a short half-life. That means it’s a much younger atom than earthly elements. Had it been around when the planet took shape, it would have degraded long ago. Instead, it must have landed in the crust from outer space.
 </p>
<figure class="richtext-image full-width">
<img alt="Supernova illustrationUSE" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/supernova-illustrationuse.width-990_RJn2xog.jpg"/>
<figcaption>An illustration of the radioactive iron cloud from one of the supernovae.
        
    </figcaption>
</figure>
<p>
  Until recently, astronomers thought that this iron came from just one nearby supernova from an unknown direction. But the two new studies suggest that, in fact, a string of supernovae went off over the past 10 million years—just a blink of an eye in galactic terms. And two of them were near enough to hit Earth with radioactive particles.
 </p>
<p>
  Here’s Daniel Clery,
  <a href="http://www.sciencemag.org/news/2016/04/earth-barraged-supernovae-millions-years-ago-debris-found-moon">
   reporting
  </a>
  for Science Magazine:
 </p>
<blockquote>
<p>
   Their analysis suggests that two of those supernovae were close enough and recent enough to have contributed to iron-60 on Earth: the first 2.3 million years ago, the second 0.8 million years later; both about 300 light-years from Earth.
  </p>
<p>
   “We may never be able to identify [the individual stars],” comments Neil Gehrels, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, “but we can see the regions of intense star formation” where they lived and died.
  </p>
</blockquote>
<p>
  These supernovae weren’t close enough to incinerate life on Earth. But all that iron in the air may have changed the planet’s climate. The timing of the explosions happens to correspond to the transition into the
  <a href="http://www.ucmp.berkeley.edu/quaternary/pleistocene.php">
   Pleistocene epoch
  </a>
  , the icy glacial period dominated by mastodons, mammoths, and saber-toothed cats. It’s possible that the radioactive particles in the atmosphere could have seeded clouds—thereby increasing cloud cover—and contributed to the ice ages of the Pleistocene.
 </p>
<p>
  To sort out exactly where in the galaxy the explosions came from, it might take new missions to the moon. Since Earth’s moon has no atmosphere, particles from supernovae could still be positioned exactly as they were when they first fell. Astrophysicists could use iron-60 samples from the moon to point the way to their source.
 </p>
</section>
<p>
 Photo credit:
 <a href="http://www.pressestelle.tu-berlin.de/medieninformationen/2016/april_2016/medieninformation_nr_472016/">
  Michael Schulreich, TU Berlin
 </a>
</p>

Psychologists Discover Easy Ways to Make Standardized Testing Less Biased

<section class="entry-content instapaper_body clearfix" itemprop="articleBody">
<div class="add-container clearfix" id="add-block-placer">
</div>
<p>
  When Ahmed Mohamed, 14, was arrested in Texas for bringing the clock he made to school to show his teacher, he encountered just one of the many ways that students can suffer from stereotypes, especially in science and technology. Ethnic minorities and women often experience this pressure because they do not match expectations for what scientists looks like. But a new psychology experiment shows how stereotyped students can use that pressure to their advantage.
 </p>
<div class="wp-caption aligncenter" id="attachment_2307" style="max-width: 2058px">
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/brazil-standardized-test_cQIODc1.width-990_Ne8wGDh.jpg"/>
<figcaption>
</figcaption>
</figure>
<p class="wp-caption-text">
   High school students in Brazil take a national standardized test.
  </p>
</div>
<p>
  Deeply ingrained stereotypes like “girls can’t do math” tend to make people underperform. It’s an effect known as stereotype threat, which arises when people fear that they’ll confirm a negative stereotype about their group. Negative stereotypes about testing can lead to lower scores on standardized tests like the SAT and GRE, harming students’ chances of getting into top schools. Yet that stereotype threat can motivate students to score higher than their socially privileged peers, according to
  <a href="http://www.sciencedirect.com/science/article/pii/S0022103115000761" target="_blank">
   a study
  </a>
  coming out this November in the
  <em>
   Journal of Experimental Social Psychology
  </em>
  by psychology professors Allison Seitchik of Merrimack University and Stephen Harkins of Northeastern University.
 </p>
<p>
  “When they’re threatened, they can do better—as long as they know what to do,” Seitchik said.
 </p>
<p>
  The researchers handed women college students a 120-problem math test. For some students, the instructions read that the test “has been shown to produce gender differences.” Reading this was intended to induce stereotype threat. And indeed, when students were threatened, they solved 12 problems less on average than non-threatened students.
 </p>
<p>
  But when students were threatened and also told to use a more efficient problem solving method, they not only did as well, they correctly answered 13 more problems than non-threatened students also told to use the better method—reversing stereotype threat’s usual effect.
 </p>
<p>
  “I thought it was pretty cool that [we]were finding the opposite of what people had found with stereotype threat,” Seitchik said. “If you just tweak their approach…you eliminate the stereotype threat effect.”
 </p>
<p>
  Seitchik used the same experimental design as other studies of stereotype threat, but took things a step further to look at specific problem solving strategies.
 </p>
<p>
  While psychologists have documented the stereotype threat’s effects, they still disagree on the mental process that causes it. Some argue that worries about confirming a negative stereotype take up short-term memory space which could be used for problem solving. This is called the working memory explanation.
 </p>
<p>
  Other psychologists claim that, first and foremost, stereotyped students want to beat expectations, and that it’s this extra effort which traps them. This is known as the mere effort explanation. Giving the test their all, stereotyped students tend to choose problem solving strategies they trust most instead of the most efficient ones. Students then try to solve the whole problem on math tests instead of using logic to eliminate wrong answers—ultimately slowing them down.
 </p>
<p>
  “In this study, the authors beautifully identified a situation” where the mere effort model explains stereotype threat, said University of Waterloo psychology professor Christine Logel, who co-wrote
  <a href="http://www.annualreviews.org/doi/abs/10.1146/annurev-psych-073115-103235" target="_blank">
   a recent review
  </a>
  of stereotype threat studies. But in other situations in which stereotypes are in play, the way stereotype threat works could depend on many other factors, she said.
 </p>
<p>
  Seitchik’s experiment showed a way to make tests better reflect the students’ true abilities. Instructing students on the best test-taking methods—for example, using logic to eliminate answers—lets them put their extra effort to its best use.
 </p>
<p>
  “If we can do this with females that are younger…then we can keep them in STEM,” Seitchik said.
 </p>
<p>
  But these findings are not just relevant for gender stereotypes. It works the same for students of any gender facing negative ethnic stereotypes about academic performance. For any stereotyped group, if researchers find the problem-solving method students use when trying their hardest, a simple instruction to use a different one can raise scores, Seitchik said.
 </p>
<p>
  Another way to make tests more accurate assessments of ability is to stop asking questions about gender and ethnicity before standardized exams, Seitchik said. Though this would not eliminate stereotype threat, it could lessen it.
 </p>
<p>
  “Don’t ask students’ race and gender in the front page of the test,” Logel said. “It’s like flashing a neon sign that says, ‘Race is a factor on this test. Gender is a factor.’ ”
 </p>
<p>
<i>
   This article originally appeared on
  </i>
<a href="http://www.pbs.org/wgbh/nova/next/body/psychologists-discover-easy-ways-to-make-standardized-testing-less-biased/" target="_blank">
   NOVA Next
  </a>
  .
 </p>
</section>

Newest Fusion Reactor Is a Relic of a Cold War Tech Rivalry

<section class="entry-content instapaper_body clearfix" itemprop="articleBody">
<div class="add-container clearfix" id="add-block-placer">
</div>
<p>
  Plans left over from an unfinished Cold War tech rivalry could help meet the world’s clean energy needs.
 </p>
<p>
  Today, the Max Planck Institute in Greifswald, Germany, started up a nuclear fusion reactor using hydrogen fuel, the Associated Press reports. German Chancellor Angela Merkel, herself a former physicist, ceremoniously pushed the button. But the basic design of the new reactor is as old as the color TV.
 </p>
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/w7x_plasma_2.tif.width-990_FkRYNSk.jpg"/>
<figcaption>Photo of the plasma generated today in the Wendelstein 7-X.
        
    </figcaption>
</figure>
<p>
  Scientists have struggled to build a bug-free fusion reactor since the 1950s. The original Soviet model, a bagel-shaped device called a tokamak, is relatively simple to build and is the same design that underpins the massive ITER reactor under construction in France. Using powerful magnetic fields, the machine superheats hydrogen gas until it becomes plasma. At this point, the hydrogen atoms begin fusing into helium.
 </p>
<p>
  Not to be outdone by the Soviets, the Americans had their own fusion research program. Lyman Spitzer of Princeton University designed the American alternative in 1951. Dubbed the stellarator, the extra magnetic coils that wind their way around the outside of the tube keep the plasma fuel under better control, but they make for a much more complicated design.
 </p>
<p>
  So far, both models have had problems. For tokamaks, the plasma current tends to halt unexpectedly, causing powerful electric fields to escape and damage the reactor, and for stellerators,  construction costs have kept most on the drawing board. But the Planck Institute is giving the stellarator blueprint another shot.
 </p>
<p>
  The Institute’s reactor, called the Wendelstein 7-X, has been under construction since 1993—it was “hell on Earth” to build, the project’s leader
  <a href="http://www.sciencemag.org/news/2015/10/bizarre-reactor-might-save-nuclear-fusion">
   told
  </a>
  Science. The first test run was completed in December using helium fuel, which is easier to heat than hydrogen, the standard fuel. At today’s event, the Associated Press
  <a href="http://www.theguardian.com/environment/2016/feb/03/nuclear-fusion-germany-scientists-experiment-angela-merkel">
   spoke
  </a>
  to physics professor David Anderson of the University of Wisconsin, who was optimistic about that first test:
 </p>
<blockquote>
<p>
   “The impressive results obtained in the startup of the machine were remarkable,” he said. “This is usually a difficult and arduous process. The speed with which W7-X became operational is a testament to the care and quality of the fabrication of the device and makes a very positive statement about the stellarator concept itself. W7-X is a truly remarkable achievement and the worldwide fusion community looks forward to many exciting results.”
  </p>
</blockquote>
<p>
  Today’s test smashed hydrogen atoms together to produce superheated plasma—but only for a fraction of a second. The Wendelstein 7-X isn’t set up to provide power to northeastern Germany—it’s just testing the design for future reactors. It could be decades before stellarators replace other power sources.
 </p>
</section>
<p>
 Photo credit: IPP
</p>

Conor Gearin

Articles