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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.

Part 1

Comment by Dr. Krishna Kumari Challa on December 22, 2021 at 11:34am

No mountain is high enough for microplastics

From Mount Everest to the Mariana Trench, microplastics are everywhere—even high in the Earth's troposphere where wind speeds allow them to travel vast distances, a study showed recently. 

Microplastics are tiny fragments—measuring less than 5 millimeters—that come from packaging, clothing, vehicles and other sources and have been detected on land, in water and in the air.

Scientists sampled air 2,877 meters above sea level at the Pic du Midi Observatory in the French Pyrenees, a so-called "clean station" because of the limited influence exerted on it by the local climate and environment.

There they tested 10,000 cubic meters of air per week between June and October of 2017 and found all samples contained microplastics.

Using weather data they calculated the trajectories of different air masses preceding each sample and discovered sources as far away as North Africa and North America.

The study's main author Steve Allen of Dalhousie University in Canada told AFP that the particles were able to travel such distances because they were able to reach great altitudes.

The research also points to microplastic sources in the Mediterranean Sea and the Atlantic Ocean.

Once in the air or ocean, it is moving around and around in an indefinite cycle.

Steve Allen, Evidence of free tropospheric and long-range transport of microplastic at Pic du Midi Observatory, Nature Communications (2021). DOI: 10.1038/s41467-021-27454-7. www.nature.com/articles/s41467-021-27454-7

https://phys.org/news/2021-12-microplastic-pristine-pyrenees-mounta...

Comment by Dr. Krishna Kumari Challa on December 22, 2021 at 11:24am

The researchers modeled various scenarios in close detail, such as a situation where passengers in different seats were pronouncing a vowel for a few seconds. By creating detailed representation of the flow field and tracking every single droplet, they were able to reconstruct their ventilation paths.

In the future, the team will reproduce conditions that more closely represent the diverse human activity on public transport vehicles to help inform actions, design, and operation of future ventilation systems for safer environments.

"These high-resolution simulations were focused on public transportation vehicles, but they could be extended to commercial or residential buildings, health care facilities, offices, or schools.

"Numerical investigation of droplets in a cross-ventilated space with sitting passengers under asymptomatic virus transmission conditions" Physics of Fluids, DOI: 10.1063/5.0070625

https://phys.org/news/2021-12-seat-exposure-exhaled-droplets.html?u...

Part 3

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Comment by Dr. Krishna Kumari Challa on December 22, 2021 at 11:23am

When it comes to preventing risk of infection, this is precisely what makes it difficult to contain."

The researchers analyzed what happens when speech droplets are exhaled from a row of sitting passengers in a ventilated space, like those in public transportation vehicles. In some of these systems, air is injected at the top and extracted at the bottom through the vents near the window seats.

This generates an internal recirculation to enhance thermal comfort and remove contaminants, but the researchers were interested in whether certain seat positions affect the circulation adversely.

The team found droplets from the window seat rose more and invaded the space of other passengers to a lesser extent shortly after exhalation. Moreover, droplets released from the middle seat contaminated the aisle passengers more, indicating the downward flow of personal ventilation in aisle seats could move droplets down and increase the risk of infection.

Droplets released from the aisle were dragged down by the ventilation system immediately.

Part 2

Comment by Dr. Krishna Kumari Challa on December 22, 2021 at 11:23am

Your seat on public transportation determines level of exposure to exhaled droplets

The COVID-19 pandemic has revealed the urgency of understanding how public transportation ventilation systems transmit viruses and how exhaled droplets evolve in ventilated spaces. Researchers have wondered if those ventilation systems can be improved to mitigate virus transmission.

In Physics of Fluids, researchers at IBM Research Europe developed a model with an unprecedented level of detail and focused on conditions that are more characteristic of asymptomatic transmission. The multiphysics model involved air and droplet dynamics, heat transfer, evaporation, humidity, and effects of ventilation systems.

"By visualizing the droplets and the flow, you realize the number of physical phenomena taking place around us that go unnoticed, such as the complex interactions between natural body plumes, exhalation, and ventilation.

Part 1

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Comment by Dr. Krishna Kumari Challa on December 21, 2021 at 11:39am

Bacteriostatic antibiotics promote CRISPR-Cas adaptive immunity by enabling increased spacer acquisition, Cell Host Microbe, 2021.

https://phys.org/news/2021-12-closer-harnessing-viruses-bacteria-an...

Part 3

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