Clock this: Dandelion Seeds Have a Vortex Floating Above Their Filaments

     "Dandelion seeds fly using a method that researchers thought would not work in the real world, according to a study published on October 17, 2018, in Nature." Here is a dandelion head, also called a dandelion clock:

     "When some animals, airplanes, or seeds fly, rings of circulating air called vortices form in contact with their wings or wing-like surfaces. These vortices can help to maintain the forces that lift the animal, machine, or seed into the air. 

     Researchers thought that an unattached vortex would be too unstable to persist in nature. Yet the light, puffy seeds of dandelions use vortices that materialize just above their surfaces and lift the seed into the air.

     Dandelion seeds bear filaments that radiate out from a central stalk like the spokes on a bicycle wheel, a feature that seems to be the key to their flight. Many insects harbor such filter-like structures on their wings or legs, suggesting that the use of detached vortices for flight or swimming might be relatively common, says study co-author Dr. Naomi Nakayama, a plant scientist at the U. of Edinburgh.

      As far as vortex rings go, the dandelion's is unusual. Normally, such air bubbles stay attached to an object or totally separate and disappear. But the dandelion’s bubble separates and hangs out above the seed. “When you show it to a fluid dynamicist, it blows their mind,” says study coauthor Dr. Cathal Cummins.

     Researchers were curious about how these bristly seeds of the pappus (the seed plus the filaments) stayed in the air because they looked so different from the wing-like seeds of other plants, such as maple trees. Those structures act like the wings of a bird or airplane, generating pressure differences above and below the wing to fly. To find the answer, Dr. Nakayama and her colleagues put dandelion seeds in a vertical wind tunnel and used a laser to illuminate particles that helped to visualize the airflow around the seed.

     That’s when they saw the vortex floating above the seeds. The amount of open space between the spokes of the seeds seems to be the key to the stability of these detached vortices, says Dr. Cummins. Pressure differences between the air moving through the spokes and the air moving around the seed creates the vortex ring.

     Previous studies have found that dandelion seeds always have between 90 and 110 bristles, says Nakayama. She described it as “extremely consistent”, and that consistency turns out to be very important.

     When the team designed small silicon discs to imitate these spokes, they produced models with a range of openings: from solid discs to ones that were 92% air, like the structures on the dandelion seeds. When the researchers tested these model seeds in their wind tunnel, they found that only the discs that best approximated dandelion seeds could maintain the detached vortex.

     If the number of openings in the discs was even 10% off of those in dandelion seeds, the vortex destabilized. The seed looks inefficient for flight because it has so much open space, says Dr. Nakayama, but these openings are what allow the unattached vortex ring to remain stable."

     “It’s great to see an analysis of something we see every day but didn’t fully understand,” says Dr. Richard Bomphrey, a comparative biomechanist at the Royal Veterinary College. “To discover that there were aerodynamic mechanisms that we didn’t already know — despite the fact that we can fly things at Mach 9 — is always exciting.”

        Wow, hanging vortices in a common flower. Nature sure is dandy!
Steph

Zoë had her Peace Corps gong out service, hitting the gong thrice to represent three years of service. Proud of her and looking ahead to what she'll do next!

“Permafrost” and Thermokarst

     As temperatures rise in the arctic, “permafrost,” permanently frozen ground, is defrosting at an increased rate. 

     "However, permafrost isn't the only thing in the arctic that is disappearing. Exposed rock that was once covered in ice is dissolving, eaten away by acid. The effects of this acid bath could have far-reaching impacts on global climate, according to a new study.

     Icy permafrost is rich in minerals, which are released when the ice melts. The minerals then become vulnerable to chemical weathering, or the breakdown of rock through chemical reactions. Scientists investigated areas once covered by permafrost in the western Canadian arctic, finding evidence of weathering caused by sulfuric acid produced by sulfide minerals that were released when the permafrost melted.

     Another type of naturally occurring chemical erosion is caused by carbonic acid, and it also dissolves rock. But although carbonic-acid weathering locks carbon dioxide (CO2) in place, sulfuric-acid erosion releases CO2 into the atmosphere, and it does so in quantities that were not previously accounted for, researchers described.

      Dramatic changes are underway in the Arctic, which is warming about twice as fast as any other location on earth. Sea ice is rapidly dwindling, which reduces the ocean's heat-reflecting cover, accelerating the rise of ocean temperatures. And polar bears, which depend on sea-ice cover to hunt for seals, are losing their hunting grounds, and have a harder time finding enough to eat. 

     On land, melting permafrost is shaping new landscapes, through a process called thermokarst — a term for thawing-driven erosion that originated in Russia, according to the U.S. Geological Survey (USGS).

     Thermokarst creates land formations such as lakes, pits, and sinkholes. It was not previously known how this process could affect weathering of exposed minerals, and how that might then impact CO2 release, according to the study.

     "These processes may influence the permafrost carbon-climate feedback, but have received little attention," the researchers reported.

     Over geologic time, weathering caused by carbonic acid can help to regulate climate, by trapping CO2 and restricting its transfer into the atmosphere. But the researchers found that thermokarst in regions that were rich in sulfides drove production of sulfuric acid, rather than carbonic acid, and thereby released quantities of CO2."

      These preliminary findings were published online 9/6/18 in the journal Geophysical Research Letters. (The "Plain Language" Abstract is something I've not seen before in professional journals; have you?)

       Thermokarst--easy enough for even kindergartners to understand, eh?
Steph










 


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Forty-four More Planets Beyond Our Own Solar System: Four Have a Year of Less Than 24 Hours

    In research published today, forty-four planets outside our solar system have been unveiled at once,  dwarfing (pun intended) the usual number of confirmations from extrasolar surveys, which is typically a dozen or less. The findings may improve models of solar systems and may help researchers investigate exoplanet atmospheres. Novel techniques developed to validate the findings could hugely accelerate the confirmation of more extrasolar planet candidates.       

     Shown above are the 44 confirmed planets and their approximate size class, orbits, and surface temperatures.
(Image Credit: John Livingston).   

     The 44 validated planets are from the 10th observing campaign of the NASA K2 mission, as well as high-resolution spectroscopy and speckle imaging follow-up observations. These newly-observed planets come from an initial set of 72 vetted candidates, which researchers subjected to a validation process incorporating pixel-level analyses, light curve analyses, observational constraints, and statistical false positive probabilities.

     An international team of astronomers pooled data from U.S. space agency NASA's Kepler and the European Space Agency (ESA)'s Gaia space telescopes, as well as ground-based telescopes in the U.S. Together with Dr. John Livingston, lead author of the study and a graduate student at the University of Tokyo, the team's combined resources led to the confirmed existence of these 44 exoplanets and described various details about them.    

      A portion of the findings yield some surprising characteristics: "For example, four of the planets orbit their host stars in less than 24 hours," says Dr. Livingston (we presume)."In other words, a year on each of those planets is shorter than a day here on Earth." These contribute to a small but growing list of "ultrashort-period" planets, so it could turn out they're not as unusual as they might seem.  

  

      "It was also gratifying to verify so many small planets," continues Dr. Livingston. "Sixteen were in the same size class as Earth, one in particular turning out to be extremely small -- about the size of Venus -- which was a nice affirmation as it's close to the limit of what is possible to detect."    The source observations for this study were made by Kepler, and they would not have happened were it not for a fault in 2013, which prevented accurate control of the space telescope. "Two out of the four control-reaction wheels failed, which meant Kepler couldn't perform its original mission to stare at one specific patch of the sky," explains Dr. Motohide Tamura of the University of Tokyo. "This led to its contingent mission, 'K2' -- our observations came from campaign 10 of this mission. We're lucky Kepler continues to function as well as it does."  

      The planets observed by K2 are known as transiting planets because their orbits bring them in front of their host stars, slightly reducing their brightness. However, other astrophysical phenomena can cause similar signals, so follow-up observations and detailed statistical analyses were performed to confirm the planetary nature of these signals. As part of his doctoral work, Dr. Livingston traveled to Kitt Peak observatory in Arizona to obtain data from a special type of camera, known as a speckle interferometer installed on a large telescope there. These observations, along with follow-up observations from a telescope in Texas, were necessary to characterize the host stars and rule out false positives.

       The combination of detailed analyses of data from these ground-based telescopes, K2 and Gaia enabled the precise determination of the planets' sizes and temperatures. The team's findings include 27 additional candidates that are likely to be real planets, which will be the subject of future research.

     Scientists hope to understand what kinds of planets might be out there, but can only draw valid conclusions if there are enough planets for robust statistical analysis. The addition of a large number of new planets, therefore, leads directly to a better theoretical understanding of solar-system formation. The planets also provide good targets for detailed individual studies to yield measurements of planetary composition, interior structure and atmospheres -- in particular, the 18 planets in several multiplanet systems. "The investigation of other solar systems can help us understand how planets and even our own solar system formed," says Livingston. "The study of other worlds has much to teach us about our own.

And no, I did not planet this way,

Steph 

To honor her 25 years on the planet Earth this month, here's Zoë, and the Peace Corps Malaria Elimination Team in Ethiopia. [Zoë is third from the right.]

Ch<i>ew</i>ing Gum Art from a friend.

Spin This News: Parental Chromosomes Develop Apart During Embryo's First Division

       Genetic researchers at the European Molecular Biology Lab (EMDL) have shown that mammalian life begins differently than originally suspected.

     It was long hypothesized that during a mammal embryo's first cell division, one spindle is responsible for segregating the embryo's chromosomes into two cells. Researchers now show that there are actually two spindles (as shown below), one for each set of parental chromosomes, meaning that the genetic information from each parent is kept apart throughout the first division.

     The publication Science published the results (which are likely to change biology textbooks) on 7/12/18. {Are there still textbooks?!}.

     This dual spindle formation may explain the high error rate in the early developmental stages of mammals, spanning the first few cell divisions. "The aim of this project was to find out why so many mistakes happen in those first divisions," says Dr. Jan (a guy!) Ellenberg, the group leader at EMBL who led the project. "We already knew about dual spindle formation in simpler organisms like insects, but we never thought (why not?!) this would be the case in mammals like mice. This finding was a big surprise, showing that you should always be prepared for the unexpected."

     Researchers have heretofore seen parental chromosomes occupying two half-moon-shaped parts in the nucleus of two-cell embryos, but it wasn't clear how this could be explained. "First, we were looking at the motion of parental chromosomes only, and we couldn't make sense of the cause of the separation," said Dr. Judith Reichmann. "Only when focusing on the microtubules -- the dynamic structures that spindles are made of -- could we see the dual spindles for the first time. This allowed us to provide an explanation for this 20-year-old mystery."

      Mitosis is the process of cell division, when one cell splits into two daughter cells. It occurs throughout the lifespan of multi-cellular organisms but is particularly important when the organism grows and develops. The key step of mitosis is to pass an identical copy of the genome to the next cell generation. For this to happen, DNA is duplicated and organised into dense thread-like structures known as chromosomes. The chromosomes are then attached to long protein fibres -- organised into a spindle -- which pulls the chromosomes apart and triggers the formation of two new cells. {The following diagram is one which will likely be updated in future embryology textbooks.}

     The spindle is made of thin, tube-like protein assemblies known as microtubules. During mitosis of animal cells, groups of such tubes grow dynamically and self-organize into a bi-polar spindle that surrounds the chromosomes. The microtubule fibres grow towards the chromosomes and connect with them, in preparation for chromosome separation to the daughter cells. Normally there is only one bi-polar spindle per cell, however, this research suggests that during the first cell division there are two: one each for the maternal and paternal chromosomes.

     "The dual spindles provide a previously unknown mechanism -- and thus a possible explanation -- for the common mistakes we see in the first divisions of mammalian embryos," Dr. Ellenberg explains. Such mistakes can result in cells with multiple nuclei, terminating development. "Now, we have a new mechanism to go after and identify new molecular targets. It will be important to find out if it works the same in humans, because that could provide valuable information for research on how to improve human infertility treatment, for example."

      In addition, the knowledge from this paper might impact legislation. In some countries, the law states that human life begins -- and is thus protected -- when the maternal and paternal nuclei fuse after fertilization. If it turns out that the dual spindle process works the same in humans, this definition is not fully accurate, as the union in one nucleus happens slightly later, after the first cell division.

     This discovery would have been impossible without the light-sheet microscopy technology (as seen above) developed at EMBL, which is now available through the spin-off company Luxendo. This allows for real-time and 3D imaging of the early stages of development, when embryos are very sensitive to light and would be damaged by conventional light microscopy methods. The high speed and spatial precision of light-sheet microscopy drastically reduce the amount of light that the embryo is exposed to, making a detailed analysis of these formerly hidden processes possible.

This is one spin we can stay with for awhile.
Steph

Earthquake experiment with brownies representing the stable craton of Canada and jello representing the tectonic plate boundary in Haiti.

The kids made "earthquake-proof" structures and observed the differences of the structures on "Canada" and "Haiti."

Precambrian Fossil Obama coronatus: Sessile Be De Millions?

     Earth's first complex animals were an eclectic group that lived in the shallow seas between 580-540 million years ago. 

     In great geologic irony, these more complex creatures are now classified as part of the very late Precambian ("Precambrian" means "before life.").

     The iconic Dickinsonia -- large, flat animals with a quilt-like appearance -- were joined by tube-shaped organisms, frond-like organisms that looked more like plants, and several dozen other varieties already characterized by geologists and biologists.

     We can add to that list two new animals discovered by a team of researchers:

     1) Obamus coronatus, a name that honors President Barack Obama's passion for science. This disc-shaped creature was between 0.5-2 centimeters. Obama coronatus is preserved in negative hyporelief and is defined by an overall torus shape produced by a series of arch-shaped spiral grooves. 

      Obamus coronatus (see below, left) was sessile or fixed, embedded to the ocean mat, a thick layer of organic benthic material that covered the early ocean floor. 

     2) Attenborites janeae, named after the English naturalist Sir David Attenborough for his science advocacy and support of paleontology (see above, right.) This tiny ovoid, less than a centimeter across, was adorned with internal grooves and ridges giving it a raisin-like appearance.

     The discovery of Obamus coronatus was published online on June 14, 2018, in the Australian Journal of Earth Sciences, or AJES, and the Attenborites janeae paper is forthcoming in the same journal. The studies were led by Dr. Mary Droser, a professor of paleontology at UC-Riverside.

     Both papers will be included in a 2019 AJES issue focusing on South Australia's Flinders Ranges region, where the discoveries were made.

     Part of the Ediacara biota, the soft-bodied animals are visible as fossils cast in fine-grained sandstone that have been preserved for hundreds of millions of years. These Precambrian lifeforms represent the dawn of animal life and are named after the Ediacara Hills in the Flinders Ranges, the first of several areas in the world where they have been found. Another suite of similar-age fossils was discovered in Sonora, Mexico, in 1995. (an area I worked in and described here).

     In the hierarchical taxonomic classification system, the Ediacara biota are not yet organized into families, and little is known about how they relate to modern animals. About 50 genera have been described, which often have only one species.

     "The two genera that we identified are a new body plan, unlike anything else that has been described," Droser said. "We have been seeing evidence for these animals for quite a long time, but it took us a while to verify that they are animals within their own rights and not part of another animal."

     The animals were seen in a particularly well-preserved fossil bed described in another paper published by Dr. Droser's group that will be included in the Flinders Ranges issue of AJES. The researchers dubbed this fossil bed "Alice's Restaurant Bed," a tribute to the Arlo Guthrie song and its lyric, "You can get anything you want at Alice's Restaurant."

     "I've been working in this region for 30 years, and I've never seen such a beautifully preserved bed with so many high quality and rare specimens, including Obamus and Attenborites," Dr. Droser said. "The AJES issue on the Flinders Ranges will support South Australia's effort to obtain World Heritage Site status for this area, and this new bed demonstrates the importance of protecting it."

You might say Ediacaran preservation is Flinders Keepers (for all).
Steph