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Comment by Dr. Krishna Kumari Challa on October 10, 2021 at 1:10pm

The adult forms of the teeth we use to grind our food into a paste typically emerge from our gums in three stages – at around 6, 12, and 18 years of age (give or take).

Other primates get their adult molars earlier. For all our similarities in growth stages, the chimpanzee (Pan troglodytes) gets their molars at 3, 6, and 12. The yellow baboon (Papio cynocephalus) has its last adult molars out by age seven, and the rhesus macaque (Macaca mulatta) is all done by the time they're six.

One important factor constraining the timing of when teeth can appear is space. If the jaw isn't big enough for an adult-sized dental set, there's no point in squeezing them in.

Humans don't exactly have a lot of mouth space as it is, with impacted wisdom teeth a major problem for our species. But this doesn't explain why they pop up so late in our lives, or why the very back ones seem to be increasingly causing trouble.

Having an empty space for a tooth to grow doesn't make it a good idea to put one there, though. Teeth don't crunch all on their own – there's a whole lot of muscles and bone supporting them, ensuring sufficient pressure can safely tear and grind up our food.

"This study provides a powerful new lens through which the long-known linkages among dental development, skull growth and maturational profiles.

https://www.sciencealert.com/we-now-know-why-we-don-t-get-our-wisdo...

part2

Comment by Dr. Krishna Kumari Challa on October 10, 2021 at 1:09pm

Scientists Finally Know Why Wisdom Teeth Only Emerge When We're Basically Adults

Homo sapiens don't grow their last few teeth until they're nearly out of the teenage years.

This mystery of the molars is a tricky one to solve, in spite of their emergence playing such a critical role in tracking shifts in our evolution. But researchers  now think they might have cracked it.

One of the mysteries of human biological development is how the precise synchrony between molar emergence and life history came about and how it is regulated. Turning the bones and teeth of 21 species of primate into 3D models, the researchers were able to work out that the timing of our adult molars has a lot to do with the delicate balance of biomechanics in our growing skulls.  

And it's 'safety' that seems to be behind our tardy tooth growth.

"It turns out that our jaws grow very slowly, likely due to our overall slow life histories and, in combination with our short faces, delays when a mechanically safe space – or a 'sweet spot,' if you will – is available, resulting in our very late ages at molar emergence.

The back molars in primates sit just in front of two temporomandibular joints, which together form a hinge between your jaw and the skull. Unlike other joints in our body, the two pivots have to operate in perfect sync with one another. They also need to transfer a fair degree of force onto one or more points to get you biting and chewing.

In biomechanics, this three-point-process is governed by principles within something called the constrained level model. Put a tooth in the wrong spot, and the forces produced under this model could be bad news for a jaw that simply isn't big enough to cope.

For species with longer jaws, the time it takes for the skull to develop a suitable structure for teeth closest to the muscles near the hinge is relatively brief.

Humans, with our significantly flatter faces, have no such luck, needing to wait until our skulls have developed to a point that the forces put on each set of adult molars won't damage our growing jaw.

Not only does this give us a new way to evaluate dental conditions, such as impacted molars, but it could help paleontologists to better understand the evolution of our unique jaws among our hominid ancestors.

https://www.science.org/doi/10.1126/sciadv.abj0335

Part 1

Comment by Dr. Krishna Kumari Challa on October 9, 2021 at 11:47am

The thin line between science and pseudo-science

Comment by Dr. Krishna Kumari Challa on October 9, 2021 at 9:35am

Why fast charging reduces the capacity of a car battery

When lithium ions are forced rapidly through a battery, they might get stuck and turn into lithium metal, no longer able to move through the battery.

Fast charging is kind of the Holy Grail. It is what everyone who owns a lithium ion battery based device wants to be able to do.

Inside the battery, however, there is a lot of complicated chemistry that can be sensitive to how fast it is charged. Things can go wrong. Capacity loss is the most critical one.

It is possible to make batteries with very high capacity that might allow you to drive your electric car 1000 km, but after you've charged and discharged it a few times, you would lose about half of that capacity and range.

All rechargeable batteries deteriorate over time, but this negative effect is extra strong when the battery is subjected to fast charging. They have been able to see that the lithium ions, which are so important for the capacity of a battery, are converted into pure lithium metal and are no longer useful. And most importantly: this effect is greatly enhanced by fast charging.

During fast charging, the same number of ions move through the system, but much faster. All ions must find their place in the anode in a much shorter time.

When you charge at double speed, you have to move the same amount of ions and electrons in half the time. The most likely thing is you get these lithium ions building up and they just can't get to the graphite anymore. They get stuck there and there's a lot of heat, a lot of energy being put into them, and so they get reduced to lithium metal.

 Donal P. Finegan et al, Spatial dynamics of lithiation and lithium plating during high-rate operation of graphite electrodes, Energy & Environmental Science (2020). DOI: 10.1039/d0ee01191f

https://techxplore.com/news/2021-10-fast-capacity-car-battery.html?...

Comment by Dr. Krishna Kumari Challa on October 9, 2021 at 9:19am

Why do ducks move in a row in water?

Riding the waves keeps ducks in a row

The sight of ducklings paddling in a line behind their mother is a common sight in rivers and ponds.

 

But just why do they swim in that formation? Scientists think they have discovered the reason—which could have applications in maritime shipping too.

In a research paper published in the Journal of Fluid Mechanics, naval architecture experts conclude that ducklings benefit from 'wave riding' and 'wave passing."

Using a mathematical and numerical model, the researchers found that when a duckling swims at a 'sweet point' behind its mother a 'destructive wave interference phenomenon' occurs. This causes the wave drag of the duckling to turn positive meaning the baby bird is actually pushed forward by the wave.

Interestingly this wave-riding benefit appears to be passed down to the rest of the ducklings in the line formation. Starting from the third duckling the wave drag of individuals gradually tends towards zero, and a delicate dynamic equilibrium is achieved. Each individual under that equilibrium acts as a wave passer, passing the waves' energy to its trailing companion without any energy losses.

Wave riding and wave passing are probably the principal reasons for the evolution of swimming formation by waterfowl.

This study is the first to reveal the reasons why the formation movement of waterfowl can preserve individuals' energy expenditure.

These principles could be potentially applied to design modern freight carrying vessels, e.g. a water-train, to transport more cargoes without extra fuel cost.

Zhi-Ming Yuan et al, Wave-riding and wave-passing by ducklings in formation swimming, Journal of Fluid Mechanics (2021). DOI: 10.1017/jfm.2021.820

https://phys.org/news/2021-10-ducks-row.html?utm_source=nwletter&am...

Comment by Dr. Krishna Kumari Challa on October 7, 2021 at 11:52am

Emerging infectious disease caused by a tick-borne nairovirus identified in Japan

A previously unknown virus that can infect humans and cause disease has been identified by scientists in Japan. The novel infectious virus, named Yezo virus, is transmitted by tick bites and causes a disease characterized by fever and a reduction in blood platelets and leucocytes. The discovery was made by researchers at Hokkaido University  and the results have been published in the journal Nature Communications.

At least seven people have been infected with this new virus in Japan since 2014, but, so far, no deaths have been confirmed. The Yezo virus was discovered after a 41-year-old man was admitted to the hospital in 2019 with fever and leg pain after being bitten by an arthropod believed to be a tick while he was walking in a local forest in Hokkaido. He was treated and discharged after two weeks, but tests showed he had not been infected with any known viruses carried by ticks in the region. A second patient showed up with similar symptoms after a tick bite the following year.

Genetic analysis of viruses isolated from blood samples of the two patients found a new type of orthonairovirus, a class of nairovirus, that includes pathogens such as the Crimean-Congo haemorrhagic fever virus. The scientists named it Yezo virus, after a historical Japanese name for Hokkaido, a large island in the north of the country where the virus was discovered. The novel virus was found most closely related to Sulina virus and Tamdy virus, detected in Romania and Uzbekistan, respectively, the latter of which reportedly caused acute fever in humans recently in China.

The scientists then checked blood samples collected from hospital patients who showed similar symptoms after tick bites since 2014. They found additional positive samples from five patients. These patients, including the first two, had a fever and reduced blood platelets and leucocytes, and showed indicators of abnormal liver function.

To determine the likely source of the virus, the research team screened samples collected from wild animals in the area between 2010 and 2020. They found antibodies for the virus in Hokkaido shika deer and raccoons. They also found the virus RNA in three major species of ticks in Hokkaido. The Yezo virus seems to have established its distribution in Hokkaido, and it is highly likely that the virus causes the illness when it is transmitted to humans from animals via ticks.

1. Fumihiro Kodama, Hiroki Yamaguchi, Eunsil Park, Kango Tatemoto, Mariko Sashika, Ryo Nakao, Yurino Terauchi, Keita Mizuma, Yasuko Orba, Hiroaki Kariwa, Katsuro Hagiwara, Katsunori Okazaki, Akiko Goto, Rika Komagome, Masahiro Miyoshi, Takuya Ito, Kimiaki Yamano, Kentaro Yoshii, Chiaki Funaki, Mariko Ishizuka, Asako Shigeno, Yukari Itakura, Lesley Bell-Sakyi, Shunji Edagawa, Atsushi Nagasaka, Yoshihiro Sakoda, Hirofumi Sawa, Ken Maeda, Masayuki Saijo, Keita Matsuno. A novel nairovirus associated with acute febrile illness in Hokkaido, Japan. Nature Communications, 2021; 12 (1) DOI: 10.1038/s41467-021-25857-0

https://www.sciencedaily.com/releases/2021/10/211004104237.htm

Comment by Dr. Krishna Kumari Challa on October 7, 2021 at 11:48am

Clinical Trial Testing Automatic Oxygen Control Device for Premature Infants

The consequences are dire for the health of a premature baby — too much oxygen can cause blindness, and too little oxygen can cause brain damage and other negative health effects. Some premature babies need the help of life-saving machines in a neonatal intensive care unit, or NICU, to provide oxygen that eases the struggle to take their first breaths. However, small, personalized adjustments — to either raise or lower the level of oxygen provided — must be made by hand under the careful attention of nurses and respiratory therapists. Now, a clinical trial will test a new device that could make those needed adjustments for premature babies in a NICU — automatically.

Comment by Dr. Krishna Kumari Challa on October 7, 2021 at 9:30am

How 'ice needles' weave patterns of stones in frozen landscapes

Nature is full of repeating patterns that are part of the beauty of our world. An international team, including a researcher from the University of Washington, used modern tools to explain repeating patterns of stones that form in cold landscapes.

The new study, published Oct. 5 in the Proceedings of the National Academy of Sciences, uses experimental tools to show how needles of ice growing randomly on frozen ground can gradually move rocks into regular, repeating patterns. The team, based mainly in China and Japan, uses a combination of novel experiments and computer modeling to describe these striking features with new theoretical insights.

"The presence of these amazing patterns that develop without any intervention from humans is pretty striking in nature.

One of the reasons for the patterns is needle ice. As the temperature drops, the moisture contained in the soil grows into spikes of ice crystals that protrude from the ground.

"When you go out in the backyard after a freezing night and you feel a little crunch under the foot, you're probably walking on needle ice.

As needle ice forms it tends to push up soil particles, and if there are any, small stones. More needle ice can form on patches of bare soil compared to rock-covered areas. The ice needles will slightly displace any remaining stones in the barer region. Over years, the stones begin to cluster in groups, leaving the bare patches essentially stone-free.

That kind of selective growth involves interesting feedbacks between the size of the stones, the moisture in the soil and the growth of the ice needles.

Watch a video that shows how this happens here:

https://movie-usa.glencoesoftware.com/video/10.1073/pnas.2110670118...

Anyuan Li et al, Ice needles weave patterns of stones in freezing landscapes, Proceedings of the National Academy of Sciences (2021). DOI: 10.1073/pnas.2110670118

https://www.washington.edu/news/2021/10/06/how-ice-needles-weave-pa...

Comment by Dr. Krishna Kumari Challa on October 7, 2021 at 9:05am

Second, fallout from biomass burning is rich in micronutrients such as iron. Phytoplankton growth in much of the Southern Ocean is nutrient-limited so the increased fallout from Māori burning probably resulted in centuries of enhanced phytoplankton growth in large areas of the Southern Hemisphere.

Third, the results refine what is known about the timing of the arrival of the Māori in New Zealand, one of the last habitable places on earth to be colonized by humans. Māori arrival dates based on radiocarbon dates vary from the 13^th to 14^th century, but the more precise dating made possible by the ice core records pinpoints the start of large scale burning by early Māori in New Zealand to 1297, with an uncertainty of 30 years.

"From this study and other previous work this team has done such as on 2,000-year old lead pollution in the Arctic from ancient Rome, it is clear that ice core records are very valuable for learning about past human impacts on the environment. "Even the most remote parts of Earth were not necessarily pristine in preindustrial times."

Hemispheric black carbon increase after the 13th-century Māori arrival in New Zealand, Nature (2021). DOI: 10.1038/s41586-021-03858-9

https://phys.org/news/2021-10-early-human-impacted-earth-atmosphere...

Part 3

Comment by Dr. Krishna Kumari Challa on October 7, 2021 at 9:04am

After consulting paleofire records from each of the three regions, only one viable possibility remained: New Zealand, where charcoal records showed a major increase in fire activity beginning about the year 1300. This date also coincided with the estimated arrival, colonization, and subsequent burning of much of New Zealand's forested areas by the Māori people.

This was a surprising conclusion, given New Zealand's relatively small land area and the distance (nearly 4,500 miles), that smoke would have travelled to reach the ice core site on James Ross Island.

"Compared to natural burning in places like the Amazon, or Southern Africa, or Australia, you wouldn't expect Māori burning in New Zealand to have a big impact, but it does over the Southern Ocean and the Antarctic Peninsula

--

The study findings are important for a number of reasons. First, the results have important implications for our understanding of Earth's atmosphere and climate. Modern climate models rely on accurate information about past climate to make projections for the future, especially on emissions and concentrations of light-absorbing black carbon linked to Earth's radiative balance. Although it is often assumed that human impacts during preindustrial times were negligible compared to background or natural burning, this study provides new evidence that emissions from human-related burning have impacted Earth's atmosphere and possibly its climate far earlier, and at scales far larger, than previously imagined.

part2

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