A new fabric mimics polar bears’ pelts for warmth

 Link to article

The animal commonly known as the polar bear is called Ursus maritimus in taxonomic terminology. Japanese people call it the "white bear" (shiro kuma to be exact). There are about 26,000 of them currently living in the Arctic and Subarctic regions of Canada, Greenland, Norway, Russia, and the United States. We recognize them easily by their white fur, but these large maritime mammals hold a secret that scientists are discovering and putting to use in the garment industry.

Alaskan polar bear (Wikipedia)

Just how do polar bears keep warm? Temperatures in the Arctic waters are near freezing, and air temperatures are much colder. Researchers in the Department of Chemical Engineering at the University of Massachusetts Amherst studied polar bear skin and fur and designed a fabric to copy properties of their fur for better winter apparel. The first two things to know are that:

• polar bear hairs are translucent, almost colorless, and hollow
• polar bear skin is black

From snowbrains.com

Polar bears are actually covered with two layers of hair. The inner one is soft and dense, and the outer layer has long guard hairs that comprise most of the total body hair thickness. But the hollow center in each hair strand is not empty space. Hollow hairs are similar to those of alpaca, reindeer, and moose, but polar bear hairs are unique. 

Hollow hair showing core (left), larger magnification showing core material (right)

Because the hairs are clear, they reflect and scatter light from the sun. The light bounces around between hairs and even inside individual ones, as the diagram below shows.

Diagram from research by Kattab and Tributsch, 2015

Notice how light bounces and reflects off the hollow center and ricochets between hair fibers precisely with the physics and the properties of glass or plastic optical fibers. Light reaches the dark skin or reflects back and even luminesces (shines) to give the apparent white color of the bear. Researchers Kattab and Trubutsch used colored lasers to measure all of this. We normally think white materials reflect light, but remember that polar bear hair is not white. The black skin under the hair absorbs some of the incoming light and naturally radiates body heat, but the optical properties of the transparent keratin in the hair reflect and trap the heat radiation with the dark skin to keep the animal warm. This process also makes it difficult to use infrared radiation to detect polar bears, because the infrared radiation is trapped under the hair layers.

Dark polar bear skin works with fur to trap sunlight (Univ. of Massachusetts)

The University of Massachusetts researchers adapted this effect to design a material with two layers. The inner layer is made of nylon coated with a dark polymer called PEDOT, which is an excellent conductor of heat from light sources. To simulate the polar bear's hollow hairs, they added on top of the PEDOT a layer of transparent polypropylene threads that channel visible light down to the PEDOT. The new material is 30% lighter than cotton, too, and better at keeping the wearer warm. Direct sunlight is not needed to absorb energy as heat, so this can be used even on cloudy days. The University of Massachusetts researchers have coined the phrase "on-body greenhouse effect" to describe this material's function. The company Soliyarn, Inc. has already begun manufacturing this.

The material is not just good for retaining heat for the outdoors sporting industry. The material is touted at being useful for anyone working in the cold, whether they are conducting military operations or they simply have arthritis. Certain derivatives of PEDOT are also currently being investigated for use as wearable sensors for muscle and heart conditions, in a field known as "smart technology".

 

If you want to see a short (less than 2 minutes) video showing how polar bears can be white, gray, red, or even green, go to this link.

Scientists Revive Human Retinas after Death

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When we die, it takes time for cells in our body to completely shut down. Having enough oxygen and nutrients is important. It's not like a whole-body switch tells every cell to stop functioning all at once. that's why we can remove certain organs for transplantation; those organs are still in good condition but only for a short time (a few hours) after death. Nerve cells have the greatest problems in surviving when circulation is cut off, though. The retina of the the eye is tied directly to the optic nerve, and recently, researchers from the University of Utah learned that retina cells from the back of eyes can still function for a while after death. What's going on there?

In humans, the retina is a complex layer of 10 types of cells that covers the back two-thirds of the eye. When light hits the eye, it goes through the cornea and is focused by the lens through a large pocket of liquid making up the bulk of the eye's mass before striking the retina. That's when the seeing process begins.

Anatomy of the eye, showing layers of retinal cells

Corneas have been transplanted, and in rare cases so have tear ducts and eyelids. But how long do retinas survive death? It is known that within seconds of animals or humans dying, electrical activity between cells and oxygen supplies are depleted. At the same time, it takes longer (minutes) before blood sugar or energy molecules called ATP to be used up. Some experiments have shown partial brain recovery in various animals hours after death. The University of Utah researchers examined euthanized mice by implanting electrodes and measuring retinal responses to flashes of light every 5 seconds. In just 100 seconds after death, there is no response.

Then they euthanized the mice, removed the eye quickly, and surgically cut out the retina. This was fed an incoming stream of nutrients to feed the cells, give them oxygen, and control the pH. Again, they measured responses to flashes of light to see whether the retinal cells could be revived and respond like those in the whole eye. They examined the responses of the actual photoreceptor cells, which change the light energy into a signal, and the binary cells, which send that signal to nerves (ganglion cells) that then transmit the signal to the brain through the optic nerve.

Responses of retina cells kept alive after removal from the eye (Univ. of Utah)

What they saw was a clear difference between cells in the whole eye that didn't have life support vs. the same types of cells kept alive after removing them from the mouse eye. The photoreceptors seemed to keep a response longer than the binary cells, which could be important. If photoreceptor cells can function, but the binary cells can't send the message, that's the time limit to worry about.

So, for at least an hour after death, the binary cells could send a signal, but the photoreceptor cells stayed alive, and their function recovered, as long as 2-3 hours after death.

The researchers controlled the oxygen levels they delivered to the retinal cells. When they exposed them to less than 2.5% oxygen (what is expected in the body after death), they saw a nearly identical pattern of signal loss to what they measured in whole eye retinas. So, oxygen plays a very important role in maintaining the functionality of photoreceptor cells. Acidity showed a similar effect, too.

Mouse retinas have a greater number of photoreceptor cells called rods than humans. They help in low light conditions (useful for mice, because they are active at night). Humans have more cone photoreceptors (useful for distinguishing color). So, the Utah researchers also wanted to investigate retina tissue closer to humans in structure. They saw that nearly identical responses from eyes removed from macaques or human eyes donated 45 minutes to 2 hours after death by heart attack. Neither could not show a revival of retinal function, but they explained that in humans as due to the severe lack of oxygen caused by the heart attack. If the time after death was 20 minutes or less, recovery was possible.

The bottom line for future work is that transplantations will have to remove eyes extremely soon after death if they are going to be functional.

Here is a cool website with descriptions of the eye's anatomy. It has short videos showing the parts of the eye in 3D.

Introducing Janus, the exotic 'two-faced' white dwarf star

Reuters article link

What's all the fuss about a new white dwarf star? What is a white dwarf star anyway?

Our solar system was formed about 4.6 billion years ago. That includes the sun and planets. Ours is an average sun, just a typical one called a yellow dwarf star made of hydrogen and helium held together by gravity and brewing with nuclear fusion. It's about 100 times the diameter of the Earth, but much more massive, of course. It won't always be what you see. About 97% of the stars in our galaxy will eventually become white dwarfs.

Evolution of our average sun (Wikipedia)

Stars don't stay the same; they change over time as they burn the gaseous fuel inside them. The "burning" means the fusion of hydrogen into helium in the inner one-third of the sun's core. 

Our sun will soon cool down as the hydrogen runs out, and the helium at the center will contract even further. It will heat up and reignite fusion of the other two-thirds of the hydrogen which surrounds it. This will send out even more energy than before, and the star expands enormously. It'll be cooler, too, which means the color changes to red, and by then it will be called a red giant, about 400-500 times the original size.

Size of the red giant expected from Earth's sun (astronomynotes.com)

Gravity will eventually take hold, literally, and compress everything back again. Depending on the original mass, a star like ours will end up a hot white dwarf ("dwarf" because it'll be much smaller than before) after the red giant phase of its life. It will no longer fuse helium, but it will shine bright white because it will have the same mass of the original sun compressed into the size of the Earth! The helium will have fused into other elements like carbon and oxygen, and eventually iron at the core. It will cool down and shine only from the remaining heat, like a dying ember in a fireplace.

Cross section of a white dwarf 

All that will take another 5-7 billion years, so we have time. But we can look at white dwarf stars that have already formed. Recently, scientists have discovered a white dwarf star that is very odd. Its compressed helium and residual hydrogen aren't mixed together evenly. They aren't even in the two layers like the diagram above shows. Instead, they seem to be aggregated into separate halves of the white dwarf. As it rotates, the cooler helium makes it look darker. The existence of these two "faces" have given a reason to name it Janus, after the Roman god of two faces.

Artist's picture of Janus white dwarf (K. Miller, Caltech), and Janus the god (Wikipedia)

How can a white dwarf form like this? Nobody really knows  yet. You'd expect an even mixing of hydrogen and helium, or one at the center surrounded by the other like an egg shell. Not so for Janus! This weird half-hydrogen, half-helium two-faced star might be a phase in the development that will look like the diagram above. Scientists suggested that "if the magnetic field is stronger on one side than the other", then it might separate the hydrogen from the helium as they have seen. 

Finally, a white dwarf is expected to reach the final stage of its evolution: a black dwarf. This is when the white dwarf has fused all of the elements it possibly can with the temperatures it still has. It would hard to detect it because it would be very dim and cold; its influence on other objects due to its gravity would be the main way to know it's there. But, scientists have estimated that black dwarfs need longer than the current age of the universe (13.7 billion years) to reach that state, so it's going to take a while before we locate any.

Robert Hooke, an incredible polymath, the British da Vinci

Wikipedia entry

When I was in junior high, I learned that Robert Hooke was famous for coining the word cell in biology. He had looked through early microscopes and examined thin slices of cork, noting that they were made of a network of interconnected holes. These reminded him of empty rooms in monasteries; the rooms were known as cells, so the name fit. Hooke had actually seen and drawn cell walls, which are tough thick plant frameworks.

Hooke and his drawing of cork cells

Hooke published his findings and observations in a book Micrographia in 1665. The microscope had not been around very long, and he made his own modifications to create one with two lenses that provided combined magnification power over just one lens. Moreover, this design required adjusting the lens for better focus, instead of moving the specimen. A container of water focused light from a lamp tightly on the specimen. His observations on insects, sponges, bird feathers, and more caused the book to be an instant success. 

From micro.magnet.fsu.edu

But that is not the end of the story. Hooke was a polymath -- a person who has a great deal of knowledge and expertise in many fields. Compare him to another famous polymath, Leonardo da Vinci. Hooke was born on the Isle of Wight, England on July 18, 1635. His father noticed how adept he was at drawing and at building small mechanical objects and thought he'd be either an artist or clockmaker. But, Robert enrolled at the University of Oxford’s Christ Church College in 1653 and took up experimental science. He became an assistant to the famous chemist Robert Boyle, who himself belonged to an informal group called the "Philosophical College" or "Invisible College" that discussed a variety of scientific topics. Hooke designed most of Boyle's equipment and was later rewarded by being named Curator of Experiments for the Royal Society. The Society's motto was Nullus In Verba (Take Nobody’s Word For It), and this responsibility paved the way to Hooke's success in many areas of science.

He also studied physics and developed Hooke's Law of elasticity in 1660. This stated that the force required to extend or compress a spring (or many types of material) is proportional to the distance it is stretched or compressed. This had widespread applications for pressure gauges, scales, balance wheels of clocks, seismology, acoustics, and even simple things today like a ball pen spring, balloons, and toy guns. Hooke applied it to create the balance spring for pocket watches and improve the pendulum.

In 1665, he became professor of geometry at Gresham College in London. One year later, the "Great Fire of London" destroyed much of the city, and Hooke worked as a city surveyor with architect Christopher Wren to design streets and buildings to restore the city. 

Unknown painter (1675)

Hooke's polymath talents reached into paleontology and geology, too. During his time, nobody knew exactly how animal fossils arose. Some said there was a force in the Earth that simply shaped materials there to look like bones. He studied petrified wood and shell fossils under the microscope (a first for his time), and compared them to living samples. His conclusion was what we now know happens as minerals deposit into organic matter and replace it:

"this petrify'd Wood having lain in some place where it was well soak'd with petrifying water (that is, such water as is well impregnated with stony and earthy particles) did by degrees separate abundance of stony particles from the permeating water, which stony particles, being by means of the fluid vehicle convey'd, not onely into the Microscopical pores. . . but also into the pores or Interstitia. . . of that part of the Wood, which through the Microscope, appears most solid. . ." (reference here for more)

Pores of petrified wood (roberthooke.org.uk)

He spoke in 1670 about how gravity applied to all bodies in space and that the force of gravity between bodies decreases with the distance between them. That was 17 years before Isaac Newton published his Philosophiae Naturalis Principia Mathematica. 

In the book Discourse of Earthquakes, published after his death, Hooke recounted how the presence of seashells on mountains might have been due to them being underwater as a result of "some very great Earthquake." In studying coiled shells of three living cephalopods, Nautilus, Argonauta, and Spirula, compared with a fossil ammonite, he reached the conclusion that many fossils are simply organisms that no longer existed on Earth. This was a surprising thought of the day, that animals could go extinct, and wasn't solidified until the 1800s.

Hooke's ammonite fossils (Discourse of Earthquakes)

Hooke's passion for tinkering with the mechanical brought about many inventions at his hands:

• odometer to measure distance traveled on wheels
• universal joint used in cars today
• weather instruments like the anemometer (wind speed), hygrometer (humidity), & barometer
• a telescope
• an "otocousticon" hearing aid

Hooke's hygrometer (left) and drawings for a universal joint (right)

His various scientific discoveries also included the following:

• the Great Red Spot on the planet Jupiter
• the phenomenon of light diffraction and interference on thin films
• an attempt to prove the elliptical orbit of the Earth
• one of the first double star systems
• an early view of the wave function of light

Hooke died March 3, 1703 in London. There are no known portraits of him, just many disputed ones. It is rumored that Newton discarded all of the ones that were to be hung in the Royal Society as a result of disagreements they had had. He never mentioned Hooke in his book on gravity despite Hooke's earlier lecture. Hooke feuded a lot in his later years with other scientists, often over whether he'd arrived at some discovery first, but he was also known as a wonderful conversationalist on many topics in bars and coffeehouses. Some think that because of his outspoken nature, often failing to curb a sharp tongue, the lack of paintings was more over not caring to preserve them, instead of to destroy them.

The preface to his Micrografia perhaps sums up Hooke's view on science. Keep in mind this was written 300 years ago:

"By the means of telescopes, there is nothing so far distant but may be represented to our view; and by the help of microscopes, there is nothing so small, as to escape our inquiry; hence there is a new visible world discovered to the understanding."

This article in JSTOR is a brief but nicely detailed account of Robert Hooke.

Scientists discover game-changing bacterium that literally eats nuclear waste — here’s how it could protect us from toxins

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There are many types of bacteria in the world. One particular group is called an extremophile, which means it thrives only under extreme conditions such as high or low acidity, temperature, pressure, oxygen, etc. Bacteria consume many sorts of organic nutrients, too, and there are even some that use photosynthesis like plants to create their own. Some bacteria have symbiotic relationships with other creatures as well, like those in our gut, on our skin, or inside plant nodules. Whether they break food down or generate their own, bacteria energy sources to keep them alive, whether under normal or extraordinary environmental conditions. The energy can come from light or breaking down organic molecules (sugars or amino acids), or inorganic molecules (like minerals). But in recent years, scientists have discovered some bacteria that use radioactive materials and are not harmed by them. How is that possible?

How they get energy:

• Plants and some bacteria get energy directly from sunlight to put carbon dioxide and water together to make oxygen and organic compounds that store the energy. Photosynthesis is the name of that process, and it means taking light ("photo") to build ("synthesize") food containing energy.
• Another type of bacteria just digest organic molecules (big sugars, proteins, amino acids, etc.) into smaller sugars that store energy from the original material.
• A final type also digests organic material, but it needs minerals like iron or sulfur to provide some energy that gets incorporated into smaller molecules they store or digest to release that energy. 

In 1956, Arthur Anderson and his research team from the Oregon Agricultural Experiment Station in Corvallis, Oregon were studying how to sterilize canned foods. They hit them with gamma radiation strong enough to kill all forms of life (250 times stronger than what kills ordinary bacteria), but they discovered a bacteria that survived. Soon afterward, similar bugs were found in sausage, fish, and air samples, as well as English soil, granite in Antarctica, animal feces in a zoo, and a shielding pool for cobalt radiation. It's everywhere.

Anderson's bacteria was named Micrococcus radiodurans. "Micro" means small, and "coccus" refers to the spherical shape. It might be found singly, in pairs, or in groups of four. The species name suggests its durability to radiation. Later, this was identified genetically as a new genus, so the name changed to Deinococcus radiodurans, where "deino" means terrible. 

A tetrad of Deinococcus radiodurans (Wikipedia)

Since Anderson's discovery, many other bacteria have been shown to be highly resistant to UV and ionizing radiation. "Highly resistant" needs some clarification. A chest X-ray produces 0.0001 rads of radiation, and humans die when exposed to 500 rads. But D. radiodurans can survive 500,000 rads with no loss of viability, and a third of its population is still around after exposure to 1,500,000 rads (more than what was in the atomic bombs at Hiroshima and Nagasaki)! So, how do they do it?

Gamma rays and X-rays pass through cellular material and cause breaks in one or both strands of the DNA molecule. That can be enough to cause problems in the cells' ability to reproduce.

From Jobilize.com

Virtually all life has built-in mechanisms to protect or repair the day to day damage to its DNA. This daily damage can occur from exposure to sunlight or chemicals in the environment or the body, so it's important for creatures to have an efficient repair system operating. Deinococcus radiodurans, like most bacteria and other creatures, has DNA shaped like a twisted ladder (double helix). However, instead of being assembled in string-like strands or chromosomes, it's in an unbroken circle. 

The DNA repair tools that this bacteria use are similar to the ones in many other life forms, but they work much faster and more efficiently (fixing >100 breaks in one DNA molecule compared to 2 or 3 by other bacteria). Its unique repair system can heal hundreds to thousands of DNA breaks per cell, while regular bacteria can only tackle a few dozen before dying.

Normal repair tools fix problems if one strand in the DNA ladder is damaged. But if both strands of the DNA are damaged, those other tools are needed, but another copy of the DNA is needed to serve as a template to copy the correct broken pieces. Fortunately, D. radiodurans has 4-10 sets of its DNA, more than other bacteria, that it can use in this way.

D. radiodurans not only repairs itself, but it has a protection mechanism as well. Damage from ionizing radiation is lethal mostly because it generates free radicals of oxygen, which cause DNA injury. This is mediated by high concentrations of manganese which D. radiodurans seems to stockpile. The manganese protects the DNA repair proteins instead of the DNA itself.

Put these repair tools and protection mechanism together, and it isn't surprising that D. radiodurans is often called "Conan the Bacterium", suggesting its strength to survive. Look below at a comparison with a common bacteria.

Survival of D. radiodurans vs E. coli against gamma rays (Minton, 1994)

When some bacteria use minerals like iron or sulfur in their metabolism, they change the mineral from one form to another. In the case of iron, they take it from the water, use it, and leave its chemically changed form to settle out on the bottom instead of remaining dissolved. Some bacteria like D. radiodurans can be engineered to do the same thing with radioactive materials. Their natural ability to survive radiation keeps them around for the newly genetically engineered metabolism to operate. Its byproducts settle out and allow for bioremediation in areas where the dangerous minerals like uranium are dissolved in water. Lab experiments, for example, show a 90% removal of uranium in 6 hours in this way.

This process has also been shown to work for other dangerous, non-radioactive materials. For example, D. radiodurans has the ability to survive radiation from uranium, and by splicing into its DNA a gene to tolerate and convert mercury, scientists have been able to clean up waste sites of the mercury. Since a third of the 3,000 waste sites in the U.S. are leaking into the ground, this multi-billion dollar cost can be greatly reduced with such a treatment.

Radiation-resistant bacteria can also be beneficial in another way. They make chemicals called extremolytes (extreme metabolites) like UV protecting proteins for their own survival. Some of these can be used as sunscreens or antioxidants.

The antioxidants made by these special bacteria can be used to improve vaccines, too. Vaccines made by irradiating the virus or bacteria you want to generate an immune response are more effective than those made by heating or chemically treating the bugs. The radiation destroys the bug's DNA, but it can also destroy a protein that generates the desired immune reaction, unless it is protected by adding the antioxidant from a radiation-resistant bacteria.

D. radiodurans manganese protecting vaccine particle (Gayen et al, 2017)

Tough Deinococcus radiodurans has been found all over the Earth, and because of its resistance to radiation, acidity, and drying, some have said it might be one of the earliest organism on the planet. Others suggest it might have been transplanted here from Mars when it was ejected from collisions with meteors. Whatever the case, studying it may help us learn not only what is out there in the cosmos, but also how to protect ourselves from radiation damage.