Lab study of droplet dynamics advances 3-D printing

Lab study of droplet dynamics advances 3-D printing
A comparison between the experimentally observed ejected droplet shape at break-up (a) and the simulated droplet shape (b) at various operating conditions approaching the experimental conditions. The simulated droplet shape significantly differs from experiments, highlighting the fact that essential physics appear to be missing from the model. Credit: Andy Pascall/LLNL

A team of Lawrence Livermore National Laboratory (LLNL) scientists has simulated the droplet ejection process in an emerging metal 3-D printing technique called “Liquid Metal Jetting” (LMJ), a critical aspect to the continued advancement of liquid metal printing technologies.


In the paper, the team describes the simulating of metal droplets during LMJ, a novel process in which molten droplets of liquid metal are jetted from a nozzle to 3-D print a part in layers. The process does not require lasers or metal powder and is more similar to inkjet printing techniques.

Using the model, researchers studied the primary breakup dynamics of the metal droplets, essential to improving the understanding of LMJ. LMJ has advantages over powder-based approaches in that it provides a wider material set and does not require production or handling of potentially hazardous powders, researchers said. The journal Physics of Fluids published the study on Nov. 25, where it was chosen as an Editor’s Pick.

“We don’t currently have a good understanding of all of the physics that occur right when the droplet breaks off from the metal jet,” said co-author Andy Pascall. “This model points to additional physical mechanisms that might need to be considered to close the gap between experiments and modeling.”

To conduct the research, the team built a custom, liquid-metal printer capable of dispensing tin droplets. Combined with high-speed video, the printer served as an experimental test-bed for free-form, droplet-on-demand printing and allowed the team to track detailed droplet dynamics during the ejection process.

The video analysis enabled researchers to build a computational model to simulate the morphology of the metal droplets during ejection, revealing that the drops behave like an extruded “pill” with no tail formation.

The study demonstrates that while LMJ is highly stable and repeatable, it also is extremely challenging to model. In the future, the team plans to explore droplet ejection across a broader range of process parameters and seek greater understanding of the factors impacting droplet shape, breakup and satellite formation, including thermal effects, wettability and the role of surface oxides.


New model describing the deformation and breakup of droplets could help improve nanoscale printing and spraying


More information:
Victor A. Beck et al. A combined numerical and experimental study to elucidate primary breakup dynamics in liquid metal droplet-on-demand printing, Physics of Fluids (2020). DOI: 10.1063/5.0029438
Provided by
Lawrence Livermore National Laboratory

Citation:
Lab study of droplet dynamics advances 3-D printing (2020, December 4)
retrieved 4 December 2020
from https://phys.org/news/2020-12-lab-droplet-dynamics-advances-d.html

This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
part may be reproduced without the written permission. The content is provided for information purposes only.

Source

Read more

In Monterey Bay, California, scientists grab the chance to study white sharks up close

Growing over six meters (20 feet) long and armed with hundreds of serrated, razor-sharp teeth, white sharks are the world’s largest predatory fish.



a fish swimming under water


© Stanford University


In late summer and fall, up to 250 white sharks congregate in Monterey Bay, off the central Californian coast, to feast on marine mammals — including elephant seals and sea lions — that gather here to breed.

From a shark’s perspective, “think of Monterey Bay as having one of the best fast food restaurants on the planet,” says shark expert and Stanford professor, Barbara Block.

Block also travels to Monterey Bay because the annual marine mammal “buffet” offers her an ideal opportunity to study the sharks up close. She and her team lure the “curious” sharks alongside their small boat, attach electronic tags to their dorsal fins, and then track the sharks as they swim out to the open ocean and dive to depths of 2,000 meters (6,500 feet).

Data on white shark population sizes, life histories and migratory patterns, can be used to inform marine protection policy, says Block, adding that sharks play a vital role in maintaining ecological balance in the ocean. “We need these apex predators to keep our ecosystems healthy.”

Watch the video above to find out more.

Continue Reading

Source Article

Read more

China collects moon samples to study on Earth

“Chang’e has collected moon samples,” the agency said in a statement.

The probe, launched November 24 from the island of Hainan, is the latest venture by the space program that sent China’s first astronaut into orbit in 2003. Beijing also has a spacecraft headed to Mars and aims to land a human on the moon.

This week’s landing is “a historic step in China’s cooperation with the international community in the peaceful use of outer space,” said foreign ministry spokeswoman Hua Chunying.

“China will continue to promote international cooperation and the exploration and use of outer space in the spirit of working for the benefit of all mankind,” Hua said.

Plans call for the lander to spend two days drilling into the lunar surface and collecting 4.4 pounds of rocks and debris. The top stage of the probe will be launched back into lunar orbit to transfer the samples to a capsule to take back to Earth, where it is to land in China’s northern grasslands in mid-December.

If it succeeds, it will be the first time scientists have obtained fresh samples of lunar rocks since the Soviet Union’s Luna 24 probe in 1976.

The samples are expected to be made available to scientists from other nations, although it is unclear how much access NASA will have due to U.S. government restrictions on cooperation with China’s military-linked program.

From the rocks and debris, scientists hope to learn more about the moon, including its precise age, as well as increased knowledge about other bodies in our solar system. Collecting samples, including from asteroids, is an increasing focus of many space programs.

Chinese space program officials have said they envision future crewed missions along with robotic ones, including possibly a permanent research base. No timeline or other details have been announced.

Source Article

Read more

Continents prone to destruction in their infancy, study finds

Earth continents
Credit: Pixabay/CC0 Public Domain

Monash University geologists have shed new light on the early history of the Earth through their discovery that continents were weak and prone to destruction in their infancy.


Their research, which relies on mathematical modeling, is published today in Nature.

The Earth is our home and over its 4,500,000,000 (4.5 billion) year history has evolved to form the environment we live in and the resources on which we depend.

However, the early history of Earth, covering its first 1.5 billion years remains almost unknown and, consequently, poorly understood.

“This was the time of formation of the first continents, the emergence of land, the development of the early atmosphere, and the appearance of primordial life—all of which are the result of the dynamics of our planet’s interiors,” said lead study author ARC Future Fellow Dr. Fabio Capitanio from the Monash University School of Earth, Atmosphere and Environment.

“Reproducing the conditions of the early Earth in computer-generated numerical models, we show that the release of internal primordial heat, three to four times that of the present-day, caused large melting in the shallow mantle, which was then extruded as magma (molten rock) onto the Earth’s surface,” he said.

According to the researchers, the shallow mantle left behind by this process was dehydrated and rigid and formed the keels of the first continents.

“Our results explain that continents remained weak and prone to destruction in their infancy, ~4.5 to ~4.0 billion years ago, and then progressively differentiated and became rigid over the next billion years to form the core of our modern continents,” Dr. Capitanio said.

“The emergence of these rigid early continents resulted in their weathering and erosion, changing the composition of the atmosphere and providing nutrients to the ocean seeding the development of life.”

Dr. Capitanio specialises in investigating the dynamics of the Earth’s tectonics and plate motions to better understand the mechanisms that force single plates or whole-Earth changes.

The work adds to the knowledge on supercontinent formation and its fragmentation into the present-day continents.

The quantitative model used in the study explains the enigmatic melt degrees and layered structures observed in most cratons on Earth.

The process shows that continents remain weak and prone to destruction in their infancy, then progressively melt and differentiate to become stable continents.

This accounts for the transition from the Hadean, covering the first 500 million years of Earth history, in which crust was completely recycled, to the Archean (four to three billion years ago), when rigid continental keels built up and remain preserved through time.

“The geological record suggests that the very early continents did not survive and were recycled in the planet’s interiors, yet this trend dramatically inverted approximately four billion years ago, when the most enduring piece of continents, cratons, appeared,” Dr. Capitanio said.

Only tiny crystals remain from Earth’s earliest continental crust, formed more than 4 billion years ago. The mysterious disappearance of this crust can now be explained. The very process that formed new crust,

Read more

Entry barriers for women are amplified by AI in recruitment algorithms, study finds

businesswoman
Credit: Pixabay/CC0 Public Domain

Human gender biases that limit recruitment opportunities for women are mimicked and exacerbated by artificial intelligence (AI) used for sorting resumés, according to new research.


The study, commissioned by UniBank, analyzed how a panel of 40 human recruiters reacted when the exact same resumés were presented with male and female genders interchanged. The process was then applied to different hiring algorithms to see if the AI replicated human biases.

The research found the human recruiting panel demonstrated the strongest examples of unintentional bias, consistently preferring resumés of the male candidates over female equivalents.

Report co-author and gender policies researcher from the University’s Policy Lab, Associate Professor Leah Ruppanner said we know that more women than men have lost their job during the pandemic.

“Unfortunately, for data and finance roles, women’s resumés were ranked lower than men by our human panelists though they had the same qualifications and experience,” Professor Ruppanner said.

Report co-author and digital ethics researcher from the Center for AI and Digital Ethics (CAIDE), Dr. Marc Cheong said algorithms were then developed by the researchers to replicate the preferences of the human panel.

Credit: University of Melbourne

The research showed even basic algorithms could mimic subconscious human gender bias without taking into account the merits of a candidate.

“Even when the names of the candidates were removed, AI assessed resumés based on historic hiring patterns where preferences leaned towards male candidates. For example, giving advantage to candidates with years of continuous service would automatically disadvantage women who’ve taken time off work for caring responsibilities,” Dr. Cheong said.

“Also, in the case of more advanced AIs that operate within a “black box” without transparency or human oversight, there is a danger that any amount of initial bias will be amplified.”

UniBank General Manager, Mike Lanzing, said as the use of artificial intelligence becomes more common, it is important that to understand how existing biases are feeding into supposedly impartial models.

Credit: University of Melbourne

“We need to take care that we are not reversing decades of progress towards women’s financial independence and security by reinforcing outdated attitudes about the sort of work women are suited to,” Mr Lanzing said.

The report suggested a number of measures that could reduce bias in these processes including training programs for human resource professionals and creating transparent hiring algorithms designed to reduce gender bias.


Female bosses favour gay and lesbian job-seekers, research finds


Provided by
University of Melbourne

Citation:
Entry barriers for women are amplified by AI in recruitment algorithms, study finds (2020, December 2)
retrieved 2 December 2020
from https://phys.org/news/2020-12-entry-barriers-women-amplified-ai.html

This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
part may be reproduced without the written permission. The content is provided for information purposes only.

Source Article

Read more

Largest ever study of working parents finds Best Places to Work

Spoiler alert: Companies that provide better benefits and greater flexibility to working parents are seeing a return on their investment, according to Great Place to Work’s Annual Study of the Best Workplaces for Parents.

COVID-19 changed the way we work, perhaps for good. Remote working policies that focus on greater flexibility and different ways of measuring productivity have emerged since the pandemic forced many employers to reassess what it takes to engage workers. This is particularly true when it comes to measuring the contributions of working parents (particularly women), many of whom are juggling remote learning for their kids in addition to their own responsibilities.

Polling over 400,000 working parents, Great Place to Work’s data science team analyzed data from the workers who answered more than 60 questions on its Trust Index survey to come up with a list of current best employers for working parents. In addition to that, they measured written phrases and demographics to reveal why some parents experience a more positive work environment. The results make a strong business case for employers who support working parents. Among the highlighted findings from the report:

  • Companies that invest in employees and their families see 5.5 times more revenue growth thanks to greater innovation,
    higher talent retention, and increased productivity.
  • When working parents experience positive company culture, their organizations gain more than double the number of employees ready to innovate than their competitors which translates to revenue
  • When companies reduce burnout, their employees are 20x more likely to stay.
  • The Best Workplaces are thinking beyond maternity leave to provide benefits ranging from fertility coverage to return-to-work coaching to support finding child care.

Additionally, 93% of working men without children and 93% of working women without children who work for a company that invests in its working parent population say theirs is a great place to work. Eighty-nine percent of all workers at the best places for working parents say they want to remain there for a long time.

Source Article

Read more

To study aging, scientists are looking to outer space

As anyone who has experienced middle age will know, the process of growing old can be extremely hard on the body. Your bones begin to leak calcium, your muscles begin to shrivel, the immune system weakens, and arthritis can set in. Poor posture and balance affect how you move about the world, while cataracts and deteriorating eyesight impair how you see it. Heart problems and declining cognitive function eventually set in as people approach the end of their lives.



Mark Kelly in a blue shirt: Former NASA astronauts and identical twins Scott Kelly (right) and Mark Kelly. Scott spent a year on the ISS from 2015 to 2016 while Mark stayed on Earth, allowing scientists to study the effects of living in space on Scott's body and compare the changes to Mark.


© Photograph by ROBERT MARKOWITZ, NASA

Former NASA astronauts and identical twins Scott Kelly (right) and Mark Kelly. Scott spent a year on the ISS from 2015 to 2016 while Mark stayed on Earth, allowing scientists to study the effects of living in space on Scott’s body and compare the changes to Mark.


These symptoms, however, can also be caused by something less common: space travel.

Spaceflight influences biology in dramatic ways, and people in space appear to experience the effects of aging faster than people on Earth. Now, scientists have gained a better understanding of space travel’s influence on living beings than ever before. A slew of 29 papers recently published in the journals Cell, Cell Reports, iScience, Cell Systems, and Patterns examine the biological hazards of spaceflight in 56 astronauts—more than 10 percent of all the people who have ever been to space.



NASA astronauts Terry Virts (right) and Scott Kelly perform experiments for Rodent Research-2, a commercial investigation of the effects of spaceflight on the muscles, skeletons, and nervous systems of mice that were launched to the ISS on April 14, 2015.


© Photograph by NASA

NASA astronauts Terry Virts (right) and Scott Kelly perform experiments for Rodent Research-2, a commercial investigation of the effects of spaceflight on the muscles, skeletons, and nervous systems of mice that were launched to the ISS on April 14, 2015.


The new studies bring us a step closer to identifying the mechanisms underpinning the biological responses to living in space. More than 200 scientists demonstrated that space upends the genes, mitochondrial function, and chemical balances in the cells to trigger a cascade of broader health effects in spacefaring humans and animals.

Loading...

Load Error

“The entire body is affected, because [space] is such a different and extreme environment,” says Susan Bailey, a radiologist at Colorado State University who participated in multiple of the new studies.

The health effects associated with spaceflight have several similarities to aging-related disorders, such as cancer and osteoporosis. While spaceflight’s parallels to aging are a concern for long-term crewed missions—such as those that would be required on a voyage to Mars—the unique space environment also presents a unique opportunity to study the physiology of aging.



NASA’s Rodent Habitat, shown here with one of the two access doors open, provides long-term housing for rodents aboard the International Space Station.


© Photograph by Dominic Hart, NASA
NASA’s Rodent Habitat, shown here with one of the two access doors open, provides long-term housing for rodents aboard the International Space Station.

It’s estimated that the heart, blood vessels, bones, and muscles deteriorate more than 10 times faster in space than by natural aging. This means to study the aging process, scientists don’t have to wait for their biological subjects to naturally mature on Earth—they can harness the accelerated health effects by running experiments on the International Space Station (ISS).

Scientists stress that the symptoms of space

Read more

New study shows how methane breaks through icy barriers on the sea floor

new study shows how methan breaks through icy barriers on the sea floor
A new study has solved the mystery of how and why columns of the methane gas can stream out of methane hydrates. Both the bubble tubes and the inverted droplets are encased in clear gas hydrate. Credit: Image courtesy of the NOAA Office of Ocean Exploration and Research, Gulf of Mexico 2017.

Methane, the main component of natural gas, is the cleanest-burning of all the fossil fuels, but when emitted into the atmosphere it is a much more potent greenhouse gas than carbon dioxide. By some estimates, seafloor methane contained in frozen formations along the continental margins may equal or exceed the total amount of coal, oil, and gas in all other reservoirs worldwide. Yet, the way methane escapes from these deep formations is poorly understood.


In particular, scientists have been faced with a puzzle. Observations at sites around the world have shown vigorous columns of methane gas bubbling up from these formations in some places, yet the high pressure and low temperature of these deep-sea environments should create a solid frozen layer that would be expected to act as a kind of capstone, preventing gas from escaping. So how does the gas get out?

A new study helps explain how and why columns of the gas can stream out of these formations, known as methane hydrates. Using a combination of deep-sea observations, laboratory experiments, and computer modeling, researchers have found phenomena that explain and predict the way the gas breaks free from the icy grip of a frozen mix of water and methane. The findings are reported today in the journal PNAS, in a paper by Xiaojing (Ruby) Fu SM ’15, Ph.D. ’17, now at the University of California at Berkeley; Professor Ruben Juanes at MIT; and five others in Switzerland, Spain, New Mexico, and California.

Surprisingly, not only does the frozen hydrate formation fail to prevent methane gas from escaping into the ocean column, but in some cases it actually facilitates that escape.

Early on, Fu saw photos and videos showing plumes of methane, taken from a NOAA research ship in the Gulf of Mexico, revealing the process of bubble formation right at the seafloor. It was clear that the bubbles themselves often formed with a frozen crust around them, and would float upward with their icy shells like tiny helium balloons.

Later, Fu used sonar to detect similar bubble plumes from a research ship off the coast of Virginia. “This cruise alone detected thousands of these plumes,” says Fu, who led the research project while a graduate student and postdoc at MIT. “We could follow these methane bubbles encrusted by hydrate shells into the water column,” she says. “That’s when we first knew that hydrate forming on these gas interfaces can be a very common occurrence.”

But exactly what was going on beneath the seafloor to trigger the release of these bubbles remained unknown. Through a series of lab experiments and simulations, the mechanisms at work gradually became apparent.

Seismic studies of the subsurface of the

Read more

AMI Expeditionary Healthcare (AMI) Contracted by CDC to Study Spread of COVID-19 on University of Wisconsin Campuses

RESTON, Va., Dec. 1, 2020 /PRNewswire/ — AMI Expeditionary Healthcare (AMI) is contracted by Centers for Disease Control and Prevention (CDC) to determine the prevalence of asymptomatic COVID-19 carriers on college campuses and what can be done to slow the spread of the disease.

The CDC, based in Atlanta, GA, is contracting AMI to bolster COVID-19 testing sites to obtain blood samples of students from the Madison and Oshkosh campuses of the University of Wisconsin. The CDC will compare the new samples with samples taken at the beginning of Fall semester in September. The findings will help answer the question of how long antibodies stay present in the human body and whether these antibodies could protect individuals from reinfection.

About AMI 

AMI Expeditionary Healthcare is nationally and globally distributed. Physician-owned and physician-led, AMI has been providing healthcare solutions for over a decade in some of the most remote, challenging, and under-resourced environments in the world. AMI has delivered countless healthcare solutions and more than 7,000 medical personnel to upwards of 100 clinical and hospital settings on four continents. AMI is headquartered in Reston, VA.

If you would like to learn more about AMI and their services, please visit https://ami.health/

Facebook https://www.facebook.com/amiexpeditionaryhealthcare

LinkedIn https://www.linkedin.com/company/amiexpeditionaryhealthcare/

Twitter https://twitter.com/amiexphealth
Instagram https://www.instagram.com/ami.health/

*PHOTO: https://www.Send2Press.com/300dpi/20-1201s2p-ami-cdc-campus-300dpi.jpg

*Caption: AMI Expeditionary Healthcare (AMI) is contracted by Centers for Disease Control and Prevention (CDC) to determine the prevalence of asymptomatic COVID-19 carriers on college campuses and what can be done to slow the spread of the disease.

 

 

 

 

Cision View original content:https://www.prnewswire.com/news-releases/ami-expeditionary-healthcare-ami-contracted-by-cdc-to-study-spread-of-covid-19-on-university-of-wisconsin-campuses-301182170.html

SOURCE AMI Expeditionary Healthcare

Source Article

Read more

New Study Finds These Tropical Fish Can Live To Be Over 80 Years Old

How long do fish live? 10 years? Twenty? Try over 80 years, according to new research on snappers.

Before now, the oldest known snapper was recorded at 60 years old, two decades younger than findings recently published in the journal Coral Reefs. Does this twenty-year age gap matter? According to fisheries scientist and the study’s lead author Dr. Brett Taylor, it matters quite a bit.

Snappers serve as an important food source around the world. Despite the snapper’s importance, the global snapper fishery is, in large part, poorly managed. This, combined with the high market value of some snapper species, led the U.S. National Oceanic and Atmospheric Administration (NOAA) to officially label red snapper as ‘at risk’ for illegal, unreported, and unregulated (IUU) fishing and market fraud in 2015.

Snappers were known to be ‘long-lived’ species before the recent discovery of the 80-year-old fish. In fact, the snapper’s long lifespan is part of what makes the fish susceptible to exploitation. “There is a direct relationship between life span and how quickly a population can replenish itself through reproduction,” explains Taylor. “Long-lived marine fishes have evolved a strategy that allows them to buffer against periods of poor environmental conditions by having lots of mature, spawning individuals present in the populations. This strategy, however, did not evolve alongside the additional pressure of fishing, which directly removes these larger and older fish from the population.”

To better understand the effects of fishing – and potentially overfishing – on snappers, Taylor and his team studied three species of snappers that are not commercially or recreationally fished. “This allowed us to examine something more similar to ‘natural population structures’ that have not been truncated or otherwise affected by fishing pressure,” explains Taylor. With a lack of fishing pressure, knowledge of the age of these snapper species compared to commercially harvested species could provide important insights into the fishing’s effects on exploited snapper populations.

In addition to studying the age of the three snapper species, Taylor and his co-authors looked at whether snapper growth rates or life spans changed with different temperatures. In warm climates, cold-blooded animals like fish must use extra energy to compensate for their warm surroundings.

Before the widespread use of using fish ear stones (otoliths) to determine a fish’s age, in a manner not so different from counting rings inside a tree, scientists largely thought tropical fish were relatively short-lived species. “However, seminal research in the 1980s and 1990s showed us that many types of tropical reef fishes have extended life spans, way past what we previously presumed,” explains Taylor.

While Taylor’s research revealed

Read more