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Tuesday, July 26, 2016

Hooked on Phononics: Spider Silk Sound and Heat

      New discoveries about spider silk could inspire new materials to manipulate heat and sound in the same way semiconducting circuits manipulate electrons, according to scientists at Rice University.

      A paper published yesterday in Nature Materials looks at the microscopic structure of spider silk and reveals unique characteristics in the way it transmits phonons, quasiparticles of sound.

      A phonon (cool moving graphic at this link) is a collective excitation in a periodic, elastic arrangement of atoms or molecules in condensed matter, like solids and some liquids. It represents an excited state in the quantum mechanical quantization of the modes of vibrations of elastic structures of interacting particles.

     The research shows for the first time that spider silk has a phonon band gap. That means it can block phonon waves in certain frequencies in the same way an electronic band gap -- the basic property of semiconducting materials -- allows some electrons to pass and stops others.

     The researchers wrote that their observation is the first discovery of a "hypersonic phononic band gap in a biological material."

      How the spider uses this property remains to be understood, but there are clear implications for materials, according to materials scientist and Rice Engineering Dean Edwin Thomas, who co-authored the paper. He suggested that the crystalline microstructure of spider silk might be replicated in other polymers. That could enable tunable, dynamic metamaterials like phonon waveguides and novel sound or thermal insulation, since heat propagates through solids via phonons.

     "Phonons are mechanical waves," Thomas said, "and if a material has regions of different elastic modulus and density, then the waves sense that and do what waves do: They scatter. The details of the scattering depend on the arrangement and mechanical couplings of the different regions within the material that they're scattering from."

       Spiders are adept at sending and reading vibrations in a web, using them to locate defects and to know when "food" comes calling. Accordingly, the silk has the ability to transmit a wide range of sounds that scientists think the spider can interpret in various ways. But the researchers found silk also has the ability to dampen some sound.

      "(Spider) silk has a lot of different, interesting microstructures, and our group found we could control the position of the band gap by changing the strain in the silk fiber," Thomas said. "There's a range of frequencies that are not allowed to propagate. If you broadcast sound at a particular frequency, it won't go into the material."

     Thomas and other researchers decided to take a more detailed look at dragline silk, shown below in a SEM, which spiders use to construct a web's outer rim and spokes and as a lifeline. (A spider suspended in midair is clinging to a dragline.) Though silk has been studied for thousands of years, it has only recently been analyzed for its acoustic properties.

      "Silk is a hierarchical structure comprised of a protein, which folds into sheets and forms crystals. These hard protein crystals are interconnected by softer, amorphous chains," Thomas said. Stretching or relaxing the interconnecting chains changes the silk's acoustic properties by adjusting the mechanical coupling between the crystals.

       "Right now, we don't know how to do any of this in other macromolecular fiber materials," Thomas said. "There's been a fair amount of investigation on synthetic polymers like nylon, but nobody's ever found a band gap."

Have you ever found a band gap?!

Zoƫ and her "Camp English" group in Ethiopia this summer:

Wednesday, July 20, 2016

Geological Mystery Feature: Alluvial Platinum from Russia

          Any guesses as to the origin of this circular geomorphic feature?

    It's not a crater and it's not a volcano. . .

      It is in northeast Russia and it's the source of alluvial (think panning for gold) platinum. . .

     This landform is nearly perfectly circular, with a diameter just under 8 kilometers (5 miles) and a ridge about 600 meters tall. A river has eroded through the lip, draining rainwater and runoff out of the center. The ridge is bare rock, with vegetation growing both inside and outside the ring. 

     Any ideas? Guess now or read on. . .
     Kondyor Massif is an igneous intrusion piercing the surrounding sedimentary rock without ever forming a volcano or erupting from a crater. A column originally topped by a dome when it formed, 

the structure has undergone differential erosion so the softer material weathered and eroded first, leaving the harder ring behind with the rest of the column hidden below the surface.

       The Kondyor Massif located in Khabarovsk Krai, Far Eastern Federal District, Russian Federation, roughly 600 km (373 mi) west-to-southwest of Okhotsk, or some 570 km (354 mi) south-east of Yakutsk.  

       Slow cooling produced these valuable platinum specimens which are up to 1.5 cm in diameter. They later weather out of the Massif and are mined alluvially.

       How was you guess; did you use circular reasoning? :-)  Have you ever panned for platinum, silver, or gold?


Wednesday, July 13, 2016

BUM in the Ocean: In Situ Microscopy "Polyps" Into View

           Benthic Underwater Microscopy (BUM) is a new technology for studying coral polyps and other microscopic organisms in situ.

       The exquisite and delicate structures of the benthic ecosystems are analyzed and photographed at the bottom of the sea floor.

      The microscope features an extremely high-resolution camera, an underwater computer with a diver interface, bright LED lights for fast exposure images, and a flexible, tunable lens that allows scientists to view underwater structures in 3D.

     Millions of polyps work together to build coral reefs by secreting calcium carbonate, with the minute animals providing nutrients and color to the reef.


      Using the BUM microscope, scientists were able to position themselves 5 centimeters away from the polyps and watch them as they captured tiny plankton and brine shrimp with tiny swaying tentacles.

     Researchers left the microscopes out overnight in order to record the polyps over an extended period. The images and footage gathered show the polyps’ gentle “dancing” and post-meal "kisses" that scientists say could be a way for polyps to share nutrients throughout the coral colony.

     Images from the Benthic Underwater Microscope also revealed a more violent side to the secret lives of polyps, showing coral of different species conquering weaker specimens. In order to win more reef space, the conquering coral will emit filaments that secrete stomach enzymes to destroy the tissue of their competitors.

     Researchers have used the BUM in two places so far, the waters off of Maui and the coast of Israel. With some of the largest coral bleaching events ever recorded taking place this year, scientists were especially interested to study the hard-hit coral reefs off of Maui.

     With the help of the new microscopic tool, scientists discovered that in bleached areas, there is a honeycomb pattern of algal colonization (like underwater squatters, algae move in when coral is weak from bleaching) and algal growth around individual polyps on the coral.

     When coral are weak, scientists found, algae are able to outgrow and smother the already struggling reefs.

       The new BUM technology is promising for understanding subsea micro-organisms, especially coral polyps.

          Lastly, this unrelated image made me laugh today. Hope you enjoy as well!

Hope you wonder at the new technology that has "polyps" into view.

Any ideas as to what this flower is? Thistle-like. . .but different. It's growing in West Chicago Creek, Colorado. 

Tuesday, July 5, 2016

Bac(teria) To The Future: Two Bacterial Types Helpful in Vaccine Transport and in Blocking Zika Transmission

          Yeah! The rest of the USA may be celebrating the fourth of July but we here at Partial Ellipsis of the Sun are celebrating bacteria. Two research publications published the first week of July note the role of two kinds of bacteria in being a vaccine transport capsule and in blocking Zika virus transmission. 

     Researchers experimenting with harmless strains of E. coli have developed an E. coli-based transport capsule designed to help next-generation vaccines do a more efficient and effective job than today’s immunizations.

       The research, described in a study published July 1, 2016, in the journal Science Advances, highlights the capsule’s success in fighting pneumococcal disease, an infection that can result in pneumonia, sepsis, ear infections and meningitis.

     “It’s a bit counterintuitive given what you hear about E. coli, but there are many strains of the bacteria, most of which are perfectly normal in the body, that have great potential to fight disease,” said Blaine A. Pfeifer, PhD, associate professor of chemical and biological engineering in the University at Buffalo School of Engineering and Applied Sciences.

      The core of the transport capsule is harmless E. coli. A synthetic polymer — poly (beta amino ester), or PBAE — wraps around the bacteria and resembles a chain link fence. The positive-charged polymer, combined with the negative-charged bacteria cell wall, create a sort of hybrid capsule.

     To test the capsule, the researchers then inserted a protein-based vaccine, designed to fight pneumococcal disease. The results, when tested in mice, were impressive.

     The capsule’s hybrid design provided:

·         Both passive and active targeting of specific immune cells called antigen-presenting cells that trigger an immune response.

·         Natural and multicomponent adjuvant properties, which enhance the body’s immune response.

·         Dual intracellular delivery mechanisms to direct a particular immune response.

·         Simultaneous production and delivery of the components (antigens) required for a vaccine.

·         Strong vaccination protection capabilities against pneumococcal disease.

     It’s also relatively inexpensive to create and flexible in terms of use. For example, the capsule could be used as a delivery device for therapies that target cancer, viral-based infectious disease and other illnesses.

      And that's not all!

       This same week, researchers
 at the University of Wisconsin have confirmed that a benign bacterium called Wolbachia pipientis can completely block transmission of Zika virus in Aedes aegypti. Scientists say the bacteria could present a 'novel biological control mechanism,' aiding efforts to stop the spread of Zika virus.

       Other research with Wolbachia pipientis has previously shown that the bacterium is an effective tool in stopping transmission of mosquito-borne viruses. The newest research, stepped up due to the Summer Olympics in Brazil, is quite promising.

         Indeed, Bac(teria) to the Future is here! 

Happy July from the PEOTS Staph, ;-)