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‘The era of neutrino astronomy has begun’

Astrophysicists using a telescope embedded in Antarctic ice have succeeded in a quest to detect and record the mysterious phenomena known as cosmic neutrinos -- nearly massless particles that stream to Earth at the speed of light from outside our solar...
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Improve learning by taming instructional complexity

Nov. 21, 2013 — From using concrete or abstract materials to giving immediate or delayed feedback, there are rampant debates over the best teaching strategies to use. But, in reality, improving education is not as simple as choosing one technique over another.

Carnegie Mellon University and Temple University researchers scoured the educational research landscape and found that because improved learning depends on many different factors, there are actually more than 205 trillion instructional options available.

In the Nov. 22 issue of Science, the researchers break down exactly how complicated improving education really is when considering the combination of different dimensions -- spacing of practice, studying examples or practicing procedures, to name a few -- with variations in ideal dosage and in student needs as they learn. The researchers offer a fresh perspective on educational research by focusing on conclusive approaches that truly impact classroom learning.

The findings were published only a week after CMU launched the Simon Initiative to accelerate the use of learning science and technology to improve student learning. Named to honor the work of the late Nobel Laureate and CMU Professor Herbert Simon, the initiative will harness CMU's decades of learning data and research to improve educational outcomes for students everywhere.

"There are not just two ways to teach, as our education debates often seem to indicate," said lead author Ken Koedinger, professor of human-computer interaction at Carnegie Mellon, director of the Pittsburgh Science of Learning Center (PSLC) and co-coordinator of the Simon Initiative. "There are trillions of possible ways to teach. Part of the instructional complexity challenge is that education is not 'one size fits all,' and optimal forms of instruction depend on details, such as how much a learner already knows and whether a fact, concept, or thinking skill is being targeted."

For the paper, Koedinger, Temple's Julie Booth and CMU's David Klahr investigated existing education research to show that the space is too vast, with too many possibilities for simple studies to determine what techniques will work for which students at different learning points.

"As learning researchers, we get frustrated when our work doesn't seem to make an impact on the education system," said Booth, assistant professor of educational psychology at Temple who received her Ph.D. in psychology from Carnegie Mellon. "But much of the work on these learning principles has been conducted in laboratory settings. We need to shift our focus to determine when and for whom these techniques work in real-world classrooms."

To tame instructional complexity and maximize the potential of improving research behind educational practice and student learning, the researchers offer five recommendations:

1. Because trying all educational options -- more than 205 trillion -- to find out what works best is impossible, research should focus on how different forms of instruction meet different functional needs, such as which methods are best for learning to remember facts, which are best for learning to induce general skills, and which are best for learning to make sense of concepts and principles.

2. More experiments are needed to determine how different instructional techniques enhance different learning functions. For example, the optimal way to memorize facts may be a poor way to learn to induce general skills.

3. Take advantage of educational technology to further understand how people learn and which instructional dimensions can or cannot be treated independently by conducting massive online studies, which use thousands of students and test hundreds of variations of instruction at the same time.

4. To understand impact, build a national data infrastructure in which data collected at a moment-by-moment basis (i.e., cognitive tutors tracking daily how a student learns algebra over a school year) can be linked with longer-term results, such as state exams and performances in a next class.

5. Create more permanent school and research partnerships to facilitate interaction between education, administration and researchers. For example, the PSLC, funded by the National Science Foundation (NSF), gives teachers immediate feedback and allows researchers to explore only relevant theories.

"These recommendations are just one of the many steps needed to nail down what's necessary to really improve education and to expand our knowledge of how students learn and how to best teach them," said Klahr, the Walter Van Dyke Bingham Professor of Psychology at CMU who directs PIER, the university-wide graduate training program in education research. "They're also in line with how Carnegie Mellon -- an educational research powerhouse -- approaches education by studying the intersection of instruction, cognitive psychology, computer science, statistics, philosophy and policy."

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Black hole birth captured: Biggest, brightest to happen in at least 20 years

Nov. 21, 2013 — Intelligent telescopes designed by Los Alamos National Laboratory got a front row seat recently for an unusual birth.

"Los Alamos' RAPTOR telescopes in New Mexico and Hawaii received a very bright cosmic birth announcement for a black hole on April 27," said astrophysicist Tom Vestrand, lead author of a paper appearing today in the journal Science that highlights the unusual event.

"This was the burst of the century," said Los Alamos co-author James Wren. "It's the biggest, brightest one to happen in at least 20 years, and maybe even longer than that."

The RAPTOR (RAPid Telescopes for Optical Response) system is a network of small robotic observatories that scan the skies for optical anomalies such as flashes emanating from a star in its death throes as it collapses and becomes a black hole -- an object so dense that not even light can escape its gravity field. This birth announcement arrived from the constellation Leo in the form of an exceptionally bright flash of visible light that accompanied a powerful burst of cosmic gamma-ray emissions.

What made such an extremely rare event even more spectacular for scientists, however, is that, in addition to the RAPTOR sighting, it was witnessed by an armada of instruments -- including gamma-ray and X-ray detectors aboard NASA's Fermi, NuSTAR and Swift satellites. While the NASA instruments recorded some of the highest-energy gamma-ray bursts ever measured from such an event, RAPTOR noticed that the massive and violent transformation of a star into a black hole yielded a lingering "afterglow" that faded in lock-step with the highest energy gamma-rays.

"This afterglow is interesting to see," said paper co-author Przemek Wozniak of Los Alamos's Intelligence and Space Research Division. "We normally see a flash associated with the beginning of an event, analogous to the bright flash that you would see coinciding with the explosion of a firecracker. This afterglow may be somewhat analogous to the embers that you might be able to see lingering after your firecracker has exploded. It is the link between the optical phenomenon and the gamma-rays that we haven't seen before, and that's what makes this display extremely exciting."

All things considered, the event was among the brightest and most energetic of its type ever witnessed.

"This was a Rosetta-Stone event that illuminates so many things -- literally," Vestrand said. "We were very fortunate to have all of the NASA and ground-based instruments seeing it at the same time. We had all the assets in place to collect a very detailed data set. These are data that astrophysicists will be looking at for a long time to come because we have a detailed record of the event as it unfolded."

Already the event, labeled GRB 130427A by astrophysicists, is testing some long-held assumptions about the nature of the universe. For example, scientists recorded energy levels for gamma rays that are higher than what some researchers thought theoretically possible. This revelation may require physicists to modify existing theories about radiation. No doubt, the data set could yield more surprises in the future, Vestrand said.

Science

How flu evolves to escape immunity

Nov. 21, 2013 — Scientists have identified a potential way to improve future flu vaccines after discovering that seasonal flu typically escapes immunity from vaccines with as little as a single amino acid substitution. Additionally, they found these single amino acid changes occur at only seven places on its surface -- not the 130 places previously believed. The research was published today, 21 November, in the journal Science.

"This work is a major step forward in our understanding of the evolution of flu viruses, and could possibly enable us to predict that evolution. If we can do that, then we can make flu vaccines that would be even more effective than the current vaccine," said Professor Derek Smith from the University of Cambridge, one of the two leaders of the research, together with Professor Ron Fouchier from Erasmus Medical Center in The Netherlands.

The flu vaccine works by exposing the body to parts of inactivated flu from the three major different types of flu that infect humans, prompting the immune system to develop antibodies against these viruses. When exposed to the actual flu, these antibodies can eliminate the flu virus.

However, every two or three years the outer coat of seasonal flu (made up of amino acids) evolves, preventing antibodies that would fight the older strains of flu from recognising the new strain. As a result, the new strain of virus escapes the immunity that has been acquired as a result of earlier infections or vaccinations. Because the flu virus is constantly evolving in this way, the World Health Organisation meets twice a year to determine whether the strains of flu included in the vaccine should be changed.

For this study, the researchers created viruses which had a variety of amino acid substitutions as well as different combinations of amino acid substitutions. They then tested these viruses to see which substitutions and combinations of substitutions caused new strains to develop.

They found that seasonal flu escapes immunity and develops into new strains typically by just a single amino acid substitution. Until now, it was widely believed that in order for seasonal flu to escape the immunity individuals acquire from previous infections or vaccinations, it would take at least four amino acid substitutions.

They also found that such single amino acid changes occurred at only seven places on its surface -- all located near the receptor binding site (the area where the flu virus binds to and infects host cells). The location is significant because the virus would not change so close to the site unless it had to, as that area is important for the virus to conserve.

"The virus needs to conserve this, its binding site, as it uses this site to recognize the cells that it infects in our throats," said Bjorn Koel, from Erasmus Medical Center in The Netherlands and lead author of the paper.

Seasonal flu is responsible for half a million deaths and many more hospitalizations and severe illnesses worldwide every year.

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Two Y genes can replace the entire Y chromosome for assisted reproduction in mice

Nov. 21, 2013 — The Y chromosome is a symbol of maleness, present only in males and encoding genes important for male reproduction. But live mouse offspring can be generated with assisted reproduction using germ cells from males with the Y chromosome contribution limited to only two genes: the testis determinant factor Sry and the spermatogonial proliferation factor Eif2s3y.

"Does this mean that the Y chromosome (or most of it) is no longer needed? Yes, given our current technological advances in assisted reproductive technologies," said Monika A. Ward, Associate Professor at the Institute for Biogenesis Research, John A. Burns School of Medicine, University of Hawai'i. At the same time, however, she also emphasized the importance of the Y chromosome for normal, unassisted fertilization and other aspects of male reproduction.

In a new manuscript scheduled for online publication in the journal Science on November 21, 2013, Ward and her UH colleagues describe their effort to identify the minimum Y chromosome contribution required to generate a healthy first generation mouse, capable of reproducing a second generation on its own without further technological intervention.

For this study, Ward and her colleagues used transgenic male mice with only two Y genes, Sry and Eif2s3y. The mice were considered infertile because they had meiotic and postmeiotic arrests -- that is, the germ cells that should have normally developed into sperm did not fully mature in these mice -- but researchers were able to find few usable cells. Yasuhiro Yamauchi, a post-doctoral scholar on Ward's team, harvested these immature spermatids and used a technique called round spermatid injection (ROSI) to successfully fertilize oocytes in the laboratory. When the developed embryos were transferred to female mouse surrogate mothers, live offspring were obtained.

Because the overall efficiency of ROSI with two Y genes was lower than with regular, fertile mice, the researchers then looked to see whether the addition of other Y genes could improve it. They increased the live offspring rate by about two-fold when Sry was replaced with the sex reversal factor Sxrb, which encodes three additional Y genes. These results demonstrated that Sxrb encodes a gene or genes that enhance the progression of spermatogenesis.

The study's findings are relevant but not directly translatable to human male infertility cases. In the era of assisted reproduction technologies, it is now possible to bypass several steps of normal human fertilization using immotile, non-viable, or immature sperm. At present, ROSI is still considered experimental due to concerns regarding the safety of injecting immature germ cells and other technical difficulties. The researchers hope that the success of ROSI in mouse studies may serve to support this approach as a viable option for overcoming infertility in men in the future.

As for the human Y chromosome, the researchers agree that it's not on its way to oblivion. Its genetic information is important for developing mature sperm and for its function in normal fertilization. The same is true for mice.

"Most of the mouse Y chromosome genes are necessary for normal fertilization," Ward said. "However, when it comes to assisted reproduction, our mouse study proves that the Y chromosome contribution can be brought to a bare minimum. It may be possible to eliminate the mouse Y chromosome altogether if appropriate replacements are made for those two genes."

Science

The era of neutrino astronomy has begun

Nov. 21, 2013 — Astrophysicists using a telescope embedded in Antarctic ice have succeeded in a quest to detect and record the mysterious phenomena known as cosmic neutrinos -- nearly massless particles that stream to Earth at the speed of light from outside our solar system, striking the surface in a burst of energy that can be as powerful as a baseball pitcher's fastball. Next, they hope to build on the early success of the IceCube Neutrino Observatory to detect the source of these high-energy particles, said Physics Professor Gregory Sullivan, who led the University of Maryland's 12-person team of contributors to the IceCube Collaboration.

"The era of neutrino astronomy has begun," Sullivan said as the IceCube Collaboration announced the observation of 28 very high-energy particle events that constitute the first solid evidence for astrophysical neutrinos from cosmic sources.

By studying the neutrinos that IceCube detects, scientists can learn about the nature of astrophysical phenomena occurring millions, or even billions of light years from Earth, Sullivan said. "The sources of neutrinos, and the question of what could accelerate these particles, has been a mystery for more than 100 years. Now we have an instrument that can detect astrophysical neutrinos. It's working beautifully, and we expect it to run for another 20 years."

The collaboration's report on the first cosmic neutrino records from the IceCube Neutrino Observatory, collected from instruments embedded in one cubic kilometer of ice at the South Pole, was published Nov. 22 in the journal Science.

"This is the first indication of very high-energy neutrinos coming from outside our solar system," said University of Wisconsin-Madison Physics Professor Francis Halzen, principal investigator of IceCube. "It is gratifying to finally see what we have been looking for. This is the dawn of a new age of astronomy."

"Neutrinos are one of the basic building blocks of our universe," said UMD Physics Associate Professor Kara Hoffman, an IceCube team member. Billions of them pass through our bodies unnoticed every second. These extremely high-energy particles maintain their speed and direction unaffected by magnetic fields. The vast majority of neutrinos originate either in the sun or in Earth's own atmosphere. Far more rare are astrophysical neutrinos, which come from the outer reaches of our galaxy or beyond.

The origin and cause of astrophysical neutrinos are unknown, though gamma ray bursts, active galactic nuclei and black holes are potential sources. Better understanding of these neutrinos is critically important in particle physics, astrophysics and astronomy, and scientists have worked for more than 50 years to design and build a high-energy neutrino detector of this type.

IceCube was designed to accomplish two major scientific goals: measure the flux, or rate, of high-energy neutrinos and try to identify some of their sources. The neutrino observatory was built and is operated by an international collaboration of more than 250 physicists and engineers. UMD physicists have been key collaborators on IceCube since 2002, when its unique design was devised and construction began.

IceCube is made up of 5,160 digital optical modules suspended along 86 strings embedded in ice beneath the South Pole. The National Science Foundation-supported observatory detects neutrinos through the tiny flashes of blue light, called Cherenkov light, produced when neutrinos interact in the ice. Computers at the IceCube laboratory collect near-real-time data from the optical sensors and send information about interesting events north via satellite. The UMD team designed the data collection system and much of IceCube's analytic software. Construction took nearly a decade, and the completed detector began gathering data in May 2011.

"IceCube is a wonderful and unique astrophysical telescope -- it is deployed deep in the Antarctic ice but looks over the entire Universe, detecting neutrinos coming through the Earth from the northern skies, as well as from around the southern skies," said Vladimir Papitashvili of the National Science Foundation (NSF) Division of Polar Programs.

In April 2012 IceCube detected two high-energy events above 1 petaelectronvolt (PeV), nicknamed Bert and Ernie, the first astrophysical neutrinos definitively recorded by a terrestrial detector. After Bert and Ernie were discovered, the IceCube team searched their records from May 2010 to May 2012 of events that fell slightly below the energy level of their original search. They discovered 26 more high-energy events, all at levels of 30 teraelectronvolts (TeV) or higher, indicative of astrophysical neutrinos. Preliminary results of this analysis were presented May 15 at the IceCube Particle Astrophysics Symposium at UW-Madison. The analysis presented in Science reveals a highly statistically significant signal (more than 4 sigma), providing solid evidence that IceCube has successfully detected high-energy extraterrestrial neutrinos, said UMD's Sullivan.

Since astrophysical neutrinos move in straight lines unimpeded by outside forces, they can act as pointers to the place in the galaxy where they originated. The 28 events recorded so far are too few to point to any one location, Sullivan said. Over the coming years, the IceCube team will watch, "like waiting for a long exposure photograph," as more measurements fill in a picture that may reveal the point of origin of these intriguing phenomena.

New detection systems for astrophysical neutrinos are also in the works. Hoffman is leading the development of the Askaryan Radio Array, a neutrino telescope that uses radio frequency, which transmits best through very cold ice, to detect the particles. Plans are underway for 37 subsurface clusters of radio antennae

The IceCube Neutrino Observatory was built under a NSF Major Research Equipment and Facilities Construction grant, with assistance from partner funding agencies around the world. The NSF's Division of Polar Programs and Physics Division continue to support the project with a Maintenance and Operations grant, along with international support from participating institutes and their funding agencies.

UMD contributors to the IceCube collaboration include Sullivan and Hoffman; UMD faculty and staff members Erik Blaufuss, John Felde, Henrike Wissing, Alex Olivas, Donald La Dieu, and Torsten Schmidt; and graduate students Elim Cheung, Robert Hellauer, Ryan Maunu, and Michael Richman.

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Infant galaxies merging near ‘cosmic dawn’

Astronomers using the combined power of the Atacama Large Millimeter/submillimeter Array (ALMA) telescope and NASA's Hubble Space Telescope have discovered a far-flung trio of primitive galaxies nestled inside an enormous blob of primordial gas nearly ...
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Evidence of jet in Milky Way’s black hole

Nov. 20, 2013 — Astronomers have long sought strong evidence that Sagittarius A* (Sgr A*), the supermassive black hole at the center of the Milky Way, is producing a jet of high-energy particles. Finally they have found it, in new results from NASA's Chandra X-ray Observatory and the National Science Foundation's Very Large Array (VLA) radio telescope.

Previous studies, using a variety of telescopes, suggested there was a jet, but these reports -- including the orientation of the suspected jets -- often contradicted each other and were not considered definitive.

"For decades astronomers have looked for a jet associated with the Milky Way's black hole. Our new observations make the strongest case yet for such a jet," said Zhiyuan Li of Nanjing University in China, lead author of a study appearing in an upcoming edition of The Astrophysical Journal and available online now.

Jets of high-energy particles are found throughout the universe, on large and small scales. They are produced by young stars and by black holes a thousand times larger than the Milky Way's black hole. They play important roles in transporting energy away from the central object and, on a galactic scale, in regulating the rate of formation of new stars.

"We were very eager to find a jet from Sgr A* because it tells us the direction of the black hole's spin axis. This gives us important clues about the growth history of the black hole," said Mark Morris of the University of California at Los Angeles, a co-author of the study.

The study shows the spin axis of Sgr A* is pointing in one direction, parallel to the rotation axis of the Milky Way, which indicates to astronomers that gas and dust have migrated steadily into Sgr A* over the past 10 billion years. If the Milky Way had collided with large galaxies in the recent past and their central black holes had merged with Sgr A*, the jet could point in any direction.

The jet appears to be running into gas near Sgr A*, producing X-rays detected by Chandra and radio emission observed by the VLA. The two key pieces of evidence for the jet are a straight line of X-ray emitting gas that points toward Sgr A* and a shock front -- similar to a sonic boom -- seen in radio data, where the jet appears to be striking the gas. Additionally, the energy signature, or spectrum, in X-rays of Sgr A* resembles that of jets coming from supermassive black holes in other galaxies.

Scientists think jets are produced when some material falling toward the black hole is redirected outward. Since Sgr A* is presently known to be consuming very little material, it is not surprising that the jet appears weak. A jet in the opposite direction is not seen, possibly because of gas or dust blocking the line of sight from Earth or a lack of material to fuel the jet.

The region around Sgr A* is faint, which means the black hole has been quiet in the past few hundred years. However, a separate Chandra study announced last month shows that it was at least a million times brighter before then.

"We know this giant black hole has been much more active at consuming material in the past. When it stirs again, the jet may brighten dramatically," said co-author Frederick K. Baganoff of the Massachusetts Institute of Technology in Cambridge, Mass.

Astronomers have suggested the giant bubbles of high-energy particles extending out from the Milky Way and detected by NASA's Fermi Gamma Ray Telescope in 2008 are caused by jets from Sgr A* that are aligned with the rotation axis of the galaxy. The latest results from Chandra support this explanation.

The supermassive black hole at the center of the Milky Way is about four million times more massive than our Sun and lies about 26,000 light-years from Earth. The Chandra observations in this study were taken between September 1999 and March 2011, with a total exposure of about 17 days.

NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra Program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

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Impacts of plant invasions become less robust over time: Invasive plants are more likely to be replaced by other ‘invasives’

Nov. 20, 2013 — Among the most impressive ecological findings of the past 25 years is the ability of invasive plants to radically change ecosystem function. Yet few if any studies have examined whether ecosystem impacts of invasions persist over time, and what that means for plant communities and ecosystem restoration.

UC Santa Barbara's Carla D'Antonio, Schuyler Professor of Environmental Studies, has conducted one of the only long-term studies of plant invader impacts that spans two decades. Returning to the same grass-invaded field sites in Hawaii Volcanoes National Park that she used in her 1990-1995 studies, D'Antonio, along with postdoctoral scholar Stephanie Yelenik, gathered new data that shed light on mechanisms regulating exotic plant dominance and community change through invasion. The findings are published online today in Nature.

"We were able to take advantage of detailed studies I and others had conducted in the 1990s. We permanently marked sites we had set up and were able to go back and gain insight into how plant invasions changed over time without management," said D'Antonio, who also is a professor in the Department of Ecology, Evolution and Marine Biology. "Such studies are important because managers have little money to control invasive species or to study how impacts might change without management."

"Non-native plants can have very large impacts on ecosystem functioning -- including altering groundwater, soil salinity or pH and pollination syndromes," said lead author Yelenik, who earned her doctorate from UCSB's Department of Ecology, Evolution and Marine Biology and now works for the U.S. Geological Survey's Pacific Island Ecosystems Research Center on the island of Hawaii.

When D'Antonio and Yelenik revisited the study sites, they noticed that the invasive exotic perennial grasses (primarily an African invader called Melinis minutiflora) were dying, so they decided to repeat measures of nutrient cycling and plant community change. They found that the grasses' self-reinforcing effects on soil nutrients had disappeared and the percentage of invader coverage had declined.

Data showed that in the past 17 years, nitrogen mineralization rates at the sites dominated by the exotic grasses declined by half, returning them to pre-invasion levels. Nitrogen mineralization is the process by which organic nitrogen is converted to plant-available inorganic forms.

"Measuring mineralization the way we do is extremely time-consuming and expensive, so we did it in snapshots of time (mid-1990s versus 2010-2012)," Yelenik explained. "This is less than ideal because differences between the two study periods could be due to differences in rainfall."

To eliminate rainfall as a factor, the researchers examined long-term rainfall data for the region to determine if a relationship exists between nitrogen mineralization and rainfall during the study years. The data showed that rainfall during the two study periods was similar. In addition, rainfall did not correlate with differences in mineralization between time points. A mineralization assay in the lab, where moisture was kept constant, showed similar patterns to the researchers' most recent field data, gathered in 2011 and 2012. Taken together, these results suggest that nitrogen mineralization variations between the 1990s and recent years were not due to differences in rainfall.

While the study demonstrates that ecosystem impacts and feedbacks shift over time, it also indicates that this may not necessarily help native species' recovery. Yelenik and D'Antonio conducted a large outplanting experiment to test how a suite of native and exotic woody species responded to shifting ecosystem impacts. They added nitrogen fertilizer to mimic earlier stages of Melinis invasion and reduced Melinis competition to mimic patches during late invasion.

Similar responses occurred in five of the seven outplanted species: Growth rates and survivorship increased due to reduced competition from the exotic grasses as well as nitrogen additions. This indicates that the changing impacts of the grass over time do not alter the seedlings' ability to grow in the ecosystem.

Two nitrogen-fixing trees were exceptions: the native Hawaiian tree Acacia koa and the exotic tree Morella faya (from the Canary Islands but invading Hawaii today). These species did much better in later Melinis invasion conditions, and Morella faya did particularly well.

"The non-native Morella faya did a lot better for various reasons, but primarily because it has a faster growth rate," Yelenik said. "Plus in our sites it is bird-dispersed, which means it gets around and is, in fact, moving into the sites at a frightening rate. By contrast, the native Acacia did reasonably well in the experiment, but it just does not have as robust a growth rate as Morella. It is a very slow disperser and sparse in the region so we are not seeing it entering the sites on its own."

An important lesson here is that even if plant invasions can slow down on their own given enough time, native species may need further assistance in order to make a comeback, the researchers said. Other invaders may be poised to take advantage of reduced competition from the original invader.

"Knowing the mechanisms of how and why invasions alter ecosystems is insightful for predicting what will happen, but without further management we may not get native species back," Yelenik said. "When we see non-native species dying back and getting patchy, that may be the time to plant native species. It might turn out to be the most cost-effective way to get an ecosystem back to a more desirable state."