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Clemson researchers decode thermal conductivity with light

Clemson researchers decode thermal conductivity with light

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Clemson scientists work with international team

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Credit: Image Credit: College of Science

CLEMSON, South Carolina – Groundbreaking science is often the result of true collaboration, with researchers in a variety of fields, viewpoints and experiences coming together in a unique way. One such effort by Clemson University researchers has led to a discovery that could change the way the science of thermoelectrics moves forward.

Graduate research assistant Prakash Parajuli; research assistant professor Sriparna Bhattacharya; and Clemson Nanomaterials Institute (CNI) Founding Director Apparao Rao (all members of CNI in the College of Science’s Department of Physics and Astronomy) worked with an international team of scientists to examine a highly efficient thermoelectric material in a new way – by using light.

Their research has been published in the journal Advanced Science and is titled “High zT and its origin in Sb-doped GeTe single crystals.”

“Thermoelectric materials convert heat energy into useful electric energy; therefore, there is a lot of interest in materials that can convert it most efficiently,” Parajuli said

Bhattacharya explained that the key to measuring progress in the field is the figure of merit, noted as zT, which is highly dependent on the property of thermoelectric materials. “Many thermoelectric materials exhibit a zT of 1-1.5, which also depends on the temperature of the thermoelectric material. Only recently have materials with a zT of 2 or higher have been reported.”

“This begs the question, how many more such materials can we find, and what is the fundamental science that is new here through which a zT greater than 2 can be achieved?” Rao added. “Basic research is the seed from which applied research grows, and to stay at the forefront in thermoelectrics we teamed up with professor Yang Yuan Chen’s team at the Academia Sinica, Taiwan.”

Chen and Rao’s teams focused on Germanium Telluride (GeTe), a single crystal material.

“GeTe is of interest, but plain GeTe without any doping does not show exciting properties,” Bhattacharya said. “But once we add a little bit of antimony to it, it does show good electronic properties, as well as very low thermal conductivity.”

While others have reported GeTe-based materials with high zT, these were polycrystalline materials. Polycrystals have boundaries among the many small crystals of which they are formed. While such boundaries favorably impede heat transfer, they mask the origin of fundamental processes that lead to high zT.

“Here, we had pure and doped GeTe single crystals whose thermoelectric properties have not been reported,” Bhattacharya said. “Therefore, we were able to evaluate the intrinsic properties of these materials that would otherwise be difficult to decipher in the presence of competing processes. This may be the first GeTe crystal with antimony doping that showed these unique properties – mainly the ultra-low thermal conductivity.”

This low thermal conductivity came as a surprise, since the material’s simple crystalline structure should allow for heat to flow easily throughout the crystal.

“Electrons carry the heat and electricity, so if you block the electrons, you have no electricity,” Parajuli said. “Hence, the key is to block the flow of heat by the quantized lattice vibrations known as phonons, while allowing electrons to flow.”

Doping GeTe with the right amount of antimony can maximize electron flow and minimize heat flow. This study found that the presence of 8 antimony atoms for every 100 GeTe gives rise to a new set of phonons, which effectively reduce heat flow that was confirmed both experimentally and theoretically.

The team, along with collaborators who grew the crystals, performed electronic and thermal transport measurements in addition to density functional theory calculations to find this mechanism in two ways: first, through modeling, using the thermal conductivity data; second, through Raman spectroscopy, which probes the phonons within a material.

“This is a totally new angle for thermoelectric research,” Rao said. “We are sort of pioneers in that way – decoding thermal conductivity in thermoelectrics with light. What we found using light agreed well with what was found through thermal transport measurements. Future research in thermoelectrics should use light – it’s a very powerful nondestructive method to elucidate heat transport in thermoelectrics. You shine light on the sample, and collect information. You aren’t destroying the sample.”

Rao said that the collaborators’ wide range of expertise was key to their success. The group included Fengjiao Liu, a former Ph.D. student at CNI; Rahul Rao, Research Physical Scientist at the ?Air Force Research Laboratory, Wright-Patterson Air Force Base; and Oliver Rancu, a high school student at the South Carolina Governor’s School for Science and Mathematics who worked with the team through Clemson’s SPRI (Summer Program for Research Interns) program. Because of the pandemic, the team worked with Rancu via Zoom, guiding him with some of Parajuli’s calculations using an alternate Matlab code.

“I am so very grateful for the opportunity to work with the CNI team members this summer,” said Rancu, who hails from Anderson, South Carolina. “I have learned so many things about both physics and the research experience in general. It truly was priceless, and this research publication is just another addition to an already fantastic experience.”

“I was very impressed by Oliver,” Parajuli added. “He caught on quickly with the necessary framework for the theory.”

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Additional contributors to the paper include Ranganayakulu Vankayala with the Institute of Physics, Academia Sinica, Taiwan, National Tsing Hua University and Taiwan International Graduate Program; Tian-Wey Lan, Shih Hsun Yu, Tsu-Lien Hung, Cheng-Lung Chen and Min-Nan Ou with the Institute of Physics, Academia Sinica, Taiwan; Chih-Hao Lee with National Tsing Hua University; Shin-Ichiro Yano with the National Synchrotron Radiation Research Center, Taiwan; and Cheng-Rong Hsing, Duc-Long Nguyen and Kuei-Hsien Chen with the Institute of Atomic and Molecular Sciences, Taiwan.

Media Contact
Jim Melvin
jsmelvi@clemson.edu

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http://newsstand.clemson.edu/mediarelations/clemson-researchers-decode-thermal-conductivity-in-thermoelectrics-using-light/

Related Journal Article

http://dx.doi.org/10.1002/advs.202002494

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Are Voters Recoiling Against Disorder?

Are Voters Recoiling Against Disorder?

Authored by Michael Barone via The Epoch Times (emphasis ours),

The headlines coming out of the Super…

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Are Voters Recoiling Against Disorder?

Authored by Michael Barone via The Epoch Times (emphasis ours),

The headlines coming out of the Super Tuesday primaries have got it right. Barring cataclysmic changes, Donald Trump and Joe Biden will be the Republican and Democratic nominees for president in 2024.

(Left) President Joe Biden delivers remarks on canceling student debt at Culver City Julian Dixon Library in Culver City, Calif., on Feb. 21, 2024. (Right) Republican presidential candidate and former U.S. President Donald Trump stands on stage during a campaign event at Big League Dreams Las Vegas in Las Vegas, Nev., on Jan. 27, 2024. (Mario Tama/Getty Images; David Becker/Getty Images)

With Nikki Haley’s withdrawal, there will be no more significantly contested primaries or caucuses—the earliest both parties’ races have been over since something like the current primary-dominated system was put in place in 1972.

The primary results have spotlighted some of both nominees’ weaknesses.

Donald Trump lost high-income, high-educated constituencies, including the entire metro area—aka the Swamp. Many but by no means all Haley votes there were cast by Biden Democrats. Mr. Trump can’t afford to lose too many of the others in target states like Pennsylvania and Michigan.

Majorities and large minorities of voters in overwhelmingly Latino counties in Texas’s Rio Grande Valley and some in Houston voted against Joe Biden, and even more against Senate nominee Rep. Colin Allred (D-Texas).

Returns from Hispanic precincts in New Hampshire and Massachusetts show the same thing. Mr. Biden can’t afford to lose too many Latino votes in target states like Arizona and Georgia.

When Mr. Trump rode down that escalator in 2015, commentators assumed he’d repel Latinos. Instead, Latino voters nationally, and especially the closest eyewitnesses of Biden’s open-border policy, have been trending heavily Republican.

High-income liberal Democrats may sport lawn signs proclaiming, “In this house, we believe ... no human is illegal.” The logical consequence of that belief is an open border. But modest-income folks in border counties know that flows of illegal immigrants result in disorder, disease, and crime.

There is plenty of impatience with increased disorder in election returns below the presidential level. Consider Los Angeles County, America’s largest county, with nearly 10 million people, more people than 40 of the 50 states. It voted 71 percent for Mr. Biden in 2020.

Current returns show county District Attorney George Gascon winning only 21 percent of the vote in the nonpartisan primary. He’ll apparently face Republican Nathan Hochman, a critic of his liberal policies, in November.

Gascon, elected after the May 2020 death of counterfeit-passing suspect George Floyd in Minneapolis, is one of many county prosecutors supported by billionaire George Soros. His policies include not charging juveniles as adults, not seeking higher penalties for gang membership or use of firearms, and bringing fewer misdemeanor cases.

The predictable result has been increased car thefts, burglaries, and personal robberies. Some 120 assistant district attorneys have left the office, and there’s a backlog of 10,000 unprosecuted cases.

More than a dozen other Soros-backed and similarly liberal prosecutors have faced strong opposition or have left office.

St. Louis prosecutor Kim Gardner resigned last May amid lawsuits seeking her removal, Milwaukee’s John Chisholm retired in January, and Baltimore’s Marilyn Mosby was defeated in July 2022 and convicted of perjury in September 2023. Last November, Loudoun County, Virginia, voters (62 percent Biden) ousted liberal Buta Biberaj, who declined to prosecute a transgender student for assault, and in June 2022 voters in San Francisco (85 percent Biden) recalled famed radical Chesa Boudin.

Similarly, this Tuesday, voters in San Francisco passed ballot measures strengthening police powers and requiring treatment of drug-addicted welfare recipients.

In retrospect, it appears the Floyd video, appearing after three months of COVID-19 confinement, sparked a frenzied, even crazed reaction, especially among the highly educated and articulate. One fatal incident was seen as proof that America’s “systemic racism” was worse than ever and that police forces should be defunded and perhaps abolished.

2020 was “the year America went crazy,” I wrote in January 2021, a year in which police funding was actually cut by Democrats in New York, Los Angeles, San Francisco, Seattle, and Denver. A year in which young New York Times (NYT) staffers claimed they were endangered by the publication of Sen. Tom Cotton’s (R-Ark.) opinion article advocating calling in military forces if necessary to stop rioting, as had been done in Detroit in 1967 and Los Angeles in 1992. A craven NYT publisher even fired the editorial page editor for running the article.

Evidence of visible and tangible discontent with increasing violence and its consequences—barren and locked shelves in Manhattan chain drugstores, skyrocketing carjackings in Washington, D.C.—is as unmistakable in polls and election results as it is in daily life in large metropolitan areas. Maybe 2024 will turn out to be the year even liberal America stopped acting crazy.

Chaos and disorder work against incumbents, as they did in 1968 when Democrats saw their party’s popular vote fall from 61 percent to 43 percent.

Views expressed in this article are opinions of the author and do not necessarily reflect the views of The Epoch Times or ZeroHedge.

Tyler Durden Sat, 03/09/2024 - 23:20

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Veterans Affairs Kept COVID-19 Vaccine Mandate In Place Without Evidence

Veterans Affairs Kept COVID-19 Vaccine Mandate In Place Without Evidence

Authored by Zachary Stieber via The Epoch Times (emphasis ours),

The…

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Veterans Affairs Kept COVID-19 Vaccine Mandate In Place Without Evidence

Authored by Zachary Stieber via The Epoch Times (emphasis ours),

The U.S. Department of Veterans Affairs (VA) reviewed no data when deciding in 2023 to keep its COVID-19 vaccine mandate in place.

Doses of a COVID-19 vaccine in Washington in a file image. (Jacquelyn Martin/Pool/AFP via Getty Images)

VA Secretary Denis McDonough said on May 1, 2023, that the end of many other federal mandates “will not impact current policies at the Department of Veterans Affairs.”

He said the mandate was remaining for VA health care personnel “to ensure the safety of veterans and our colleagues.”

Mr. McDonough did not cite any studies or other data. A VA spokesperson declined to provide any data that was reviewed when deciding not to rescind the mandate. The Epoch Times submitted a Freedom of Information Act for “all documents outlining which data was relied upon when establishing the mandate when deciding to keep the mandate in place.”

The agency searched for such data and did not find any.

The VA does not even attempt to justify its policies with science, because it can’t,” Leslie Manookian, president and founder of the Health Freedom Defense Fund, told The Epoch Times.

“The VA just trusts that the process and cost of challenging its unfounded policies is so onerous, most people are dissuaded from even trying,” she added.

The VA’s mandate remains in place to this day.

The VA’s website claims that vaccines “help protect you from getting severe illness” and “offer good protection against most COVID-19 variants,” pointing in part to observational data from the U.S. Centers for Disease Control and Prevention (CDC) that estimate the vaccines provide poor protection against symptomatic infection and transient shielding against hospitalization.

There have also been increasing concerns among outside scientists about confirmed side effects like heart inflammation—the VA hid a safety signal it detected for the inflammation—and possible side effects such as tinnitus, which shift the benefit-risk calculus.

President Joe Biden imposed a slate of COVID-19 vaccine mandates in 2021. The VA was the first federal agency to implement a mandate.

President Biden rescinded the mandates in May 2023, citing a drop in COVID-19 cases and hospitalizations. His administration maintains the choice to require vaccines was the right one and saved lives.

“Our administration’s vaccination requirements helped ensure the safety of workers in critical workforces including those in the healthcare and education sectors, protecting themselves and the populations they serve, and strengthening their ability to provide services without disruptions to operations,” the White House said.

Some experts said requiring vaccination meant many younger people were forced to get a vaccine despite the risks potentially outweighing the benefits, leaving fewer doses for older adults.

By mandating the vaccines to younger people and those with natural immunity from having had COVID, older people in the U.S. and other countries did not have access to them, and many people might have died because of that,” Martin Kulldorff, a professor of medicine on leave from Harvard Medical School, told The Epoch Times previously.

The VA was one of just a handful of agencies to keep its mandate in place following the removal of many federal mandates.

“At this time, the vaccine requirement will remain in effect for VA health care personnel, including VA psychologists, pharmacists, social workers, nursing assistants, physical therapists, respiratory therapists, peer specialists, medical support assistants, engineers, housekeepers, and other clinical, administrative, and infrastructure support employees,” Mr. McDonough wrote to VA employees at the time.

This also includes VA volunteers and contractors. Effectively, this means that any Veterans Health Administration (VHA) employee, volunteer, or contractor who works in VHA facilities, visits VHA facilities, or provides direct care to those we serve will still be subject to the vaccine requirement at this time,” he said. “We continue to monitor and discuss this requirement, and we will provide more information about the vaccination requirements for VA health care employees soon. As always, we will process requests for vaccination exceptions in accordance with applicable laws, regulations, and policies.”

The version of the shots cleared in the fall of 2022, and available through the fall of 2023, did not have any clinical trial data supporting them.

A new version was approved in the fall of 2023 because there were indications that the shots not only offered temporary protection but also that the level of protection was lower than what was observed during earlier stages of the pandemic.

Ms. Manookian, whose group has challenged several of the federal mandates, said that the mandate “illustrates the dangers of the administrative state and how these federal agencies have become a law unto themselves.”

Tyler Durden Sat, 03/09/2024 - 22:10

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Low Iron Levels In Blood Could Trigger Long COVID: Study

Low Iron Levels In Blood Could Trigger Long COVID: Study

Authored by Amie Dahnke via The Epoch Times (emphasis ours),

People with inadequate…

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Low Iron Levels In Blood Could Trigger Long COVID: Study

Authored by Amie Dahnke via The Epoch Times (emphasis ours),

People with inadequate iron levels in their blood due to a COVID-19 infection could be at greater risk of long COVID.

(Shutterstock)

A new study indicates that problems with iron levels in the bloodstream likely trigger chronic inflammation and other conditions associated with the post-COVID phenomenon. The findings, published on March 1 in Nature Immunology, could offer new ways to treat or prevent the condition.

Long COVID Patients Have Low Iron Levels

Researchers at the University of Cambridge pinpointed low iron as a potential link to long-COVID symptoms thanks to a study they initiated shortly after the start of the pandemic. They recruited people who tested positive for the virus to provide blood samples for analysis over a year, which allowed the researchers to look for post-infection changes in the blood. The researchers looked at 214 samples and found that 45 percent of patients reported symptoms of long COVID that lasted between three and 10 months.

In analyzing the blood samples, the research team noticed that people experiencing long COVID had low iron levels, contributing to anemia and low red blood cell production, just two weeks after they were diagnosed with COVID-19. This was true for patients regardless of age, sex, or the initial severity of their infection.

According to one of the study co-authors, the removal of iron from the bloodstream is a natural process and defense mechanism of the body.

But it can jeopardize a person’s recovery.

When the body has an infection, it responds by removing iron from the bloodstream. This protects us from potentially lethal bacteria that capture the iron in the bloodstream and grow rapidly. It’s an evolutionary response that redistributes iron in the body, and the blood plasma becomes an iron desert,” University of Oxford professor Hal Drakesmith said in a press release. “However, if this goes on for a long time, there is less iron for red blood cells, so oxygen is transported less efficiently affecting metabolism and energy production, and for white blood cells, which need iron to work properly. The protective mechanism ends up becoming a problem.”

The research team believes that consistently low iron levels could explain why individuals with long COVID continue to experience fatigue and difficulty exercising. As such, the researchers suggested iron supplementation to help regulate and prevent the often debilitating symptoms associated with long COVID.

It isn’t necessarily the case that individuals don’t have enough iron in their body, it’s just that it’s trapped in the wrong place,” Aimee Hanson, a postdoctoral researcher at the University of Cambridge who worked on the study, said in the press release. “What we need is a way to remobilize the iron and pull it back into the bloodstream, where it becomes more useful to the red blood cells.”

The research team pointed out that iron supplementation isn’t always straightforward. Achieving the right level of iron varies from person to person. Too much iron can cause stomach issues, ranging from constipation, nausea, and abdominal pain to gastritis and gastric lesions.

1 in 5 Still Affected by Long COVID

COVID-19 has affected nearly 40 percent of Americans, with one in five of those still suffering from symptoms of long COVID, according to the U.S. Centers for Disease Control and Prevention (CDC). Long COVID is marked by health issues that continue at least four weeks after an individual was initially diagnosed with COVID-19. Symptoms can last for days, weeks, months, or years and may include fatigue, cough or chest pain, headache, brain fog, depression or anxiety, digestive issues, and joint or muscle pain.

Tyler Durden Sat, 03/09/2024 - 12:50

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