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  • richardmitnick 3:45 pm on October 2, 2014 Permalink | Reply
    Tags: , , , Brown University,   

    From Brown- “Invasive species: Darwin had it right” 

    Brown University
    Brown University

    October 2, 2014
    David Orenstein 401-863-1862

    Based on insights first articulated by Charles Darwin, professors at Brown University and Syracuse University have developed and tested the “evolutionary imbalance hypothesis [ETH]” to help predict species invasiveness in ecosystems. The results suggest the importance of accounting for the evolutionary histories of the donor and recipient regions in invasions.

    Dov Sax of Brown University and Jason Fridley of Syracuse University aren’t proposing a novel idea to explain species invasiveness. In fact, Charles Darwin articulated it first. What’s new about Sax and Fridley’s “Evolutionary Imbalance Hypothesis” (EIH) is that they’ve tested it using quantifiable evidence and report in Global Ecology and Biogeography that the EIH works well.

    The EIH idea is this: Species from regions with deep and diverse evolutionary histories are more likely to become successful invaders in regions with less deep, less diverse evolutionary histories. To predict the probability of invasiveness, ecologists can quantify the imbalance between the evolutionary histories of “donor” and “recipient” regions as Sax and Fridley demonstrate in several examples.

    dar
    Survival of the fittest: An iceplant, from a region of high diversity in South Africa, is overtopping and killing a native shrub on the New Zealand coast, a region with far less diversity. Plant lines that have had to struggle against robust competition are strong invaders in areas where native plants have had an easier time. Photo: Jason Fridley

    Darwin’s original insight was that the more challenges a region’s species have faced in their evolution, the more robust they’ll be in new environments.

    “As natural selection acts by competition, it adapts the inhabitants of each country only in relation to the degree of perfection of their associates,” Darwin wrote in 1859. Better tested species, such as those from larger regions, he reasoned, have “consequently been advanced through natural selection and competition to a higher stage of perfection or dominating power.”

    To Sax and Fridley the explanatory power of EIH suggests that when analyzing invasiveness, ecologists should add historical evolutionary imbalance to the other factors they consider.

    “Invasion biology is well-studied now, but this is never listed there even though Darwin basically spelled it out,” said Sax, associate of ecology and evolutionary biology. “It certainly hasn’t been tested before. We think this is a really important part of the story.”

    cd
    Charles Darwin

    The theory was correct. What was missing was quantifiable evidence. That evidence has now been collected.

    Evidence for EIH

    Advancing Darwin’s insight from idea to hypothesis required determining a way to test it against measurable evidence. The ideal data would encapsulate a region’s population size and diversity, relative environmental stability and habitat age, and the intensity of competition. Sax and Fridley found a suitable proxy: “phylogenetic diversity (PD)” , an index of how many unique lineages have developed in a region over the time of their evolution.

    “All else equal, our expectation is that biotas represented by lineages of greater number or longer evolutionary history should be more likely to have produced a more optimal solution to a given environmental problem, and it is this regional disparity, approximated by PD, that allows predictions of global invasion patterns,” they wrote.

    With a candidate measure, they put EIH to the test.

    Using detailed databases on plant species in 35 regions of the world, they looked at the relative success of those species’ invasiveness in three well-documented destinations: Eastern North America, the Czech Republic, and New Zealand.

    They found that in all three regions, the higher the PD of a species’ native region, the more likely it was to become invasive in its new home. The size of the effect varied among the three regions, which have different evolutionary histories, but it was statistically clear that plants forged in rough neighborhoods were better able to bully their way into a new region than those from evolutionarily more “naive” areas.

    Sax and Fridley conducted another test of the EIH in animals by looking at cases where marine animals were suddenly able to mix after they became united by canals. The EIH predicts that an imbalance of evolutionary robustness between the sides, would allow a species-rich region to dominate a less diverse one on the other side of the canal by even more than a mere random mixing would suggest.

    The idea has a paleontological precedent. When the Bering land bridge became the Bering Strait, it offered marine mollusks a new polar path between the Atlantic and Pacific Oceans. Previous research has shown that more kinds of mollusks successfully migrated from the diverse Pacific to the less diverse Atlantic than vice-versa, and by more so than by their relative abundance.

    In the new paper, Sax and Fridley examined what has happened since the openings of the Suez Canal in Egypt, the Erie Canal in New York, and the Panama Canal. The vastly greater evolutionary diversity in the Red Sea and Indian Ocean compared to the Mediterranean Sea and the Atlantic led to an overwhelming flow of species north through the Suez.

    But evolutionary imbalances across the Erie and Panama Canals were fairly small (the Panama canal connects freshwater drainages of the Atlantic and Pacific that were much more ecologically similar than the oceans) so as EIH again predicts, there was a more even balance of cross-canal species invasions.

    Applicable predictions

    Sax and Fridley acknowledge in the paper that the EIH does not singlehandedly predict the success of individual species in specific invasions. Instead it allows for ecosystem managers to assess a relative invasiveness risk based on the evolutionary history of their ecosystem and that of other regions. Take, for instance, a wildlife official in a historically isolated ecosystem such as an island.

    “They already know to be worried, but this would suggest they should be more worried about imports from some parts of the world than others,” Sax said.

    Not all invasions are bad, Sax noted. Newcomers can provide some ecosystem services — such as erosion control — more capably if they can become established. The EIH can help in assessments of whether a new wave of potential invasion is likely to change the way an ecosystem will provide its services, for better or worse.

    “It might help to explain why non-natives in some cases might improve ecosystem functioning,” Sax said.

    But perhaps Darwin already knew all that.

    See the full article here.

    Welcome to Brown

    Rhode Island Hall: Rhode Island Hall’s classical exterior was recently renovated with a modern interiorRhode Island Hall: Rhode Island Hall’s classical exterior was recently renovated with a modern interior

    Located in historic Providence, Rhode Island and founded in 1764, Brown University is the seventh-oldest college in the United States. Brown is an independent, coeducational Ivy League institution comprising undergraduate and graduate programs, plus the Alpert Medical School, School of Public Health, School of Engineering, and the School of Professional Studies.

    With its talented and motivated student body and accomplished faculty, Brown is a leading research university that maintains a particular commitment to exceptional undergraduate instruction.

    Brown’s vibrant, diverse community consists of 6,000 undergraduates, 2,000 graduate students, 400 medical school students, more than 5,000 summer, visiting and online students, and nearly 700 faculty members. Brown students come from all 50 states and more than 100 countries.

    Undergraduates pursue bachelor’s degrees in more than 70 concentrations, ranging from Egyptology to cognitive neuroscience. Anything’s possible at Brown—the university’s commitment to undergraduate freedom means students must take responsibility as architects of their courses of study.

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  • richardmitnick 2:25 pm on September 2, 2014 Permalink | Reply
    Tags: , Brown University, Extinctions   

    From Brown: “Extinctions during human era worse than thought” 

    Brown University
    Brown University

    September 2, 2014
    David Orenstein 401-863-1862

    It’s hard to comprehend how bad the current rate of species extinction around the world has become without knowing what it was before people came along. The newest estimate is that the pre-human rate was 10 times lower than scientists had thought, which means that the current level is 10 times worse.

    Extinctions are about 1,000 times more frequent now than in the 60 million years before people came along. The explanation from lead author Jurriaan de Vos, a Brown University postdoctoral researcher, senior author Stuart Pimm, a Duke University professor, and their team appears online in the journal Conservation Biology.

    “This reinforces the urgency to conserve what is left and to try to reduce our impacts,” said de Vos, who began the work while at the University of Zurich. “It was very, very different before humans entered the scene.”

    In absolute, albeit rough, terms the paper calculates a “normal background rate” of extinction of 0.1 extinctions per million species per year. That revises the figure of 1 extinction per million species per year that Pimm estimated in prior work in the 1990s. By contrast, the current extinction rate is more on the order of 100 extinctions per million species per year.

    Orders of magnitude, rather than precise numbers are about the best any method can do for a global extinction rate, de Vos said. “That’s just being honest about the uncertainty there is in these type of analyses.”

    jd
    Jurriaan de Vos
    “This reinforces the urgency to conserve what is left and to try to reduce our impacts. It was very, very different before humans entered the scene.” Photo: David Orenstein/Brown University

    From fossils to genetics

    The new estimate improves markedly on prior ones mostly because it goes beyond the fossil record. Fossils are helpful sources of information, but their shortcomings include disproportionate representation of hard-bodied sea animals and the problem that they often only allow identification of the animal or plant’s genus, but not its exact species.

    What the fossils do show clearly is that apart from a few cataclysms over geological periods — such as the one that eliminated the dinosaurs — biodiversity has slowly increased.

    The new study next examined evidence from the evolutionary family trees — phylogenies — of numerous plant and animal species. Phylogenies, constructed by studying DNA, trace how groups of species have changed over time, adding new genetic lineages and losing unsuccessful ones. They provide rich details of how species have diversified over time.

    “The diversification rate is the speciation rate minus the extinction rate,” said co-author Lucas Joppa, a scientist at Microsoft Research in Redmond, Wash. “The total number of species on earth has not been declining in recent geological history. It is either constant or increasing. Therefore, the average rate at which groups grew in their numbers of species must have been similar to or higher than the rate at which other groups lost species through extinction.”

    The work compiled scores of studies of molecular phylogenies on how fast species diversified.

    For a third approach, de Vos noted that the exponential climb of species diversity should take a steeper upward turn in the current era because the newest species haven’t gone extinct yet.

    “It’s rather like your bank account on the day you get paid,” he said. “It gets a burst of funds — akin to new species — that will quickly become extinct as you pay your bills.”

    By comparing that rise of the number of species from the as-yet unchecked speciation rate with the historical trend (it was “log-linear”) evident in the phylogenies, he could therefore create a predictive model of what the counteracting historical extinction rate must have been.

    The researchers honed their models by testing them with simulated data for which they knew an actual extinction rate. The final models yielded accurate results. They tested the models to see how they performed when certain key assumptions were wrong and on average the models remained correct (in the aggregate, if not always for every species group).

    All three data approaches together yielded a normal background extinction rate squarely in the order of 0.1 extinctions per million species per year.

    A human role

    There is little doubt among the scientists that humans are not merely witnesses to the current elevated extinction rate. This paper follows a recent one in Science , authored by Pimm, Joppa, and other colleagues, that tracks where species are threatened or confined to small ranges around the globe. In most cases, the main cause of extinctions is human population growth and per capita consumption, although the paper also notes how humans have been able to promote conservation.

    The new study, Pimm said, emphasizes that the current extinction rate is a more severe crisis than previously understood.

    “We’ve known for 20 years that current rates of species extinctions are exceptionally high,” said Pimm, president of the conservation nonprofit organization SavingSpecies. “This new study comes up with a better estimate of the normal background rate — how fast species would go extinct were it not for human actions. It’s lower than we thought, meaning that the current extinction crisis is much worse by comparison.”

    Other authors on the paper are John Gittleman and Patrick Stephens of the University of Georgia.

    See the full article here.

    Welcome to Brown

    Rhode Island Hall: Rhode Island Hall’s classical exterior was recently renovated with a modern interiorRhode Island Hall: Rhode Island Hall’s classical exterior was recently renovated with a modern interior

    Located in historic Providence, Rhode Island and founded in 1764, Brown University is the seventh-oldest college in the United States. Brown is an independent, coeducational Ivy League institution comprising undergraduate and graduate programs, plus the Alpert Medical School, School of Public Health, School of Engineering, and the School of Professional Studies.

    With its talented and motivated student body and accomplished faculty, Brown is a leading research university that maintains a particular commitment to exceptional undergraduate instruction.

    Brown’s vibrant, diverse community consists of 6,000 undergraduates, 2,000 graduate students, 400 medical school students, more than 5,000 summer, visiting and online students, and nearly 700 faculty members. Brown students come from all 50 states and more than 100 countries.

    Undergraduates pursue bachelor’s degrees in more than 70 concentrations, ranging from Egyptology to cognitive neuroscience. Anything’s possible at Brown—the university’s commitment to undergraduate freedom means students must take responsibility as architects of their courses of study.

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  • richardmitnick 11:05 am on August 19, 2014 Permalink | Reply
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    From Brown: “Intimacy a strong motivator for PrEP HIV prevention” 

    Brown University
    Brown University

    August 19, 2014
    David Orenstein

    Men in steady same-sex relationships where both partners are HIV negative will often forgo condoms out of a desire to preserve intimacy, even if they also have sex outside the relationship. But the risk of HIV still lurks. In a new study of gay and bisexual men who reported at least one instance of condomless anal sex in the last 30 days, researchers found that the same desire for intimacy is also a strong predictor of whether men would be willing to take antiretroviral medications to prevent HIV, an emerging practice known as pre-exposure prophylaxis or PrEP.

    Earlier this year the U.S. Public Health Service recommended that people at high risk of getting HIV use PrEP, including gay or bisexual men who have condomless anal sex. But as the recommendation becomes clinical practice, many people are wondering whether men will make PrEP part of their daily lives and what will keep them motivated to adhere to it strictly, which is required if the medication is to have its protective effect.

    The new study, published in the Annals of Behavioral Medicine, suggests that PrEP’s appeal to many men who have sex with men (MSM) in romantic relationships with HIV-negative partners is the perception that it can allow them to remain intimate with their partners while still having some protection from HIV.

    kg
    Kristi Gamarel
    “Sex doesn’t happen in a vacuum — interpersonal and relationship context really matter.”

    “In this sample of men who are in a relationship with a perceived HIV-negative man, we found that intimacy motivation was the strongest predictor [of adopting PrEP],” said Kristi Gamarel, a psychiatry and human behavior postdoctoral researcher in the Warren Alpert Medical School of Brown University. She was at the City University of New York with senior author and principal investigator for the NIH-funded project, Sarit Golub, when she performed the research. “Sex doesn’t happen in a vacuum — interpersonal and relationship context really matter. Many HIV infections are occurring between people who are in a primary relationship.”

    The study is based on extensive interviews with 164 HIV-negative MSMs who were in steady same-sex relationships and who had condomless anal sex at least once in the prior 30 days. The researchers found in a multivariate statistical analysis that those who rated intimacy highly as a reason why they sometimes engage in condomless sex also were 55 percent more likely to say they would adopt PrEP if it were available for free (likely a hypothetical condition for many, but not necessarily all, recipients).

    In basic analyses reported in the paper, there were several other factors in the study that also predicted a greater likelihood of adopting PrEP: older age, higher perception of HIV risk, sex (either protected or not) with partners outside the main relationship, and having less than a bachelor’s degree level of education. But upon controlling for possible overlap among factors, desire for intimacy, low education levels and to a lesser extent older age survived as the strongest predictors of using PrEP.

    Relationships matter

    An important implication of the study’s findings are that as physicians and counselors discuss PrEP with MSM in steady relationships, Gamarel said, they should consider that a desire for intimacy in the relationship appears to be a prime motivation.

    “For people who are disseminating PrEP or talking to patients about PrEP, I think it’s important to think about their relationships,” Gamarel said. “Something that’s being supported and endorsed right now by the World Health Organization is couples voluntary testing and counseling. That may be a way to disseminate PrEP and to allow couples to have a discussion about whether PrEP is good for their relationship and how they can support each other using PrEP.”

    Gamarel cautioned that the study results cannot be taken as evidence that PrEP will reduce condom use. The men in this study were already forgoing condoms at times without being on PrEP, Gamarel notes. The study simply sought to ascertain whether these men would adopt PrEP and to determine why. Condoms remain uniquely important to gay men’s sexual health, she noted, both because they reduce the risk of HIV transmission and because they can block other sexually transmitted infections that PrEP does not.

    The National Institute of Mental Health funded the study (grant: R01MH095565 to Golub).

    See the full article here.

    Welcome to Brown

    Rhode Island Hall: Rhode Island Hall’s classical exterior was recently renovated with a modern interiorRhode Island Hall: Rhode Island Hall’s classical exterior was recently renovated with a modern interior

    Located in historic Providence, Rhode Island and founded in 1764, Brown University is the seventh-oldest college in the United States. Brown is an independent, coeducational Ivy League institution comprising undergraduate and graduate programs, plus the Alpert Medical School, School of Public Health, School of Engineering, and the School of Professional Studies.

    With its talented and motivated student body and accomplished faculty, Brown is a leading research university that maintains a particular commitment to exceptional undergraduate instruction.

    Brown’s vibrant, diverse community consists of 6,000 undergraduates, 2,000 graduate students, 400 medical school students, more than 5,000 summer, visiting and online students, and nearly 700 faculty members. Brown students come from all 50 states and more than 100 countries.

    Undergraduates pursue bachelor’s degrees in more than 70 concentrations, ranging from Egyptology to cognitive neuroscience. Anything’s possible at Brown—the university’s commitment to undergraduate freedom means students must take responsibility as architects of their courses of study.

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  • richardmitnick 8:59 am on July 14, 2014 Permalink | Reply
    Tags: , Brown University, ,   

    From Brown: “Researchers discover boron ‘buckyball'” 

    Brown University
    Brown University

    July 9, 2014
    Kevin Stacey

    The discovery 30 years ago of soccer-ball-shaped carbon molecules called buckyballs helped to spur an explosion of nanotechnology research. Now, there appears to be a new ball on the pitch.

    Buckyball
    Typical buckyball configuration

    Researchers from Brown University, Shanxi University and Tsinghua University in China have shown that a cluster of 40 boron atoms forms a hollow molecular cage similar to a carbon buckyball. It’s the first experimental evidence that a boron cage structure — previously only a matter of speculation — does indeed exist.

    “This is the first time that a boron cage has been observed experimentally,” said Lai-Sheng Wang, a professor of chemistry at Brown who led the team that made the discovery. “As a chemist, finding new molecules and structures is always exciting. The fact that boron has the capacity to form this kind of structure is very interesting.”

    Wang and his colleagues describe the molecule, which they’ve dubbed borospherene, in the journal Nature Chemistry.

    Carbon buckyballs are made of 60 carbon atoms arranged in pentagons and hexagons to form a sphere — like a soccer ball. Their discovery in 1985 was soon followed by discoveries of other hollow carbon structures including carbon nanotubes. Another famous carbon nanomaterial — a one-atom-thick sheet called graphene — followed shortly after.

    Graphene sheet
    The carbon buckyball has a boron cousin. A cluster for 40 boron atoms forms a hollow cage-like molecule.

    After buckyballs, scientists wondered if other elements might form these odd hollow structures. One candidate was boron, carbon’s neighbor on the periodic table. But because boron has one less electron than carbon, it can’t form the same 60-atom structure found in the buckyball. The missing electrons would cause the cluster to collapse on itself. If a boron cage existed, it would have to have a different number of atoms.

    Wang and his research group have been studying boron chemistry for years. In a paper published earlier this year, Wang and his colleagues showed that clusters of 36 boron atoms form one-atom-thick disks, which might be stitched together to form an analog to graphene, dubbed borophene. Wang’s preliminary work suggested that there was also something special about boron clusters with 40 atoms. They seemed to be abnormally stable compared to other boron clusters.

    Figuring out what that 40-atom cluster actually looks like required a combination of experimental work and modeling using high-powered supercomputers.

    On the computer, Wang’s colleagues modeled over 10,000 possible arrangements of 40 boron atoms bonded to each other. The computer simulations estimate not only the shapes of the structures, but also estimate the electron binding energy for each structure — a measure of how tightly a molecule holds its electrons. The spectrum of binding energies serves as a unique fingerprint of each potential structure.

    The next step is to test the actual binding energies of boron clusters in the lab to see if they match any of the theoretical structures generated by the computer. To do that, Wang and his colleagues used a technique called photoelectron spectroscopy.

    Chunks of bulk boron are zapped with a laser to create vapor of boron atoms. A jet of helium then freezes the vapor into tiny clusters of atoms. The clusters of 40 atoms were isolated by weight then zapped with a second laser, which knocks an electron out of the cluster. The ejected electron flies down a long tube Wang calls his “electron racetrack.” The speed at which the electrons fly down the racetrack is used to determine the cluster’s electron binding energy spectrum — its structural fingerprint.

    The experiments showed that 40-atom-clusters form two structures with distinct binding spectra. Those spectra turned out to be a dead-on match with the spectra for two structures generated by the computer models. One was a semi-flat molecule and the other was the buckyball-like spherical cage.

    “The experimental sighting of a binding spectrum that matched our models was of paramount importance,” Wang said. “The experiment gives us these very specific signatures, and those signatures fit our models.”

    The borospherene molecule isn’t quite as spherical as its carbon cousin. Rather than a series of five- and six-membered rings formed by carbon, borospherene consists of 48 triangles, four seven-sided rings and two six-membered rings. Several atoms stick out a bit from the others, making the surface of borospherene somewhat less smooth than a buckyball.

    As for possible uses for borospherene, it’s a little too early to tell, Wang says. One possibility, he points out, could be hydrogen storage. Because of the electron deficiency of boron, borospherene would likely bond well with hydrogen. So tiny boron cages could serve as safe houses for hydrogen molecules.

    But for now, Wang is enjoying the discovery.

    “For us, just to be the first to have observed this, that’s a pretty big deal,” Wang said. “Of course if it turns out to be useful that would be great, but we don’t know yet. Hopefully this initial finding will stimulate further interest in boron clusters and new ideas to synthesize them in bulk quantities.”

    The theoretical modeling was done with a group led by Prof. Si-Dian Li from Shanxi University and a group led by Prof. Jun Li from Tsinghua University. The work was supported by the U.S. National Science Foundation (CHE-1263745) and the National Natural Science Foundation of China.

    See the full article here.

    Welcome to Brown

    Rhode Island Hall: Rhode Island Hall’s classical exterior was recently renovated with a modern interiorRhode Island Hall: Rhode Island Hall’s classical exterior was recently renovated with a modern interior

    Located in historic Providence, Rhode Island and founded in 1764, Brown University is the seventh-oldest college in the United States. Brown is an independent, coeducational Ivy League institution comprising undergraduate and graduate programs, plus the Alpert Medical School, School of Public Health, School of Engineering, and the School of Professional Studies.

    With its talented and motivated student body and accomplished faculty, Brown is a leading research university that maintains a particular commitment to exceptional undergraduate instruction.

    Brown’s vibrant, diverse community consists of 6,000 undergraduates, 2,000 graduate students, 400 medical school students, more than 5,000 summer, visiting and online students, and nearly 700 faculty members. Brown students come from all 50 states and more than 100 countries.

    Undergraduates pursue bachelor’s degrees in more than 70 concentrations, ranging from Egyptology to cognitive neuroscience. Anything’s possible at Brown—the university’s commitment to undergraduate freedom means students must take responsibility as architects of their courses of study.


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  • richardmitnick 5:44 am on July 3, 2014 Permalink | Reply
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    From Brown: “Stem cell type resists chemo drug” 

    Brown University
    Brown University

    July 2, 2014
    David Orenstein 401-863-1862

    In lab tests, Brown University researchers have found that adipose-derived stem cells, which can generate bone tissue, appear resistant to the toxicity of the chemotherapy drug methotrexate, which degrades bone in patients such as kids suffering from acute lymphoblastic leukemia. The newly published findings are preliminary but more tests are planned.

    A new study shows that adipose-derived human stem cells, which can become vital tissues such as bone, may be highly resistant to the common chemotherapy drug methotrexate (MTX). The preliminary finding from lab testing may prove significant because MTX causes bone tissue damage in many patients.

    MTX is used to treat cancers including acute lymphoblastic leukemia, the most common form of childhood cancer. A major side effect of the therapy, however, is a loss of bone mineral density. Other bone building stem cells, such as bone marrow derived stem cells, have not withstood MTX doses well.

    “Kids undergo chemotherapy at such an important time when they should be growing, but instead they are introduced to this very harsh environment where bone cells are damaged with these drugs,” said Olivia Beane, a Brown University graduate student in the Center for Biomedical Engineering and lead author of the study. “That leads to major long-term side effects including osteoporosis and bone defects. If we found a stem cell that was resistant to the chemotherapeutic agent and could promote bone growth by becoming bone itself, then maybe they wouldn’t have these issues.”

    Stem cell survivors

    Originally Beane was doing much more basic research. She was looking for chemicals that could help purify adipose-derived stem cells (ASCs) from mixed cell cultures to encourage their proliferation. Among other things, she she tried chemotherapy drugs, figuring that maybe the ASCs would withstand a drug that other cells could not. The idea that this could help cancer patients did not come until later.

    In the study published online in the journal Experimental Cell Research, Beane exposed pure human ASC cultures, “stromal vascular fraction” (SVF) tissue samples (which include several cell types including ASCs), and cultures of human fibroblast cells, to medically relevant concentrations of chemotherapy drugs for 24 hours. Then she measured how those cell populations fared over the next 10 days. She also measured the ability of MTX-exposed ASCs, both alone and in SVF, to proliferate and turn into other tissues.

    Beane worked with co-authors fellow center member Eric Darling, the Manning Assistant Professor in the Department of Molecular Pharmacology, Physiology and Biotechnology, and research assistant Vera Fonseca.

    They observed that three chemotherapy drugs — cytarabine, etoposide, and vincristine — decimated all three groups of cells, but in contrast to the fibroblast controls, the ASCs withstood a variety of doses of MTX exceptionally well (they resisted vincristine somewhat, too). MTX had little or no effect on ASC viability, cell division, senescence, or their ability to become bone, fat, or cartilage tissue when induced to do so.

    The SVF tissue samples also withstood MTX doses well. That turns out to be significant, Darling said, because that’s the kind of tissue that would actually be clinically useful if an ASC-based therapy were ever developed for cancer patients. Hypothetically, fresh SVF could be harvested from the fat of a donor, as it was for the study, and injected into bone tissue, delivering ASCs to the site.

    To understand why the ASCs resist MTX, the researchers conducted further tests. MTX shuts down DNA biosynthesis by binding the protein dihydrofolate reductase so that it is unavailable to assist in that essential task. The testing showed that ASCs ramped up dihydrofolate reductase levels upon exposure to the drug, meaning they produced enough to overcome a clinically relevant dose of MTX.

    Toward a therapy?

    Now that the researchers are aware of ASC’s ability to resist MTX, they are eager to see if they can make progress toward delivering a medical benefit for cancer patients. They plan several more experiments.

    One is to test ASC survival and performance after 48- and 72-hour exposures to MTX. Another is to begin examining how the cells fare in mouse models of chemotherapy. They also plan to directly compare ASCs and bone marrow-derived stem cells amid various chemotherapies.

    Darling said his team hopes it can make a contribution by helping patients heal from chemotherapy, which does what it must, but at a cost.

    “The first step is to save a life,” he said. “Chemotherapies do a great job of killing cells and killing the cancer, and that’s what you want. But then there is a stage after that where you need to do recovery and regeneration.”

    Further research will reveal whether stem cells can be part of that process.

    The National Institutes of Health (grants R01AR063642, P20GM104937) and the National Science Foundation (CBET1253189) supported the research.

    cells
    Cellular survivor Ten days after treatment with a medically appropriate dose of the chemotherapy drug MTX, adipose-derived stem cells, left, survive while normal human fibroblasts, right, are impaired. Insets show untreated control cells. Darling lab/Brown University

    See the full article here.

    Welcome to Brown

    Rhode Island Hall: Rhode Island Hall’s classical exterior was recently renovated with a modern interiorRhode Island Hall: Rhode Island Hall’s classical exterior was recently renovated with a modern interior

    Located in historic Providence, Rhode Island and founded in 1764, Brown University is the seventh-oldest college in the United States. Brown is an independent, coeducational Ivy League institution comprising undergraduate and graduate programs, plus the Alpert Medical School, School of Public Health, School of Engineering, and the School of Professional Studies.

    With its talented and motivated student body and accomplished faculty, Brown is a leading research university that maintains a particular commitment to exceptional undergraduate instruction.

    Brown’s vibrant, diverse community consists of 6,000 undergraduates, 2,000 graduate students, 400 medical school students, more than 5,000 summer, visiting and online students, and nearly 700 faculty members. Brown students come from all 50 states and more than 100 countries.

    Undergraduates pursue bachelor’s degrees in more than 70 concentrations, ranging from Egyptology to cognitive neuroscience. Anything’s possible at Brown—the university’s commitment to undergraduate freedom means students must take responsibility as architects of their courses of study.


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  • richardmitnick 5:06 am on June 24, 2014 Permalink | Reply
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    From Brown University: “Emergence of bacterial vortex explained” 

    Brown University
    Brown University

    June 20, 2014
    Kevin Stacey

    When a bunch of B. subtilis bacteria are confined within a droplet of water, a very strange thing happens. The chaotic motion of all those individual swimmers spontaneously organizes into a swirling vortex, with bacteria on the outer edge of the droplet moving in one direction while those on the inside move the opposite direction.

    image
    A mysterious vortex in theory and observation Dyes of different colors on the bodies and flagella of bacteria allowed researchers to determine the direction of their swimming. Direct observation confirmed a computer simulation of bacteria swimming in opposite directions within a water drop. Credit: Brown University and Cambridge University

    Researchers from Brown University and the University of Cambridge have explained for the first time how that dual-motion vortex is generated. Using computer modeling and a clever experiment, the researchers show that the fluid flow generated by all those tiny swimmers explains that strange two-way motion.

    The research is published in Proceedings of the National Academy of Sciences.

    Hugo Wioland and and others in the lab of Raymond Goldstein at Cambridge first demonstrated the phenomenon experimentally in 2013. But at that time, the dynamics of the system — especially the two-directional motion — weren’t fully understood. Enkeleida Lushi, now a postdoctoral researcher in Brown’s School of Engineering and an expert in theoretical modeling, started thinking about this problem while at Cambridge on a fellowship last year.

    “These are very simple organisms,” Lushi said. “They do not consciously decide where to go and how to organize. Most of the dynamics occur just due to physical mechanisms, like collisions with each other and the boundary. But there was no intuitive way to explain what was happening with the dual-motion vortex. It was very puzzling.”

    The initial model attempting to reproduce the phenomenon focused on the mechanical interactions between individual bacteria. Those simulations showed that when individuals swimming in random trajectories start bumping into each other in a confined circular space, they tend to orient each other to the same angle relative to the circular boundary. That helps explain how a coordinated motion starts, but can’t explain why individuals toward the outside of the circle move in the opposite direction from those on the inside.

    That part of the phenomenon, it turns out, is a matter of fluid flow.

    “These bacteria are only a few micrometers long,” Lushi said. “At that scale, the fluid flow to them feels very viscous — very different from what we experience in air or even in water. The effect is that any movement that the bacteria make causes disturbances in the flow that will be felt strongly by their neighbors.”

    So Lushi and her colleagues developed a computer simulation, right, that included the fluid flows created when the bacteria swim. B. subtilis swim by turning tiny corkscrew-like appendages called flagella. The flagellar bundle pushes against the fluid, which propels the bacteria forward and pushes the fluid in the opposite direction.

    When Lushi included those dynamics in her simulation, the source of the two-way motion became clear. The bacteria all tend to align themselves facing in the same direction, the simulation showed. But individuals swimming along the outside of the circle created a flow in the fluid in the opposite direction from the direction they’re swimming. Bacteria toward the inside of the circle are forced to swim against that flow, but can’t quite keep up. They end up moving in the same direction as the flow — the opposite direction of the swimmers on the outside.

    To confirm the model, the researchers set up an experiment with real bacteria, right, using colored dyes on the bacterium body and flagella to determine which direction the bacteria were facing. The experiment showed that all the bacteria were indeed attempting to swim in the same direction. But those in the middle were swept backward, apparently by the fluid flow created along the outside. It was just as the model had predicted.

    “It’s a very basic model,” Lushi said, “but in the end it captures this phenomenon very well. It showed that any study of microbes suspended in a liquid should not ignore the motion of that liquid – it could have important repercussions on the microbes.”

    So why study the strange motion of bacteria in a water drop?

    “We want to understand nature where there are many incidences of independent individual units organizing collectively — this bacterial vortex is but one example,” Lushi said. “But also, we might want to eventually control bacterial colonies, for example to limit their spread. The more we understand how they interact and how they move collectively, the better we can devise ways to control their motion.”

    See the full article here.

    Welcome to Brown

    Rhode Island Hall: Rhode Island Hall’s classical exterior was recently renovated with a modern interiorRhode Island Hall: Rhode Island Hall’s classical exterior was recently renovated with a modern interior

    Located in historic Providence, Rhode Island and founded in 1764, Brown University is the seventh-oldest college in the United States. Brown is an independent, coeducational Ivy League institution comprising undergraduate and graduate programs, plus the Alpert Medical School, School of Public Health, School of Engineering, and the School of Professional Studies.

    With its talented and motivated student body and accomplished faculty, Brown is a leading research university that maintains a particular commitment to exceptional undergraduate instruction.

    Brown’s vibrant, diverse community consists of 6,000 undergraduates, 2,000 graduate students, 400 medical school students, more than 5,000 summer, visiting and online students, and nearly 700 faculty members. Brown students come from all 50 states and more than 100 countries.

    Undergraduates pursue bachelor’s degrees in more than 70 concentrations, ranging from Egyptology to cognitive neuroscience. Anything’s possible at Brown—the university’s commitment to undergraduate freedom means students must take responsibility as architects of their courses of study.


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  • richardmitnick 4:23 pm on June 16, 2014 Permalink | Reply
    Tags: , , Brown University,   

    From Brown University: “A virus reveals the physics of nanopores” 

    Brown University
    Brown University

    June 16, 2014
    Media Contact: Kevin Stacey | 401-863-3766

    June 16, 2014 | Media Contact: Kevin Stacey | 401-863-3766

    Nanopores may one day lead a revolution in DNA sequencing. By sliding DNA molecules one at a time through tiny holes in a thin membrane, it may be possible to decode long stretches of DNA at lightning speeds. Scientists, however, haven’t quite figured out the physics of how polymer strands like DNA interact with nanopores. Now, with the help of a particular type of virus, researchers from Brown University have shed new light on this nanoscale physics.

    image2
    A better way to study what actually happens at the nanopore A computer simulation depicts an fd virus translocating through a nanopore. Unlike DNA, which tangles up in solution, the fd remains stiff and straight, allowing researchers to study the physics of translocation through nanopores. Credit: Hendrick de Haan/Stein lab/Brown University

    “What got us interested in this was that everybody in the field studied DNA and developed models for how they interact with nanopores,” said Derek Stein, associate professor of physics and engineering at Brown who directed the research. “But even the most basic things you would hope models would predict starting from the basic properties of DNA — you couldn’t do it. The only way to break out of that rut was to study something different.”

    The findings, published today in Nature Communications, might not only help in the development of nanopore devices for DNA sequencing, they could also lead to a new way of detecting dangerous pathogens.

    Straightening out the physics

    The concept behind nanopore sequencing is fairly simple. A hole just a few billionths of a meter wide is poked in a membrane separating two pools of salty water. An electric current is applied to the system, which occasionally snares a charged DNA strand and whips it through the pore — a phenomenon called translocation. When a molecule translocates, it causes detectable variations in the electric current across the pore. By looking carefully at those variations in current, scientists may be able to distinguish individual nucleotides — the A’s, C’s, G’s and T’s coded in DNA molecules.

    The first commercially available nanopore sequencers may only be a few years away, but despite advances in the field, surprisingly little is known about the basic physics involved when polymers interact with nanopores. That’s partly because of the complexities involved in studying DNA. In solution, DNA molecules form balls of random squiggles, which make understanding their physical behavior extremely difficult.

    For example, the factors governing the speed of DNA translocation aren’t well understood. Sometimes molecules zip through a pore quickly; other times they slither more slowly, and nobody completely understands why.

    image
    A better candidate (atomic force microscope image)The fd virus, stiff and rod-like, helps scientists understand the physics of nanopores. Nanopores could be useful in detecting other viruses that share those characteristics — Ebola and Marburg among them.A better candidate (atomic force microscope image)

    The fd virus, stiff and rod-like, helps scientists understand the physics of nanopores. Nanopores could be useful in detecting other viruses that share those characteristics — Ebola and Marburg among them.One possible explanation is that the squiggly configuration of DNA causes each molecule to experience differences in drag as they’re pulled through the water toward the pore. “If a molecule is crumpled up next to the pore, it has a shorter distance to travel and experiences less drag,” said Angus McMullen, a physics graduate student at Brown and the study’s lead author. “But if it’s stretched out then it would feel drag along the whole length and that would cause it to go slower.”

    The drag effect is impossible to isolate experimentally using DNA, but the virus McMullen and his colleagues studied offered a solution.

    The researchers looked at fd, a harmless virus that infects e. coli bacteria. Two things make the virus an ideal candidate for study with nanpores. First, fd viruses are all identical clones of each other. Second, unlike squiggly DNA, fd virus is a stiff, rod-like molecule. Because the virus doesn’t curl up like DNA does, the effect of drag on each one should be essentially the same every time.

    With drag eliminated as a source of variation in translocation speed, the researchers expected that the only source of variation would be the effect of thermal motion. The tiny virus molecules constantly bump up against the water molecules in which they are immersed. A few random thermal kicks from the rear would speed the virus up as it goes through the pore. A few kicks from the front would slow it down.

    The experiments showed that while thermal motion explained much of the variation in translocation speed, it didn’t explain it all. Much to the researchers’ surprise, they found another source of variation that increased when the voltage across the pore was increased.

    “We thought that the physics would be crystal clear,” said Jay Tang, associate professor of physics and engineering at Brown and one of the study’s co-authors. “You have this stiff [virus] with well-defined diameter and size and you would expect a very clear-cut signal. As it turns out, we found some puzzling physics we can only partially explain ourselves.”

    The researchers can’t say for sure what’s causing the variation they observed, but they have a few ideas.

    “It’s been predicted that depending on where [an object] is inside the pore, it might be pulled harder or weaker,” McMullen said. “If it’s in the center of the pore, it pulls a little bit weaker than if it’s right on the edge. That’s been predicted, but never experimentally verified. This could be evidence of that happening, but we’re still doing follow up work.”

    Toward a nanopore sequencer and more

    A better understanding of translocation speed could improve the accuracy of nanopore sequencing, McMullen says. It would also be helpful in the crucial task of measuring the length of DNA strands. “If you can predict the translocation speed,” McMullen said, “then you can easily get the length of the DNA from how long its translocation was.”

    The research also helped to reveal other aspects of the translocation process that could be useful in designing future devices. The study showed that the electrical current tends to align the viruses head first to the pore, but on occasions when they’re not lined up, they tend to bounce around on the edge of the pore until thermal motion aligns them to go through. However, when the voltage was turned too high, the thermal effects were suppressed and the virus became stuck to the membrane. That suggests a sweet spot in voltage where headfirst translocation is most likely.

    None of this is observable directly — the system is simply too small to be seen in action. But the researchers could infer what was happening by looking at slight changes in the current across the pore.

    “When the viruses miss, they rattle around and we see these little bumps in the current,” Stein said. “So with these little bumps, we’re starting to get an idea of what the molecule is doing before it slides through. Normally these sensors are blind to anything that’s going on until the molecule slides through.”

    That would have been impossible to observe using DNA. The floppiness of the DNA molecule allows it to go through a pore in a folded configuration even if it’s not aligned head-on. But because the virus is stiff, it can’t fold to go through. That enabled the researchers to isolate and observe those contact dynamics.

    “These viruses are unique,” Stein said. “They’re like perfect little yardsticks.”

    In addition to shedding light on basic physics, the work might also have another application. While the fd virus itself is harmless, the bacteria it infects — e. coli — is not. Based on this work, it might be possible to build a nanopore device for detecting the presence of fd, and by proxy, e. coli. Other dangerous viruses — Ebola and Marburg among them — share the same rod-like structure as fd.

    “This might be an easy way to detect these viruses,” Tang said. “So that’s another potential application for this.”

    The work was supported by the National Science Foundation (grants CBET0846505 and PHYS1058375), and the Brown University Institute for Molecular and Nanoscale Innovation. Hendrick W. de Haan, of University of Ontario Institute of Technology, was also an author on the study.

    See the full article here.

    Welcome to Brown

    Rhode Island Hall: Rhode Island Hall’s classical exterior was recently renovated with a modern interiorRhode Island Hall: Rhode Island Hall’s classical exterior was recently renovated with a modern interior

    Located in historic Providence, Rhode Island and founded in 1764, Brown University is the seventh-oldest college in the United States. Brown is an independent, coeducational Ivy League institution comprising undergraduate and graduate programs, plus the Alpert Medical School, School of Public Health, School of Engineering, and the School of Professional Studies.

    With its talented and motivated student body and accomplished faculty, Brown is a leading research university that maintains a particular commitment to exceptional undergraduate instruction.

    Brown’s vibrant, diverse community consists of 6,000 undergraduates, 2,000 graduate students, 400 medical school students, more than 5,000 summer, visiting and online students, and nearly 700 faculty members. Brown students come from all 50 states and more than 100 countries.

    Undergraduates pursue bachelor’s degrees in more than 70 concentrations, ranging from Egyptology to cognitive neuroscience. Anything’s possible at Brown—the university’s commitment to undergraduate freedom means students must take responsibility as architects of their courses of study.


    ScienceSprings is powered by MAINGEAR computers

     
  • richardmitnick 2:29 pm on June 12, 2014 Permalink | Reply
    Tags: , , Brown University, Immunology,   

    From Brown University: “Proliferation cues ‘natural killer’ cells for job change” 

    Brown University
    Brown University

    June 12, 2014
    David Orenstein

    June 12, 2014 | Media Contact: David Orenstein | 401-863-1862

    woman

    Purposeful proliferation Working with colleagues including Professor Christine Biron, graduate student Margarite Tarrio helped discover that when ‘natural killer’ cells proliferate after infection, their role changes from marshaling the immune response to regulating it. Credit: David Orenstein/Brown University

    Why would already abundant ‘natural killer’ cells proliferate even further after subduing an infection? It’s been a biological mystery for 30 years. But now Brown University scientists have an answer: After proliferation, the cells switch from marshaling the immune response to calming it down. The findings illuminate the functions of a critical immune system cell important for early defense against disease induced by viral infection.

    The immune system maintains a rich abundance of “natural killer” cells to confront microbial invaders, but as the body gains the upper hand in various infections it sometimes starts to produce even more of the cells. For three decades, scientists haven’t understood what purpose that serves. In a new paper, Brown University researchers show one: proliferation helps change the NK cells’ function from stimulating the immune response to calming it down, lest it get out of hand.

    In a series of experiments now published online in the Journal of Immunology, the researchers show that the process of proliferation unlocks expression of the gene in NK cells for producing Interleukin-10(IL-10), a protein that moderates other immune system cells.

    “It’s really important for regulating potentially dangerous CD8 T cell responses,” said Margarite Tarrio, co-lead author of the paper and a graduate student in the lab of Brown immunology Professor Christine Biron. “If you get CD8 T cells that are hyperactivated they can cause a tremendous amount of damage.”

    Ever since Biron and colleagues published the first observations of NK cell proliferation in 1982, she has sought to figure out why it happens. Knowing the answer is important both as a matter of basic immunology and because NK cells, as crucial members of the body’s first line of infection defense, are often the subjects of efforts to harness the immune system in protection against infections and cancer.

    “The work provides another important role for lymphocyte proliferation, to set up the conditions needed for changing function,” Biron said. “It is likely to be part of the mechanism for changing the functions of other immune cells, and the insight may help in designing vaccines.”

    Shown down to the gene

    An association between NK cells and IL-10 production doesn’t necessarily emerge in all infections, but it does come up in some pretty important ones. Scientists have observed it in human cases of hepatitis C, for example.

    In the new study, the researchers used a different virus, known as MCMV in mice, as part of their investigation of NK proliferation. The human version, CMV, can cause birth defects (http://www.cdc.gov/CMV/index.html) if it’s active in a woman who is pregnant.

    The first step was to confirm that in mice infected with MCMV, NK cells were indeed pumping out the IL-10. The researchers noticed that in highly infected mice, NK cells produced IL-10 about 3.5 days into the infection – days later than when they’d produce IFN-gamma, a protein that helps to mount, rather than defuse, the immune system response.

    In lab cultures, they found that only cells that were about 3.5 days post infection would produce IL-10. A subsequent experiment showed that exposure to a virus wasn’t necessary, per se, but several rounds of replication and proliferation (over about 3 days) enabled the IL-10 production.

    “Taken together, these studies show that the NK cell IL-10 response is associated with extensive proliferation, either under in vitro conditions independent of infection, or in vivo during infection,” wrote the authors, including co-lead author and former Brown postdoctoral researcher Seung-Hwan Lee, who is now at the University of Ottawa.

    Having shown that IL-10 production was associated with NK cell proliferation, Tarrio, Biron and colleagues sought even more evidence: The mechanism in the NK cells that triggers the switch to IL-10 production.

    They found it by comparing the genome-wide conformation of DNA in NK cells before and after proliferation in infected mice. They found that in NK cells that hadn’t undergone the proliferation process, the gene for IL-10 was tightly wrapped up and inaccessible for expression. Post-proliferation cells had IL-10 genes that were more open and accessible for expression.

    “When we got those results everybody was really excited about it, because pulling out epigenetic changes from a cell population during an infection in vivo is really pretty remarkable,” Tarrio said.

    New investigations

    Because the epigenetic study looked at the broader genome of NK cell DNA, not just at the IL-10 gene, Tarrio added, the researchers can now go back to the data to look for other proliferation-induced changes. That could tell them whether proliferation perhaps alters other important functions in NK cells.

    “It’s entirely likely there are other changes going on and it could be for other purposes,” Tarrio said. “This is one answer to why NK cells proliferate.”

    With her first grad school paper now published, Tarrio is continuing the research with Biron. The next question in her thesis work will be how long post-infection proliferation and any associated functional changes persist in the NK cells.

    In addition to Tarrio, Biron and Lee, other authors are Maria Fragoso of Brown and Hong-Wei Sun, Yuka Kanno and John J. O’Shea of the National Institutes of Health.

    The U.S. National Institutes of Health and the Department of Education funded the study.

    See the full article here.

    Welcome to Brown

    Rhode Island Hall: Rhode Island Hall’s classical exterior was recently renovated with a modern interiorRhode Island Hall: Rhode Island Hall’s classical exterior was recently renovated with a modern interior

    Located in historic Providence, Rhode Island and founded in 1764, Brown University is the seventh-oldest college in the United States. Brown is an independent, coeducational Ivy League institution comprising undergraduate and graduate programs, plus the Alpert Medical School, School of Public Health, School of Engineering, and the School of Professional Studies.

    With its talented and motivated student body and accomplished faculty, Brown is a leading research university that maintains a particular commitment to exceptional undergraduate instruction.

    Brown’s vibrant, diverse community consists of 6,000 undergraduates, 2,000 graduate students, 400 medical school students, more than 5,000 summer, visiting and online students, and nearly 700 faculty members. Brown students come from all 50 states and more than 100 countries.

    Undergraduates pursue bachelor’s degrees in more than 70 concentrations, ranging from Egyptology to cognitive neuroscience. Anything’s possible at Brown—the university’s commitment to undergraduate freedom means students must take responsibility as architects of their courses of study.


    ScienceSprings is powered by MAINGEAR computers

     
  • richardmitnick 6:19 pm on May 29, 2014 Permalink | Reply
    Tags: , , , Brown University,   

    From Brown University: “A habitable environment on Martian volcano?” 

    Brown University
    Brown University

    May 27, 2014
    Kevin Stacey | 401-863-3766

    plain
    Possibly habitable environs – Braided fluvial channels (inset) emerge from the edge of glacial deposits roughly 210 million years old on the martian volcano Arsia Mons, nearly twice as high as Mount Everest. (Colors indicate elevation.)

    Credit: NASA/Goddard Space Flight Center/Arizona State University/Brown University

    Heat from a volcano erupting beneath an immense glacier would have created large lakes of liquid water on Mars in the relatively recent past. And where there’s water, there is also the possibility of life. A recent paper by Brown University researchers calculates how much water may have been present near the Arsia Mons volcano and how long it may have remained.

    PROVIDENCE, R.I. [Brown University] — The slopes of a giant Martian volcano, once covered in glacial ice, may have been home to one of the most recent habitable environments yet found on the Red Planet, according to new research led by Brown University geologists.

    Nearly twice as tall as Mount Everest, Arsia Mons is the third tallest volcano on Mars and one of the largest mountains in the solar system. This new analysis of the landforms surrounding Arsia Mons shows that eruptions along the volcano’s northwest flank happened at the same time that a glacier covered the region around 210 million years ago. The heat from those eruptions would have melted massive amounts of ice to form englacial lakes — bodies of water that form within glaciers like liquid bubbles in a half-frozen ice cube.

    The ice-covered lakes of Arsia Mons would have held hundreds of cubic kilometers of meltwater, according to calculations by Kat Scanlon, a graduate student at Brown who led the work. And where there’s water, there’s the possibility of a habitable environment.

    “This is interesting because it’s a way to get a lot of liquid water very recently on Mars,” Scanlon said.

    While 210 million years ago might not sound terribly recent, the Arsia Mons site is much younger than the habitable environments turned up by Curiosity and other Mars rovers. Those sites are all likely older than 2.5 billion years. The fact that the Arsia Mons site is relatively young makes it an interesting target for possible future exploration.

    “If signs of past life are ever found at those older sites, then Arsia Mons would be the next place I would want to go,” Scanlon said.

    A paper describing Scanlon’s work is published in the journal Icarus.

    Scientists have speculated since the 1970s that the northwest flank of Arsia Mons may once have been covered by glacial ice. That view got a big boost in 2003 when Brown geologist Jim Head and Boston University’s David Marchant showed that terrain around Arsia Mons looks strikingly similar to landforms left by receding glaciers in the Dry Valleys of Antarctica. Parallel ridges toward the bottom of the mountain appear to be drop moraines — piles of rubble deposited at the edges of a receding glacier. An assemblage of small hills in the region also appears to be debris left behind by slowly flowing glacial ice.

    The glacier idea got another boost with recently developed climate models for Mars that take into account changes in the planet’s axis tilt. The models suggested that during periods of increased tilt, ice now found at the poles would have migrated toward the equator. That would make Mars’s giant mid-latitude mountains — Ascraeus Mons, Pavonis Mons and Arsia Mons — prime locations for glaciation around 210 million years ago.

    Fire and ice

    Working with Head, Marchant, and Lionel Wilson from the Lancaster Environmental Centre in the U.K., Scanlon looked for evidence that hot volcanic lava may have flowed in the region the same time that the glacier was present. She found plenty.

    Using data from NASA’s Mars Reconnaissance Orbiter, Scanlon found pillow lava formations, similar to those that form on Earth when lava erupts at the bottom of an ocean. She also found the kinds of ridges and mounds that form on Earth when a lava flow is constrained by glacial ice. The pressure of the ice sheet constrains the lava flow, and glacial meltwater chills the erupting lava into fragments of volcanic glass, forming mounds and ridges with steep sides and flat tops. The analysis also turned up evidence of a river formed in a jökulhlaup, a massive flood that occurs when water trapped in a glacier breaks free.

    Based on the sizes of the formations, Scanlon could estimate how much lava would have interacted with the glacier. Using basic thermodynamics, she could then calculate how much meltwater that lava would produce. She found that two of the deposits would have created lakes containing around 40 cubic kilometers of water each. That’s almost a third of the volume of Lake Tahoe in each lake. Another of the formations would have created around 20 cubic kilometers of water.

    Even in the frigid conditions of Mars, that much ice-covered water would have remained liquid for a substantial period of time. Scanlon’s back-of-the-envelope calculation suggests the lakes could have persisted or hundreds or even a few thousand years.

    That may have been long enough for the lakes to be colonized by microbial life forms, if in fact such creatures ever inhabited Mars.

    “There’s been a lot of work on Earth — though not as much as we would like — on the types of microbes that live in these englacial lakes,” Scanlon said. “They’ve been studied mainly as an analog to [Jupiter’s moon] Europa, where you’ve got an entire planet that’s an ice covered lake.”

    In light of this research, it seems possible that those same kinds of environs existed on Mars at this site in the relatively recent past.

    There’s also possibility, Head points out, that some of that glacial ice may still be there. “Remnant craters and ridges strongly suggest that some of the glacial ice remains buried below rock and soil debris,” he said. “That’s interesting from a scientific point of view because it likely preserves in tiny bubbles a record of the atmosphere of Mars hundreds of millions of years ago. But an existing ice deposit might also be an exploitable water source for future human exploration.”

    See the full article here.

    Welcome to Brown

    Rhode Island Hall: Rhode Island Hall’s classical exterior was recently renovated with a modern interiorRhode Island Hall: Rhode Island Hall’s classical exterior was recently renovated with a modern interior

    Located in historic Providence, Rhode Island and founded in 1764, Brown University is the seventh-oldest college in the United States. Brown is an independent, coeducational Ivy League institution comprising undergraduate and graduate programs, plus the Alpert Medical School, School of Public Health, School of Engineering, and the School of Professional Studies.

    With its talented and motivated student body and accomplished faculty, Brown is a leading research university that maintains a particular commitment to exceptional undergraduate instruction.

    Brown’s vibrant, diverse community consists of 6,000 undergraduates, 2,000 graduate students, 400 medical school students, more than 5,000 summer, visiting and online students, and nearly 700 faculty members. Brown students come from all 50 states and more than 100 countries.

    Undergraduates pursue bachelor’s degrees in more than 70 concentrations, ranging from Egyptology to cognitive neuroscience. Anything’s possible at Brown—the university’s commitment to undergraduate freedom means students must take responsibility as architects of their courses of study.


    ScienceSprings is powered by MAINGEAR computers

     
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