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Wednesday, November 30, 2016

Blue-Leaved Begonias and Fibonacci Golden Spirals

       Some leaves of certain species of begonias in Malaysia are luminescent blue in order to harvest maximum energy in low-light conditions.

      The begonias’ chloroplasts, which use photosynthesis to convert light into fuel, have a repeating structure that allows the plants to efficiently soak up light. This is important for plants that live on the shady forest floor. 

     The structure acts as a “photonic crystal” that preferentially reflects blue wavelengths of light and helps the plant better absorb reds and greens for energy production, researchers report in the October 24, 2016 issue of Nature.

     Colors in plants and animals typically come from pigments, chemicals that absorb certain wavelengths, or colors, of light. In rare cases, plants and animals derive their hues from microstructures. In begonias, such tiny, regular architectures can be found within certain chloroplasts, known as iridoplasts. As light bounces off these structures within an iridoplast, the reflected waves interfere at certain wavelengths creating a blue, iridescent shimmer.

     These contain regularly spaced stacks of three to four 'thylakoids' - which resemble a photonic crystal and strongly reflect wavelengths of light between 430 and 560 nanometers.

      The thylakoids look very similar to the artificial structures commonly used to make miniature lasers that control the flow of light. Studies of low light gathering in begonias may prove useful in improving the sharpness of color on computer and Smart phone screens.

      The iridoplasts concentrate these specific wavelengths onto the plant's photosynthetic apparatus, increasing the efficiency of its photosynthesis by 5 to 10 percent. 

      Those structured chloroplasts also offer a survival benefit; they help the plants collect light. In a hybrid of two species, Begonia grandis and Begonia pavonina, the structures enhance the absorption of green and red wavelengths by concentrating these rays on light-absorbing compartments within the iridoplasts. Importantly, the structures slow the light. The “group velocity,” or the speed of a packet of light waves, is decreased due to interference between incoming and reflected light. The slowdown gives the plant more time to absorb precious sunbeams.

     “These iridoplasts can basically photosynthesize at low-light levels where normal chloroplasts just simply could not photosynthesize,” says study coauthor Dr. Heather Whitney, a plant biologist at the University of Bristol, England. Iridoplasts, however, can’t hold their own in bright light. So begonias also have standard chloroplasts, which provide energy in plentiful sunshine. Iridoplasts act like “a backup generator” in dim conditions,  Dr. Whitney says.

      The Fibonacci Golden spiral on some begonia leaves is a luminescent bonus!

Blue and Fibonacci, what a duo!


Friday, November 25, 2016

The Corundum Conundrum: Sapphires, Rubies, and Padparadscha

      Ah! The Corundum Conundrum; isn't that a perfect mineralogical riddle for this age of the Dum-Dum?! Corundum, as well as the lollipop, occurs in a wide variety of colors.

      Corundum is the crystalline form of aluminium oxide, Al2O3, generally containing traces of iron, titanium, vanadium and/or chromium. The blue, green, orange, yellow, purple and clear gem varieties are all sapphires.

        The red, gemmy varieties of corundum are called rubies.

      And, new to me, the pink-orange exotic gem variety is named padparadscha. The word is derived from the Sanskrit or Sinhalese padma raga, meaning “lotus color” and refers to the pink-orange color, similar to the lotus flower. Natural padparadscha is among the rarest and most highly prized varieties of corundum.

     The word "corundum" is derived from the Tamil word Kurundam which originates from the Sanskrit word kuruvinda meaning ruby.

     Because of corundum's hardness (corundum has a hardness of 9.0 on Mohs hardness scale), it can scratch almost every other mineral, except diamond. The hardness of corundum is 1/400 that of diamond.

       Corundum is used as an abrasive in sandpaper and in machining metals, plastics, and woods.

      Corundum belongs to the hexagonal crystal group (Recall the PEOTS post on Sapphire of the Sea).

      In addition to its hardness, corundum is very dense at 4.02 g/cm^3, which is very high for a transparent mineral composed of the low-atomic mass elements of aluminium and oxygen.

      Atomic numbers of 13 for aluminum and 8 for oxygen, both Fibonacci numbers, can't be a corundrum conundrum coincidence, can it?

      Let's see, hard, very dense, and colorful: where have we heard that corundum conundrum before? Riddle me Ruby? Dumped on by the Dum-Dums? 

     Happy Colorful (not Black) Friday from the wonderful colors of Zoë and friends in Ethiopia!

Very Thankfully,

Tuesday, November 15, 2016

YIMBY: Yes, In My Back Yard: Block Island Wind Farm Begins Operations

      The five wind turbines south and east of Block Island, Rhode Island, USA, are newly operational as the Block Island Wind Farm, the first such offshore farm in the US.

         I learned about the Block Island Wind Farm from my mom who saw one of my high school friends, Ms. Judith Gray, a Block Island resident and retired meteorologist at the National Oceanic and Atmospheric Administration, on the national news last week.

        In a 2014 article, Ms. Gray noted she has seen the damage caused by fossil fuels firsthand after visiting the site of the Exxon Valdez oil spill in Alaska and the Deepwater Horizon accident in the Gulf of Mexico. "Renewable energy does not pose the same risks," said Ms. Gray, whose home on Block Island is in view of the location of the wind farm.

     We spoke about wind energy about two years ago at  Partial Ellipsis of the SunIn a gust of very good news for the renewable energy sector, a survey of 163 wind energy experts has found that in the coming decades, the cost of electricity generated by wind should plunge, by between 24 and 30 percent by the year 2030, and even further by the middle of the century.

      One key reason for the lowered costs is that new wind projects are about to get even more massive, in both the offshore and onshore sectors. As turbines get taller and access stronger winds, and as rotors increase in diameter, it becomes possible to generate ever more electricity from a single turbine.

     The Block Island Wind Farm will now produce enough electricity to power 19,000 homes or 90 percent of the island's needs, with 30 megawatts.

     Seems like a Wind-Wind to me,

Happy Thanksgiving! SCIENCE IS SCIENCE, thankfully.

Thursday, November 10, 2016

Giant Sloth Coprolite From Nevada: This Poop is Fair to Midden

      An extinct giant sloth once used a spacious cave in Nevada not just as a shelter but also as a huge outhouse, leaving droppings on the cave floor whenever nature called. Now, scientists have analyzed the sloth's mummified dung (which is also known as a midden) and determined what plants the animal ate most frequently, according to new research.

      Chemical analyses of the fossilized poop, known as coprolites, revealed that the ancient sloths primarily ate an orange-flowered perennial shrub known as desert globemallow (Sphaeralcea ambigua),

 a shrub called Mormon tea (Ephedra

and a drought-tolerant plant known as saltbush (Atriplex), said Ryan Haupt, Department of Geology and Geophysics at the U. of Wyoming.

      Scientists have known about the coprolites in southern Nevada's Gypsum Cave since the 1930s. 

      The Shasta ground sloth,  Nothrotheriops shastensis, lived in the cave at different points, from about 36,000 to 11,000 years ago, Haupt said.

      "Radiocarbon dates from the coprolites correlate with periods where the climate was a bit cooler, and since we know that modern tree sloths don't thermoregulate very well, it's possible that these ground sloths were going into the cave to keep warm," Haupt said.

     To complete the analysis, Haupt needed only a few milligrams of each coprolite. After grinding the small samples with a mortar and pestle, he analyzed the specimens for different carbon and nitrogen isotopes.

      Plants that live in dry, hot or otherwise water-stressed environments have evolved strategies to prevent themselves from drying out, such as absorbing sunlight during the day but absorbing carbon dioxide only at night. These strategies also affect the chemical pathways used during photosynthesis, resulting in different ratios of heavy and light stable carbon isotopes in the plants. These ratios work their way up the food chain when animals eat these plants, so by measuring the ratios, Haupt was able to see what plants the sloths chose to eat.

     The analysis fits with the saying, "'You are what you eat,' but down to the atomic level," Haupt said.

      The new results correlate with previous findings that were reached using different methods. For instance, some scientists looked for identifiable plants within the mummified excrement, either under a microscope or based on the plants' DNA, he said. The plants identified in previous studies match the ones Haupt recognized in the isotope analysis.

     But not all species of extinct sloths left behind coprolites, which makes it difficult to compare the diet of the Shasta ground sloth with that of related sloths. Luckily, this molecular analysis, known as stable isotopic analysis, can also be applied to analyses of sloth bones and teeth, "which is pretty neat," Haupt said.

     For instance, the Shasta ground sloth was more of a mixed feeder than other ancient sloths were, including those in the Megatheriidae and Mylodontidae families, Haupt found when he compared the Shasta ground sloth results with already-published values from the bones and teeth of other sloths.

      Timothy Gaudin, a professor at the University of Tennessee at Chattanooga, who was not involved in the study, said the research is encouraging because it requires only a small piece of the coprolite for analysis.

      "In the past, there have been studies on these, but what they've had to do is literally take the coprolites apart, pull all of the little plant parts out and try to identify them one at a time," Gaudin said. "And then you end up with no specimen."

       And so, despite the fact that this happens:


       This also happens (My favorite sloth image from Costa Rica with Zoë).


"Bombs" atop PVC pipe "missile silos" built by kindergartners on Friday. Sigh.

Tuesday, November 1, 2016

Popeye's Spinach Was Never Like This: The Superfood Is Also An Explosives Detector!

     Spinach is no longer just a superfood. By embedding spinach leaves with carbon nanotubes, MIT engineers have transformed spinach plants into sensors that can detect explosives, wirelessly relaying that information to a handheld device similar to a smartphone.

     This is one of the first demonstrations of engineering electronic systems into plants, an approach that the researchers call plant nanobionics. "The goal of plant nanobionics is to introduce nanoparticles into the plant to give it non-native functions," says Dr. Michael Strano, the leader of the research team.

      A carbon nanotube is a tube-shaped material, made of carbon, having a diameter measuring on the nanometer scale. A nanometer is one-billionth of a meter or about 10,000 times smaller than a human hair. The bonds in carbon nanotubes are extremely strong.

     In this case, the plants were designed to detect chemical compounds known as nitroaromatics, which are often used in landmines and other explosives. When one of these chemicals is present in the groundwater sampled naturally by the plant, carbon nanotubes embedded in the plant leaves emit a fluorescent signal that can be read with an infrared camera. The camera can be attached to a small computer similar to a smartphone, which then sends an e-mail to the user.

     "This is a novel demonstration of how we have overcome the plant/human communication barrier," says Strano, who believes plant power could also be harnessed to warn of pollutants and environmental conditions such as drought. Strano is the senior author of a paper describing the nanobionic plants in the October 31, 2016, issue of Nature Materials

     Two years ago, in the first demonstration of plant nanobionics, Strano and others used nanoparticles to enhance plants' photosynthesis ability and to turn them into sensors for nitric oxide, a pollutant produced by combustion.

      "Plants are very good analytical chemists," Strano says. "They have an extensive root network in the soil, are constantly sampling groundwater, and have a way to self-power the transport of that water up into the leaves."

      Strano's lab has previously developed carbon nanotubes that can be used as sensors to detect a wide range of molecules, including hydrogen peroxide, the explosive TNT, and the nerve gas sarin. When the target molecule binds to a polymer wrapped around the nanotube, it alters the tube's fluorescence.

      In the new study, the researchers embedded sensors for nitroaromatic compounds into the leaves of spinach plants. Using a technique called vascular infusion, which involves applying a solution of nanoparticles to the underside of the leaf, they placed the sensors into a leaf layer known as the mesophyll, which is where most photosynthesis takes place.

      They also embedded carbon nanotubes that emit a constant fluorescent signal that serves as a reference. This allows the researchers to compare the two fluorescent signals, making it easier to determine if the explosive sensor has detected anything. If there are any explosive molecules in the groundwater, it takes about 10 minutes for the plant to draw them up into the leaves, where they encounter the detector.

     To read the signal, the researchers shine a laser onto the leaf, prompting the nanotubes in the leaf to emit near-infrared fluorescent light. This can be detected with a small infrared camera connected to a Raspberry Pi, an inexpensive credit-card-sized computer similar to the computer inside a smartphone. The signal could also be detected with a smartphone by removing the infrared filter that most camera phones have, the researchers say.

      Using this setup, the researchers can pick up a signal from about 1 meter away from the plant; they are working on increasing that distance.

      The researchers have also genetically engineered spinach plants that can detect dopamine, which influences plant root growth, and they are now working on additional sensors, including some that track the chemicals plants use to convey information within their own tissues.

     "Plants are very environmentally responsive," Strano says. "They know that there is going to be a drought long before we do. They can detect small changes in the properties of soil and water potential. If we tap into those chemical signaling pathways, there is a wealth of information to access."

     These sensors could also help botanists learn more about the inner workings of plants, monitor plant health, and maximize the yield of rare compounds synthesized by plants such as the Madagascar periwinkle, which produces drugs used to treat cancer.

     Remember all that talking to plants research in the 1970's? Well, now the plants are talking back!

What are your plants saying?