Connect with us

Science

Iron hydroxide forms more easily on mineral surfaces than previously thought – MINING.com

Published

 on


Knowing the exact moment when iron hydroxide forms on quartz substrates can support water quality processes at acid mine drainage sites

Nucleation and growth together are known as precipitation — and their sum has been used to predict iron hydroxide’s formation behaviour. But these predictions have largely omitted separate consideration of nucleation.

In Jun’s view, this means that previous results were not accurate enough.

“Our work provides an empirical, quantitative description of nucleation, not a computation, so we can provide scientific evidence about this missing link,” the researcher said.

By using X-rays and a novel experimental cell she developed to study environmentally relevant complex systems with plenty of water, ions and substrate material, Jun was able to observe nucleation in real-time.

The work consisted of employing an X-ray scattering technique called “grazing-incidence small-angle X-ray scattering.” By shining X-rays onto a substrate with a very shallow angle, close to the critical angle that allows total reflection of light, this technique can detect the first appearance of nanometer size particles on a surface.

The empirical measuring of the initial point of nucleation revealed that the general estimates scientists have been using overstate the amount of energy needed for this process.

“Iron hydroxide forms much more easily on mineral surfaces than scientists thought because less energy is needed for nucleation of highly hydrated solids on surfaces,” Jun said.

According to the scientist, her findings can help better understand processes related to water quality at acid mine drainage sites, the reduction of membrane fouling and pipeline scale formation, and the developing of more environmentally friendly superconductor materials.

Let’s block ads! (Why?)



Source link

Continue Reading

Science

NASA's 8-Minute Rocket Test Shuts Down After 67 Seconds – KCCU

Published

 on


NASA has more work to do, after a rocket test Saturday for its shuttle replacement ended with a premature and unexpected shutdown.

The test, at NASA’s Stennis Space Center in Mississippi, was part of NASA’s Artemis program, a plan to return to the moon in the coming years. NASA’s test called for four engines to fire for eight minutes — roughly the time it will take for NASA’s long-delayed Space Launch System (SLS) to generate the thrust needed to send the rocket to space.

But the engines shut down after just 67 seconds, when engine number 4 suffered a “major component failure.” Scientists aren’t yet sure what caused the early shutdown, but they plan to analyze and regroup.

“Saturday’s test was an important step forward to ensure that the core stage of the SLS rocket is ready for the Artemis I mission, and to carry crew on future missions,” said NASA Administrator Jim Bridenstine, who attended the test.

“Although the engines did not fire for the full duration, the team successfully worked through the countdown, ignited the engines, and gained valuable data to inform our path forward,” he said.

The engines NASA tested are the same ones that would be used to eventually launch the Orion space capsule to the moon. So scientists have to be careful with them.

“The amount of risk that we can take is very, very low,” Bridenstine said. “We can’t afford to have this vehicle fail. And guess what? Because we have done all the work that we have done, this article made the right decision to shut itself down.”

Now NASA has to figure out what caused the component failure that led to the shutdown. If scientists conduct another test, it will take at least 3-4 weeks to prepare the engines, the agency said.

NASA announced the SLS about 10 years ago, as a successor to the retired Space Shuttle program. It’s a rocket and capsule combo that, when complete, will enable deep space missions. NASA hopes to have astronauts on the moon in 2024, and eventually Mars and beyond.

Copyright 2021 NPR. To see more, visit https://www.npr.org.

Let’s block ads! (Why?)



Source link

Continue Reading

Science

How to literally drive the coronavirus away – Deccan Herald

Published

 on


Over the past year, as health authorities have tried to curb the Covid-19 pandemic, researchers have trained their scientific attention on a variety of potentially risky environments: places where large groups of people gather and the novel coronavirus has ample opportunity to spread. They have swabbed surfaces on cruise ships, tracked case numbers in gyms, sampled ventilation units in hospitals, mapped seating arrangements in restaurants and modeled boarding procedures in airplanes.

They have paid less attention to another everyday environment: the car. A typical car, of course, does not carry nearly enough people to host a traditional superspreader event. But cars come with risks of their own; they are small, tightly sealed spaces that make social distancing impossible and trap the tiny, airborne particles, or aerosols, that can transmit the coronavirus.

“Even if you’re wearing a face covering, you still get tiny aerosols that are released every time you breathe,” said Varghese Mathai, a physicist at the University of Massachusetts, Amherst. “And if it’s a confined cabin, then you keep releasing these tiny particles, and they naturally would build up over time.”

Read: Decoding how airflow inside car may affect Covid-19 transmission risk

In a new study, Mathai and three colleagues at Brown University — Asimanshu Das, Jeffrey Bailey and Kenneth Breuer — used computer simulations to map how virus-laden airborne particles might flow through the inside of a car. Their results, published in early January in Science Advances, suggest that opening certain windows can create air currents that could help keep both riders and drivers safe from infectious diseases like Covid-19.

To conduct the study, the research team employed what are known as computational fluid dynamic simulations. Engineers commonly use these kinds of computer simulations, which model how gases or liquids move, to create race cars with lower drag, for instance, or airplanes with better lift.

The team simulated a car loosely based on a Toyota Prius driving at 50 mph with two occupants: a driver in the front left seat and a single passenger in the back right,  a seating arrangement that is common in taxis and ride shares and that maximizes social distancing. In their initial analysis, the researchers found that the way the air flows around the outside of the moving car creates a pressure gradient inside the car, with the air pressure in the front slightly lower than the air pressure in the back. As a result, air circulating inside the cabin tends to flow from the back of the car to the front.

Next, they modeled the interior air flow — and the movement of simulated aerosols — when different combinations of windows were open or closed. (The air conditioning was on in all scenarios.) Unsurprisingly, they found that the ventilation rate was lowest when all four windows were closed. In this scenario, roughly 8% to 10% of aerosols exhaled by one of the car’s occupants could reach the other person, the simulation suggested. When all the windows were completely open, on the other hand, ventilation rates soared, and the influx of fresh air flushed many of the airborne particles out of the car; just 0.2% to 2% of the simulated aerosols traveled between driver and passenger.

The results jibe with public health guidelines that recommend opening windows to reduce the spread of the novel coronavirus in enclosed spaces. “It’s essentially bringing the outdoors inside, and we know that the risk outdoors is very low,” said Joseph Allen, a ventilation expert at the Harvard T.H. Chan School of Public Health. In an op-ed last year, he highlighted the danger that cars could pose for coronavirus transmission, and the potential benefits of opening the windows. “When you have that much turnover of air, the residence time, or how much time the aerosols stay inside the cabin, is very short,” Allen said

Because it is not always practical to have all the windows wide open, especially in the depths of winter, Mathai and his colleagues also modeled several other options. They found that while the most intuitive-seeming solution — having the driver and the passenger each roll down their own windows — was better than keeping all the windows closed, an even better strategy was to open the windows that are opposite each occupant. That configuration allows fresh air to flow in through the back left window and out through the front right window and helps create a barrier between the driver and the passenger.

“It’s like an air curtain,” Mathai said. “It flushes out all the air that’s released by the passenger, and it also creates a strong wind region in between the driver and the passenger.”

Richard Corsi, an air quality expert at Portland State University, praised the new study. “It’s pretty sophisticated, what they did,” he said, although he cautioned that changing the number of passengers in the car or the driving speed could affect the results.

Read | Consumers prioritising car ownership post-coronavirus lockdown, 74% want own vehicle: Survey

Corsi, a co-author of the op-ed with Allen last year, has since developed his own model of the inhalation of coronavirus aerosols in various situations. His results, which have not yet been published, suggest that a 20-minute car ride with someone who is emitting infectious coronavirus particles can be much riskier than sharing a classroom or a restaurant with that person for more than an hour.

“The focus has been on superspreader events” because they involve a lot of people, he said. “But I think what sometimes people miss is that superspreader events are started by somebody who’s infected who comes to that event, and we don’t speak often enough about where that person got infected.”

In a follow-up study, which has not yet been published, Mathai found that opening the windows halfway seemed to provide about the same benefit as opening them fully, while cracking them just one-quarter of the way open was less effective.

Mathai said that the general findings would most likely hold for many four-door, five-seat cars, not just the Prius. “For minivans and pickups, I would still say that opening all windows or opening at least two windows can be beneficial,” he said. “Beyond that, I would be extrapolating too much.”

Ride-sharing companies should be encouraging this research, Mathai said. He sent a copy of his study to Uber and Lyft, he said, but has not received a response.

Let’s block ads! (Why?)



Source link

Continue Reading

Science

The Olduvai Gorge gives up two-million-year-old secrets – Varsity

Published

 on


Few archaeological sites can claim to be famous, but the Olduvai Gorge in northern Tanzania is chief among them. With the word ‘olduvai’ coming from a misspelling of the Maasai word, ‘oldupai,’ a name for a plant that grows in the area, the fossil-rich region is famous for offering up some of the first evidence of fossil remains and stone tools used by early hominins, ancestors of today’s humans.

In the 1930s, Louis and Mary Leakey were working in Olduvai when they uncovered stone tools from early humans. Since then, it has become a popular archaeological site. The gorge lent an even older name — the Oldoway Gorge — to the paleolithic culture discovered there before the Abbevillian culture and, subsequently, their tools. Oldowan tools are often either large hammering stones or smaller, sharper flake stones used for cutting. They were used by precursors to modern Homo sapiens, such as Homo habilis.

Now, an international research team comprised of scientists from around the world, including from U of T, have conducted a thorough search of the Olduvai Gorge and concluded that hominins were living and building tools in the site as early as two million years ago. Moreover, their continual occupation of the gorge, extending over a 235,000-year period, shows how early hominins could adapt to changing environments — a skill that might have aided in their expansion out of Eastern Africa.

A wide source of information

The researchers combed through a wide array of sources to reach their findings. They took samples from previously excavated fossils and tools and compared them against samples of pollen, plants, and charcoal from wildfires, which were all deposited into the soil millions of years ago. The result was a pattern of human activity in the same place across time.

The prehistoric Olduvai landscape contained a variety of environments, such as streams, floodplains, woody forest, dry steppe, and even patches of land covered by ash from volcanic activity. Early hominins were able to exploit all of these environments, partly by bringing materials they needed for tools with them. Some of the rocks used to make tools originated 12 kilometres from where they were found. Others were made using what was at hand.

However, it is not clear which hominin species made these tools, largely because no new fossils were found. One possible candidate is Homo habilis because their fossils have been excavated nearby.

Rethinking the past

Oldowan tools have been excavated in nearby Ethiopia dating back to 2.6 million years ago, so this study does not represent the earliest discovery of stone tools. But it does extend the timeline of the Olduvai Gorge specifically. Previously, the oldest use of tools in the region was dated to 1.85 million years ago, so these findings push that start point by about 150,000 years. 

Moreover, these new findings demonstrate that early hominins had a robust ability to adapt to new environments. Julio Mercader Florin, lead author and professor at the University of Calgary, wrote in The Conversation that “This is a clear sign that 2 million years ago humans were not constrained technologically and already had the capacity to expand geographic range.”

The researchers discovered that the tools used remained the same regardless of what environment they were found in. It might have been human adaptability, then, that enabled our ancestors to thrive in the Olduvai Gorge and beyond.

Let’s block ads! (Why?)



Source link

Continue Reading

Trending