Comment

Comment by Dr. Krishna Kumari Challa on January 24, 2022 at 9:09am

The temperature differential the ice is uniquely creating across the water layer has changed what happens in the water itself, because now most of the heat from the hot plate has to go across the water to maintain that extreme differential. So only a tiny fraction of the energy can be used to produce vapor anymore.

The elevated temperature of 550 degrees Celsius for the icy Leidenfrost effect is practically important. Boiling water is optimally transporting heat away from the substrate, which is why you feel ample heat rising from a pot of water that is boiling, but not from a pot of water that is merely hot. This means that the difficulty in levitating ice is actually a good thing, as the larger temperature window for boiling will result in better heat transfer compared to using a liquid alone.

It is much harder to levitate the ice than it was to levitate the water droplet. Heat transfer plummets as soon as levitation begins, because when liquid levitates, it doesn't boil anymore. It's floating over the surface rather than touching, and touching is what causes it to boil the heat away. So, for heat transfer, levitation is terrible. Boiling is incredible.

Practical applications: 

Heat transfer comes most into play for cooling off things like computer servers or car engines. It requires a substance or mechanism that can move energy away from a hot surface, redistributing heat quickly to reduce the wear and tear on metal parts. In nuclear power plants, the application of ice to induce rapid cooling could become an easily-deployed emergency measure if power fails, or a regular practice for servicing power plant parts.

There are also potential applications for metallurgy. To produce alloys, it is necessary to quench the heat from metals that have been shaped in a narrow window of time, making the metal stronger and less brittle. If ice were applied, it would allow heat to be offloaded rapidly through the three water phases, quickly cooling the metal.

A  potential for applications in firefighting: You could imagine having a specially made hose that is spraying ice chips as opposed to a jet of water.

Physical Review Fluids, DOI: 10.1103/PhysRevFluids.00.004000

https://phys.org/news/2022-01-ice-discovery-18th-century-principle....

Part 2

**

Comment by Dr. Krishna Kumari Challa on January 24, 2022 at 9:06am

Using ice to boil water: Researcher makes heat transfer discovery that expands on 18th century principle

have made a discovery about the properties of water that could provide an exciting addendum to a phenomenon established over two centuries ago. The discovery also holds interesting possibilities for cooling devices and processes in industrial applications using only the basic properties of water. Their work was published on Jan. 21 in the journal Physical Review Fluids.

Water can exist in three phases: a frozen solid, a liquid, and a gas. When heat is applied to a frozen solid, it becomes a liquid. When applied to the liquid, it becomes vapour. This elementary principle is familiar to anyone who has observed a glass of iced tea on a hot day, or boiled a pot of  water.

When the heat source  is hot enough, the water's behaviour changes dramatically.

Awater droplet deposited onto an aluminum plate heated to 150 degrees Celsius (302 degrees Fahrenheit) or above will no longer boil. Instead, the vapor that forms when the droplet approaches the surface will become trapped beneath the droplet, creating a cushion that prevents the liquid from making direct contact with the surface. The trapped vapor causes the liquid to levitate, sliding around the heated surface like an air hockey puck. This phenomenon is known as the Leidenfrost effect, named for the German doctor and theologian who first described it in a 1751 publication.

This commonly accepted scientific principle applies to water as a liquid, floating on a bed of vapour. Could ice perform in the same way?

While trying to answer this Q, what the researchers observed was fascinating. Even when the aluminum was heated above 150 C, the ice did not levitate on vapor as liquid does. Researchers continued raising the temperature, observing the behaviour of the ice as the heat increased. What he found was that the threshold for levitation was dramatically higher: 550 C (1022 F) rather than 150 C. Up until that threshold, the meltwater beneath the ice continued to boil in direct contact with the surface, rather than exhibit the Leidenfrost effect.

What was going on underneath the ice that prolonged the boiling?

The answer turned out to be the temperature differential in the meltwater layer beneath the ice. The meltwater layer has two different extremes: Its bottom is boiling, which fixes the temperature at about 100 C, but its top is adhered to the remaining ice, which fixes it at about 0 C. Edalatpour's model revealed that the maintenance of this extreme temperature differential consumes most of the surface's heat, explaining why levitation was more difficult for ice.

Part 1

Comment by Dr. Krishna Kumari Challa on January 22, 2022 at 9:39am

These scientists are racing to beat Omicron

They  have been racing to piece together a picture of Omicron, a variant that differs drastically from its predecessors. What they’re learning could guide the development of new vaccines that offer protection against future pandemics. In the near-term, such vaccines could provide a fresh supply of shots for those still awaiting their first dose – roughly 40 percent of people on the planet.

https://www.eurekalert.org/news-releases/940888

--

This Cheap, Effective, Patent-Free COVID Vaccine Could Be a Global ...

Comment by Dr. Krishna Kumari Challa on January 22, 2022 at 9:24am

Now you know exactly what causes the northern lights, how do you optimize your chances of seeing it? Seek out dark skies far from cities and towns. The further north you can go the better but you don't need to be in the Arctic Circle. We see them from time to time in Scotland, and they've even been spotted in the north of England—although they're still better seen at higher latitudes.

Websites such as AuroraWatch UK can tell you when it's worth heading outside. And remember that while events on the Sun can give us a few days warning, these are indicative, not foolproof. Perhaps part of the magic lies in the fact that you need a little bit of luck to see the aurora in all its glory.

---

Explore further

North Pole solar eclipse excited auroras on the other side of the w...

---

Provided by The Conversation 

This article is republished from The Conversation under a Creative Commons license. Read the original article.

https://phys.org/news/2022-01-northern-particles-sun.html?utm_sourc...

Part 3 

**

Comment by Dr. Krishna Kumari Challa on January 22, 2022 at 9:24am

When solar wind plasma arrives at the earth it interacts with the planet's magnetic field (as illustrated below—the magnetic field is represented by the lines that look a bit like a spider). Most of the time, plasma travels easily along the lines of the magnetic field, but not across them. This means that solar wind arriving at Earth is diverted around the planet and kept away from the Earth's atmosphere. In turn, the solar wind drags the field lines out into the elongated form seen on the night side, called the magnetotail.

Sometimes moving plasma brings magnetic fields from different regions together, causing a local breakdown in the pattern of magnetic field lines. This phenomenon, called magnetic reconnection, heralds a new magnetic configuration, and, importantly, unleashes a huge amount of energy.

These events happen fairly often in the Sun's outer atmosphere, causing an explosive energy release and pushing clouds of magnetized gas, called coronal mass ejections, away from the Sun (as seen in the image above).

If a coronal mass ejection arrives at Earth it can in turn trigger reconnection in the magnetotail, releasing energy that drives electrical currents in near-Earth space: the substorm. Strong electric fields that develop in this process accelerate electrons to high energies. Some of these electrons may have come from the solar wind, allowed into near-Earth space by reconnection, but their acceleration in the substorm is essential to their role in the aurora.

These particles are then funneled by the magnetic field towards the atmosphere high above the polar regions. There they collide with the oxygen and nitrogen atoms, exciting them to glow as the aurora.

Part 2

Comment by Dr. Krishna Kumari Challa on January 22, 2022 at 9:23am

Are the northern lights caused by 'particles from the Sun'? Not exactly

What a spectacle a big aurora is, its shimmering curtains and colorful rays of light illuminating a dark sky. Many people refer to aurora as the northern lights (the aurora borealis), but there are southern lights too (the aurora australis). Either way, if you're lucky enough to catch a glimpse of this phenomenon, it's something you won't soon forget.

The aurora is often explained simply as "particles from the Sun" hitting our atmosphere. But that's not technically accurate except in a few limited cases. So what does happen to create this natural marvel?

We see the aurora when energetic charged particles—electrons and sometimes ions—collide with atoms in the upper atmosphere. While the aurora often follows explosive events on the Sun, it's not quite true to say these energetic particles that cause the aurora come from the Sun.

Earth's magnetism, the force that directs the compass needle, dominates the motions of electrically charged particles in space around Earth. The magnetic field near the surface of Earth is normally steady, but its strength and direction fluctuate when there are displays of the aurora. These fluctuations are caused by what's called a magnetic substorm—a rapid disturbance in the magnetic field in near-Earth space.

To understand what happens to trigger a substorm, we first need to learn about plasma. Plasma is a gas in which a significant number of the atoms have been broken into ions and electrons. The gas of the uppermost regions of Earth's atmosphere is in the plasma state, as is the gas that makes up the Sun and other stars. A gas of plasma flows away continuously from the Sun: this is called the solar wind.

Plasma behaves differently from those gases we meet in everyday life. Wave a magnet around in your kitchen and nothing much happens. The air of the kitchen consists overwhelmingly of electrically neutral atoms, so it's quite undisturbed by the moving magnet. In a plasma, however, with its electrically charged particles, things are different. So if your house was filled with plasma, waving a magnet around would make the air move.

Part 1

Comment by Dr. Krishna Kumari Challa on January 21, 2022 at 11:33am

Pandemic preprints changed science forever The pandemic unleashed a staggering tide of preprint studies, which are released publicly before they have been peer reviewed. The stakes had never been higher, swift action was crucial and pre-printing results aided rapid data sharing, which expedited research. But it exposed the inner workings of the scientific process to a new audience and laid bare the best and worst of pandemic research. “We are down a pathway of open science, and that pathway is going to accelerate,” says physician-scientist Kyle Sheldrick. “Our choice is not whether it occurs or not; our choice is whether it occurs responsibly.”

Comment by Dr. Krishna Kumari Challa on January 21, 2022 at 9:50am

We're Facing a Myopia 'Epidemic', Scientists Say. Here's Why

Scientists are warning of an emerging 'epidemic' of myopia or near-sightedness, having observed sharp increases in the adult onset of myopia among late baby boomers.

Based on data collected from 107,442 participants in the extensive Biobank program in the UK, people born in the late 1960s are 10 percent more likely to be near-sighted than people born three decades earlier.

The biggest leap was in individuals who experienced their vision changes later in life, although among those with child-onset myopia, the number of severe cases doubled over the same period.

The condition is thought to be caused by a combination of genetic and environmental factors, including increased screen time – though the study also finds evidence that these are trends that can be changed with the right public health initiatives.

Digging further into the data, the researchers suggest several reasons for the jump: changes in the nutrition of diets in childhood, rises in the use of digital screens, and shifts in teaching methods (more homework and less time spent outdoors, for example).

An increase in the number of people staying in education past the age of 18 could also be a factor, according to the research. This association between higher education (more years spent reading, revising, and taking exams) and a higher risk of myopia has previously been noted in several previous studies.

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0...

https://www.sciencealert.com/we-re-facing-a-myopia-epidemic-scienti...

Comment by Dr. Krishna Kumari Challa on January 21, 2022 at 9:35am

In 2009, an international team of researchers put together a list of nine boundaries that kept our planet stable for human existence, including greenhouse gas emissions, the ozone layer, forests, and freshwater.

In 2015, they concluded humanity had breached four of these boundaries: climate change, greenhouse gas emissions, land-system change, and the extinction rate.

Until now, chemical pollution, or 'novel entities', had never been quantified.

Like a cap on greenhouse gases, researchers say nations also need to limit the rapid production of synthetic chemicals, while assessing the ones they've already got.

Today, tens of thousands of chemicals on the market are untested, and even the ones that have been assessed for health and safety still hold many unknown risks.

While some chemicals might be safe on their own, for instance, studies have shown they can grow toxic when breaking down or in the presence of other chemicals. If enough of these byproducts accumulate in the environment, it could potentially have long-lasting and detrimental impacts.

The chemicals in some sunscreens, for instance, have turned out to be toxic to coral. In recent years, antidepressants have also been found accumulating in water sources, where they appear to impact how some fish hunt for food.

Avoiding similar mistakes in the future will be all but impossible if we do not dramatically slow the global production of novel entities, and soon.

"Shifting to a circular economy is really important. That means changing materials and products so they can be reused not wasted, designing chemicals and products for recycling, and much better screening of chemicals for their safety and sustainability along their whole impact pathway in the Earth system."

https://pubs.acs.org/doi/10.1021/acs.est.1c04158

https://www.sciencealert.com/synthetic-chemicals-aren-t-just-pushin...

Part2

Comment by Dr. Krishna Kumari Challa on January 21, 2022 at 9:34am

We Have Breached The Safe Planetary Limit For Synthetic Chemicals, Scientists Warn

From sea to land to sky, Earth's systems are contaminated with synthetic substances, and scientists warn it has already pushed the integrity of our planet over the brink.

Today, there are about 350,000 human-made chemicals on the market, including plastics, pesticides, industrial chemicals, cosmetic chemicals, antibiotics, and other drugs.

The fact this number continues to rise at an extraordinary rate makes it virtually impossible for any authority to keep track of their potential impacts on the environment.

At this point, there's no keeping up. Now, a new analysis of the situation suggests we have firmly crossed a planetary boundary into an unsafe space.

Since the 1950s, chemical production has increased by 50-fold. By 2050, it's on track to triple again.

"The rate at which these pollutants are appearing in the environment far exceeds the capacity of governments to assess global and regional risks, let alone control any potential problems.

Even if we can slow chemical production in the future, novel entities of our own making have already infiltrated the atmosphere, the hydrosphere, the cryosphere, the geosphere, and the biosphere.

Given that many of these chemicals can live 'forever' in the environment, any potential threat they pose could be the foundation for ongoing problems far into the future.

Ignoring the problem is foolish, but that is largely what humanity has done.

Part1

• ‹ Previous
• 1
• …
• 527
• 528
• 529
• 530
• 531
• …
• 1080
• Next ›
• Page