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Comment by Dr. Krishna Kumari Challa on December 24, 2021 at 10:48am

Comets' heads can be green, but never their tails. We finally know now why.

 Every so often, the Kuiper Belt and Oort Cloud throw galactic snowballs made up of ice, dust and rocks our way: 4.6-billion-year-old leftovers from the formation of the solar system.

These snowballs – or as we know them, comets – go through a colourful metamorphosis as they cross the sky, with many comets’ heads turning a radiant green colour that gets brighter as they approach the Sun.

But strangely, this green shade disappears before it reaches the one or two tails trailing behind the comet.

Astronomers, scientists and chemists have been puzzled by this mystery for almost a century. In the 1930s, physicist Gerhard Herzberg theorised the phenomenon was due to sunlight destroying diatomic carbon (also known as dicarbon or C2), a chemical created from the interaction between sunlight and organic matter on the comet’s head – but as dicarbon isn’t stable, this theory has been hard to test.

A new UNSW Sydney-led study, published in Proceedings of the National Academy of Sciences (PNAS), has finally found a way to test this chemical reaction in a laboratory – and in doing so, has proven this 90-year-old theory correct.

This explains why the green coma – the fuzzy layer of gas and dust surrounding the nucleus – shrinks as a comet gets closer to the Sun, and also why the tail of the comet isn’t green.

The key player at the centre of the mystery, dicarbon, is both highly reactive and responsible for giving many comets their green colour. It’s made up of two carbon atoms stuck together and can only be found in extremely energetic or low oxygen environments like stars, comets and the interstellar medium.

Dicarbon doesn’t exist on comets until they get close to the Sun. As the Sun starts to warm the comet up, the organic matter living on the icy nucleus evaporates and moves to the coma. Sunlight then breaks up these larger organic molecules, creating dicarbon.

The UNSW-led team have now shown that as the comet gets even closer to the Sun, the extreme UV radiation breaks apart the dicarbon molecules it recently created in a process called ‘photodissociation’. This process destroys the dicarbon before it can move far from the nucleus, causing the green coma to get brighter and shrink – and making sure the green tinge never makes it into the tail.

This is the first time this chemical interaction has been studied here on Earth.

1. Jasmin Borsovszky, Klaas Nauta, Jun Jiang, Christopher S. Hansen, Laura K. McKemmish, Robert W. Field, John F. Stanton, Scott H. Kable, Timothy W. Schmidt. Photodissociation of dicarbon: How nature breaks an unusual multiple bond. Proceedings of the National Academy of Sciences, 2021; 118 (52): e2113315118 DOI: 10.1073/pnas.2113315118

Comment by Dr. Krishna Kumari Challa on December 24, 2021 at 8:43am

Circumstantially, microplastics have also been shown to stir up trouble by generating reactive oxygen species that are known to play a role in inflammation.

With that in mind, it's not at all surprising to imagine an increase in gut exposure to microplastic particles might play a similar role to certain microbes in sensitizing the lining to an exaggerated immune reaction.

Further studies will be needed before we can claim with any confidence that our dietary supplement of plastic dust is putting us at increased risk of any health problems. There are still too many unknowns.

But that doesn't mean we shouldn't be taking action. Evidence that the rising tide of plastic waste is affecting everything from the climate to the distribution of species to the health of marine life is mounting.

That our health might be just one more consequence is just more reason to wean ourselves off our dependence on this pervasive pollutant.

https://pubs.acs.org/doi/10.1021/acs.est.1c03924

https://www.sciencealert.com/inflammatory-bowel-disease-feces-found...

Part 3

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Comment by Dr. Krishna Kumari Challa on December 24, 2021 at 8:42am

Seven million people globally were diagnosed with IBD in 2017, a condition distinguished by regular bouts of discomfort and changes in bowel motion produced by a hair-trigger system overreacting to otherwise benign materials in the gut. 

The illness usually falls into one of two main diagnoses: Crohn's disease, which is typically characterized by an inflamed lining throughout the deeper layers of the digestive tract, and ulcerative colitis, which is marked by ulcers in the large intestine's lining.

In either case, the ultimate source of the errant immune response isn't yet fully understood, though suspicions lie with the complex way our guts negotiate diplomatic relations with our microflora, particularly during an infection.

Whether plastic particles might somehow involve themselves with a link in this chain has never been fully made clear, though animal studies have previously pointed to gut inflammation as a possible side effect of microplastic exposure.

Part 2

Comment by Dr. Krishna Kumari Challa on December 24, 2021 at 8:42am

Alarming Levels of Microplastics in The Feces of People With Irritable Bowel Diseases or IDB

A recent investigation by a team of researchers in Nanjing, China, has uncovered worrying signs that elevated levels of microplastics could be inflaming our digestive systems.

Feces collected from 52 individuals diagnosed with inflammatory bowel disease (IBD) were found to contain around 1.5 times the number of plastic particles smaller than 5 millimeters (about 0.2 inches) than similar samples from volunteers without any chronic illnesses.

The vast majority of plastic particles were smaller than 300 micrometers, with a few detectable pieces coming in below a minuscule 5 micrometers across. The researchers noticed those with IBD also tended to have a greater proportion of smaller flakes of microplastic.

What's more, the greater the plastic load, the more severe the individual's IBD symptoms. 

A survey revealed nothing unusual about the origins of the plastic, suggesting it was the kinds of particles we all might ingest by drinking from PET bottles or eating out of single-use disposable containers.

As an observational study, the research doesn't establish cause and effect. Nobody can claim the difference in microplastic load is solely, or even partially responsible for the symptoms of diarrhea, rectal bleeding, and abdominal cramping associated with the illness.

It's even possible having IBD might make it harder to clear the build-up of plastic detritus that accumulates in our diets.

But the mere possibility of a connection is concerning enough to warrant further investigation, especially given the shocking rate at which plastic waste is spreading virtually unabated.

Part 1

Comment by Dr. Krishna Kumari Challa on December 24, 2021 at 8:35am

Scientists Just Identified a Brand New Muscle Layer in The Human Jaw

Undoubtedly there are still exciting new discoveries to be made in a field as well-studied as human anatomy: researchers have confirmed the existence of a layer of muscle in the human jaw that has until now eluded anatomists.

This new muscle is a deeper, third section of the masseter muscle. It's the most prominent jaw muscle: press your hand against the back of your jaw while you chew and you'll feel it moving.

Typically represented as having just two layers, there has been suspicions based on animal studies that there is more to its structure. However until now, attempts to describe it have been contradictory and confusing.

Through an analysis of more than two dozen human heads – including one living subject and 12 heads preserved in formaldehyde – it's been established through a new study that the masseter muscle does indeed have three distinct sections, not two.

This deep section of the masseter muscle is clearly distinguishable from the two other layers in terms of its course and function.

The name Musculus masseter pars coronidea, or the coronoid section of the masseter, has been proposed for the new muscle layer by the researchers, because it attaches to the muscular (coronoid) process of the lower jaw – the mandible bone.

https://www.sciencedirect.com/science/article/pii/S0940960221002053

https://www.sciencealert.com/scientists-just-identified-a-new-muscl...

Comment by Dr. Krishna Kumari Challa on December 23, 2021 at 10:51am

Researchers identify mechanism that explains how tissues form complex shapes that enable organ function

Our bodies are made of tissues arranged in complex shapes that aid in performing specific functions.

But how do cells fold themselves so precisely into such complicated configurations during development? What are the fundamental forces driving this process?

Now, researchers at Harvard Medical School have discovered a mechanical process by which sheets of cells morph into the delicate, looping semicircular canals of the inner ear.

The research reveals that the process involves a combination of hyaluronic acid, produced by cells, that swells with water, and thin connectors between cells that direct the force of this swelling to shape the tissue.

The conventional thinking is that the proteins actin and myosin act as tiny motors inside cells, pushing and pulling them in different directions to fold a tissue into a specific shape. However, the researchers discovered that zebrafish semicircular canals form through a markedly different process. During development, the cells produce hyaluronic acid, which is perhaps most well known as an antiwrinkle agent in beauty products. Once in the extracellular matrix the acid swells up, not unlike a diaper in a swimming pool. This swelling creates enough force to physically move nearby cells, but since the pressure is the same in all directions, the researchers wondered how the tissue ends up stretching in one direction and not another to form an elongated shape. The team found that this is accomplished by thin connectors between cells—dubbed cytocinches—that constrain the force.

It's like if you were to put a corset on a water balloon and deform it into an oblong structure. This combination of swelling and cinching progressively shapes an initially flat sheet of cells into tubes.

Although conducted in zebrafish, the work reveals a basic mechanism for how tissues take on shapes—one that is likely to be conserved across vertebrates, the researchers say, and may also have implications for bioengineering.

The genes that control hyaluronic acid production in zebrafish semicircular canals are also present in the semicircular canals  of mammals, suggesting that a similar process may be occurring. Moreover, hyaluronic acid is found in multiple parts of the human body, including skin and joints, indicating that it may play a role in shaping many tissues and organs—an avenue for future research.

If that does turn out to be the case, then studying the genes involved in hyaluronic acid production could help researchers understand congenital defects in organs where hyaluronic acid drives development.

Sean G. Megason, Extracellular hyaluronate pressure shaped by cellular tethers drives tissue morphogenesis, Cell (2021). DOI: 10.1016/j.cell.2021.11.025. www.cell.com/cell/fulltext/S0092-8674(21)01373-8

https://phys.org/news/2021-12-mechanism-tissues-complex-enable-func...

Comment by Dr. Krishna Kumari Challa on December 23, 2021 at 9:28am

Fire and Ice: The Puzzling Link Between Western Wildfires & Arctic Sea Ice

Comment by Dr. Krishna Kumari Challa on December 22, 2021 at 11:44am

Hubble and Webb: A New Golden Age of Astronomy

Comment by Dr. Krishna Kumari Challa on December 22, 2021 at 11:39am

The UV index takes into account how much UV radiation of different wavelengths is around and how each of those wavelengths affects our skin.

ARPANSA has a network of sensors around Australia measuring sunlight at different wavelengths to determine the UV index, with the information available online in real time.

This data is combined with other information about location, cloud cover and atmospheric conditions to produce maps and forecasts of the UV index for the whole country.

The UV index you see reported is usually the daily maximum—that's the highest it will be all day.

How high it gets depends on lots of factors, including your location, the time of year, the amount of cloud cover, and ozone and pollution in the atmosphere.

The index tends to be higher closer to the Equator and at high altitudes, as the sunlight has to pass through less air before it reaches the ground.

https://theconversation.com/what-is-the-uv-index-an-expert-explains...

Part 2

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Comment by Dr. Krishna Kumari Challa on December 22, 2021 at 11:38am

What is the UV index? 

You've probably seen the UV index in the day's weather forecast, and you know it tells you when you need to cover up and wear sunscreen.

The Sun showers Earth with light at a huge spectrum of different wavelengths, and each wavelength can have a slightly different effect on human skin.

An important part of the spectrum is ultraviolet or UV radiation: light with wavelengths too short for our eyes to see, from around 400 nanometres to 10 nanometres.

There are two important kinds of UV radiation: UV-A, with wavelengths from 400–315 nanometres, and UV-B with wavelengths from 315–280 nanometres. (Shorter wavelengths are called UV-C, but are mainly blocked by the atmosphere so we don't need to worry about it.)

UV-A and UV-B both contribute to skin damage, aging and skin cancer. But UV-B is the more dangerous: it is the major cause of sunburn, cataracts and skin cancer.

The UV index tells you how much ultraviolet radiation is around at ground level on a given day, and its potential to harm your skin.

UV radiation is a component of sunlight that can cause tanning and sunburn in the short term. In the longer term, too much exposure to UV can cause cataracts and skin cancer.

In 2002, the World Health Organization devised the UV index in an effort to make people around the world more aware of the risks.

The index boils down several factors into a single number that gives you an idea of how careful you need to be in the sun. A score of 1 or 2 is low, 3–5 is moderate, 6 or 7 is high, 8–10 is very high, and 11 and above is extreme.

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