Researchers at the University of Illinois (UI) have honed a technique for handling tiny, soft particles using precisely controlled fluid flows that act as gentle microscopic hands, according to a news release posted on UI's website on Monday.
In three studies, UI researchers detail the technology and application of the Stokes trap, a method for manipulating small particles using only fluid flow. In the newest study, they used the Stokes trap to study the dynamics of vesicles, squishy fluid-filled particles that are stripped-down versions of cells and have direct relevance to biological systems.
"We found that when vesicles are deformed in a strong flow, they stretch into one of three distinct shapes - symmetric dumbbell, asymmetric dumbbell or ellipsoid shape," said Dinesh Kumar, a chemical and biomolecular engineering graduate student at UI. "We observed that these shape transitions are independent of the viscosity difference of the fluids between vesicle interior and exterior. This demonstrates that the Stokes trap is an effective way to measure stretching dynamics of soft materials in solution and far from equilibrium."
With new data, the researchers were able to produce a phase diagram that can be used to determine how certain types of fluid flow will influence deformation and, ultimately, the physical properties of soft particles when pulled on from different flow directions.
"For example, products like fabric softeners - which are composed of vesicle suspensions - do not work correctly when they clump together," Kumar said. "Using the Stokes trap, we can figure out what types of particle interactions cause the vesicles to aggregate and then design a better-performing material."
The technique is currently limited by the size of particles that the Stokes trap can catch and handle, the researchers said. They are working with particles that generally are larger than 100 nanometers in diameter, but in order for this technology to apply more directly to biological systems, they will need to be able to grab particles that are 10 to 20 nanometers in diameter - or even down to a single protein.
The researchers are currently working to capture smaller particles and to apply the Stokes trap to study membrane proteins.
The newest study has been published in the journal Soft Matter, while the previous two have been published in the journals Physical Review Fluids and Physical Review Applied.
U.S. President Donald Trump on Tuesday downplayed the significance of a possible "Christmas surprise" from Pyongyang, saying he would deal with it successfully.
"We'll find out what the surprise is and we'll deal with it very successfully," Trump told reporters at his resort Mar-a-Lago, Florida when asked about the Democratic People's Republic of Korea (DPRK)'s threat of a possible "Christmas surprise."
"Everybody's got surprises for me ... I handle them as they come along," he said, adding that the DPRK might send him "a beautiful vase" instead of a missile test.
DPRK's Vice Foreign Minister Ri Thae Song warned in early December that Washington would soon need to decide what kind of "Christmas gift" it will receive from Pyongyang.
Pyongyang had set its deadline for the denuclearization negotiations at the end of this year, and it also carried out two "important tests" at its Sohae Satellite Launching Ground on Dec. 7 and 13.
The denuclearization negotiation between Washington and Pyongyang has lost momentum since the impasse of the Hanoi Summit in late February and the unproductive working-level talks in Stockholm in October.
President Vladimir Putin said Tuesday that Russia is the only country in the world that has hypersonic weapons.
Speaking at a meeting with top military brass, Putin said that for the first time in history Russia has an edge in designing a new class of weapons unlike in the past when it was catching up with the United States.
He said that the first unit equipped with the Avangard hypersonic glide vehicle is set to go on duty this month, while that the air-launched Kinzhal hypersonic missiles already have entered service.
Putin first mentioned the Avangard and the Kinzhal among other prospective weapons systems in his state-of-the-nation address in March 2018.
Putin said then that the Avangard has an intercontinental range and can fly in the atmosphere at a speed 20 times the speed of sound. He noted that the weapon's ability to change both its course and its altitude en route to a target makes it immune to interception by the the enemy.
Speaking Tuesday, he described the Avangard as a "weapon of the future, capable of penetrating both existing and prospective missile defense systems."
The Kinzhal, which is carried by MiG-31 fighter jets, entered service with the Russian air force last year. Putin has said that the missile flies 10 times faster than the speed of sound, has a range of more than 2,000 kilometers (1,250 miles) and can carry a nuclear or a conventional warhead. The military said it's capable of hitting both land targets and navy ships.
The United States and other countries also have worked on designing hypersonic weapons, but they haven't entered service yet.
At least 31 Boko Haram militants were killed in a gunfight when the troops laid an ambush for them in Nigeria's northeastern state of Yobe, a spokesman for the army said on Monday.
Njoka Irabor, a spokesman for the army in the northeast region, said a commander of the Boko Haram group identified as Mukhtar was among those killed in the encounter late Sunday in Damaturu, the capital of Yobe.
Mukhtar was known to have coordinated most of the ambushes against the Nigerian troops along the fringes of Lake Chad, Irabor said.
According to the spokesman, the terror group had attempted to invade the city of Damaturu to wreak havoc on the residents but the troops thwarted the attack.
The gunfight, which prevented the Boko Haram militants from gaining entry into the city, lasted at least three hours, the spokesman said.
The northeast region in Nigeria has been destabilized for over a decade by Boko Haram, which most notoriously kidnapped hundreds of schoolgirls in 2014.
Boko Haram is known for its agenda to maintain a virtual caliphate in the most populous African country.
Botswana said on Monday that it is fighting rhino poaching harder in the Okavango Delta in the northern part of the country.
The Ministry of Environment, Natural Resources Conservation and Tourism said in a statement that the government has stepped up its efforts to address rhino poaching and recovered some horns and hunting weapons in related operations.
Statistics show that nine rhinos were killed between April 1 and Oct. 4 this year.
"From October 2019 to date, 13 more rhinos have been poached," said the statement.
"During engagement with the poachers, seven casualties occurred amongst poachers who were resisting arrest. The government will continue to do all it can to ensure the protection of this iconic species," Alice Mmolawa, spokesperson of the ministry, said in the statement.
She appealed to stakeholders including communities and the private sector to support rhino protection efforts.
"We further call upon members of the community to be vigilant and report any suspicious activities in and around the Okavango Delta to the nearest security agents," Mmolawa said.