It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
Thursday, January 04, 2024
Online racial discrimination, suicidal ideation, and traumatic stress in a national sample of Black adolescents
About The Study: This study that included 525 Black adolescents found an association between individual online racial discrimination and posttraumatic stress disorder symptoms and between posttraumatic stress disorder symptoms and suicidal ideation. These risk factors are important to consider in continuing studies of the cause of suicidal ideation for Black adolescents in the U.S.
Authors: Brendesha M. Tynes, Ph.D., of the University of Southern California, Los Angeles, is the corresponding author.
Editor’s Note: Please see the article for additional information, including other authors, author contributions and affiliations, conflict of interest and financial disclosures, and funding and support.
RESEARCHERS AT THE GEORGIA INSTITUTE OF TECHNOLOGY HAVE CREATED THE WORLD’S FIRST FUNCTIONAL SEMICONDUCTOR MADE FROM GRAPHENE, A SINGLE SHEET OF CARBON ATOMS HELD TOGETHER BY THE STRONGEST BONDS KNOWN. THE BREAKTHROUGH THROWS OPEN THE DOOR TO A NEW WAY OF DOING ELECTRONICS.
Researchers at the Georgia Institute of Technology have created the world’s first functional semiconductor made from graphene, a single sheet of carbon atoms held together by the strongest bonds known. Semiconductors, which are materials that conduct electricity under specific conditions, are foundational components of electronic devices. The team’s breakthrough throws open the door to a new way of doing electronics.
Their discovery comes at a time when silicon, the material from which nearly all modern electronics are made, is reaching its limit in the face of increasingly faster computing and smaller electronic devices. Walter de Heer, Regents’ Professor of physics at Georgia Tech, led a team of researchers based in Atlanta, Georgia, and Tianjin, China, to produce a graphene semiconductor that is compatible with conventional microelectronics processing methods — a necessity for any viable alternative to silicon.
In this latest research, published in Nature, de Heer and his team overcame the paramount hurdle that has been plaguing graphene research for decades, and the reason why many thought graphene electronics would never work. Known as the “band gap,” it is a crucial electronic property that allows semiconductors to switch on and off. Graphene didn’t have a band gap — until now.
“We now have an extremely robust graphene semiconductor with 10 times the mobility of silicon, and which also has unique properties not available in silicon,” de Heer said. “But the story of our work for the past 10 years has been, ‘Can we get this material to be good enough to work?’”
A New Type of Semiconductor
De Heer started to explore carbon-based materials as potential semiconductors early in his career, and then made the switch to exploring two-dimensional graphene in 2001. He knew then that graphene had potential for electronics.
“We were motivated by the hope of introducing three special properties of graphene into electronics,” he said. “It’s an extremely robust material, one that can handle very large currents, and can do so without heating up and falling apart.”
De Heer achieved a breakthrough when he and his team figured out how to grow graphene on silicon carbide wafers using special furnaces. They produced epitaxial graphene, which is a single layer that grows on a crystal face of the silicon carbide. The team found that when it was made properly, the epitaxial graphene chemically bonded to the silicon carbide and started to show semiconducting properties.
Over the next decade, they persisted in perfecting the material at Georgia Tech and later in collaboration with colleagues at the Tianjin International Center for Nanoparticles and Nanosystems at Tianjin University in China. De Heer founded the center in 2014 with Lei Ma, the center’s director and a co-author of the paper.
How They Did It
In its natural form, graphene is neither a semiconductor nor a metal, but a semimetal. A band gap is a material that can be turned on and off when an electric field is applied to it, which is how all transistors and silicon electronics work. The major question in graphene electronics research was how to switch it on and off so it can work like silicon.
But to make a functional transistor, a semiconducting material must be greatly manipulated, which can damage its properties. To prove that their platform could function as a viable semiconductor, the team needed to measure its electronic properties without damaging it.
They put atoms on the graphene that “donate” electrons to the system — a technique called doping, used to see whether the material was a good conductor. It worked without damaging the material or its properties.
The team’s measurements showed that their graphene semiconductor has 10 times greater mobility than silicon. In other words, the electrons move with very low resistance, which, in electronics, translates to faster computing. “It’s like driving on a gravel road versus driving on a freeway,” de Heer said. “It’s more efficient, it doesn’t heat up as much, and it allows for higher speeds so that the electrons can move faster.”
The team’s product is currently the only two-dimensional semiconductor that has all the necessary properties to be used in nanoelectronics, and its electrical properties are far superior to any other 2D semiconductors currently in development.
“A long-standing problem in graphene electronics is that graphene didn’t have the right band gap and couldn’t switch on and off at the correct ratio,” said Ma. “Over the years, many have tried to address this with a variety of methods. Our technology achieves the band gap, and is a crucial step in realizing graphene-based electronics.”
Moving Forward
Epitaxial graphene could cause a paradigm shift in the field of electronics and allow for completely new technologies that take advantage of its unique properties. The material allows the quantum mechanical wave properties of electrons to be utilized, which is a requirement for quantum computing.
“Our motivation for doing graphene electronics has been there for a long time, and the rest was just making it happen,” de Heer said. “We had to learn how to treat the material, how to make it better and better, and finally how to measure the properties. That took a very, very long time.”
According to de Heer, it is not unusual to see yet another generation of electronics on its way. Before silicon, there were vacuum tubes, and before that, there were wires and telegraphs. Silicon is one of many steps in the history of electronics, and the next step could be graphene.
“To me, this is like a Wright brothers moment,” de Heer said. “They built a plane that could fly 300 feet through the air. But the skeptics asked why the world would need flight when it already had fast trains and boats. But they persisted, and it was the beginning of a technology that can take people across oceans.”
Citation: Zhao, J. et al. Ultrahigh-mobility semiconducting epitaxial graphene on silicon carbide. Nature (2024).
The Georgia Institute of Technology, or Georgia Tech, is one of the top public research universities in the U.S., developing leaders who advance technology and improve the human condition. The Institute offers business, computing, design, engineering, liberal arts, and sciences degrees. Its more than 45,000 undergraduate and graduate students, representing 50 states and more than 148 countries, study at the main campus in Atlanta, at campuses in France and China, and through distance and online learning. As a leading technological university, Georgia Tech is an engine of economic development for Georgia, the Southeast, and the nation, conducting more than $1 billion in research annually for government, industry, and society.
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A single crystal silicon carbide wafer that has been cut into square chips.
The team's graphene device grown on a silicon carbide substrate chip.
De Heer's patented induction furnace used to produce graphene on silicon carbide.
Molecular models of graphene and silicon carbide.
A vial of graphene grown in a furnace at de Heer's lab at Georgia Tech.
Walter de Heer, professor of physics at the Georgia Institute of Technology, holds a silicon carbide wafer.
RESEARCHERS AT WASHINGTON UNIVERSITY SCHOOL OF MEDICINE IN ST. LOUIS HAVE DETERMINED HOW EASTERN EQUINE ENCEPHALITIS VIRUS ATTACHES TO A RECEPTOR IT USES TO ENTER AND INFECT CELLS. THE WHOLE VIRUS IS SHOWN ON THE LEFT AND A MAGNIFIED VIEW OF THE VIRAL STRUCTURAL PROTEINS ON THE RIGHT. THE FINDINGS LAID THE GROUNDWORK FOR A RECEPTOR DECOY MOLECULE THAT PROTECTS MICE FROM ENCEPHALITIS CAUSED BY THE VIRUS.
An atomic-level investigation of how Eastern equine encephalitis virus binds to a key receptor and gets inside of cells also has enabled the discovery of a decoy molecule that protects against the potentially deadly brain infection, in mice.
The study, from researchers at Washington University School of Medicine in St. Louis, is published Jan. 3 in the journal Cell. By advancing understanding of the complex molecular interactions between viral proteins and their receptors on animal cells, the findings lay a foundation for treatments and vaccines for viral infections.
“Understanding how viruses engage with the cells they infect is a critical part of preventing and treating viral disease,” said co-senior author Michael S. Diamond, MD, PhD, the Herbert S. Gasser Professor at Washington University. “Once you understand that, you have the foundation for developing vaccines and drugs to block it. In this study, it took us a long time to sort out the complexity associated with the particular receptor-virus interaction, but once we acquired this knowledge, we were able to design a decoy molecule that turned out to be very effective at neutralizing the virus and protecting mice from disease.”
Though infections of Eastern equine encephalitis virus in people are rare — with only a few cases reported worldwide each year — about one-third of those with the infection die, and many survivors suffer lasting neurological problems. Further, scientists predict that as the planet warms and climate change lengthens mosquito populations’ seasons and geographical reach, risk of infection will grow. At present, there are no approved vaccines against the virus or specific medications to treat it.
As a first step to finding ways to treat or prevent the deadly virus, Diamond and co-senior author Daved H. Fremont, PhD, a professor of pathology & immunology, set about investigating how the virus attaches to one of its key receptors — a molecule called VLDLR, or very low density lipoprotein receptor. The molecule is found on the surface of cells in the brain and other parts of the body. Co-first author Lucas Adams, an MD/PhD student in the Fremont and Diamond laboratories, used cryo-electron microscopy to reconstruct the virus binding to the receptor in atomic-level detail.
The results turned out to be unexpectedly complex. The molecule is composed of eight repeated segments, called domains, strung together like beads on a chain. Usually, a viral protein and its receptor fit together in one very specific way. In this case, however, two or three different spots on the viral surface proteins were capable of attaching to any of five of the molecule’s eight domains.
“What’s really striking is that we find multiple binding sites, but the chemistry of each of the binding sites is very similar and also similar to the chemistry of binding sites for other viruses that interact with related receptors,” said Fremont, who is also a professor of biochemistry & molecular biophysics and of molecular microbiology. “The chemistry just works out well for the way viruses want to attach to cell membranes.”
The domains that make up this molecule also are found in several related cell-surface proteins. Similar domains are found in proteins from across the animal kingdom.
“Since they’re using a molecule that naturally has repetitive domains, some of the alphaviruses have evolved to use the same strategy of attachment with multiple different domains in the same receptor,” said Diamond, who is also a professor of medicine, of molecular microbiology, and of pathology & immunology. Alphaviruses include Eastern equine encephalitis virus and several other viruses that cause brain or joint disease. “There are sequence differences in the VLDLR receptor over evolution in different species, but since the virus has this flexibility in binding, it is able to infect a wide variety of species including mosquitoes, birds, rodents and humans.”
To block attachment, the researchers created a panel of decoy receptors by combining subsets of the eight domains. The idea was that the virus mistakenly would bind to the decoy instead of the receptor on cells, and the decoy with the virus attached could then be cleared away by immune cells.
Co-first author Saravanan Raju, MD, PhD, a postdoctoral researcher in the Diamond lab, evaluated the panel of decoys. First, he tested them on cells in dishes. Many neutralized the virus. Then, he turned to mice. Raju pretreated mice with a decoy or saline solution, as a control, six hours before injecting the virus under their skin, a mode of infection that mimics natural infection via mosquito bite. Three decoys were tested: one known to be unable to neutralize the virus; one made from the full-length molecule; and one made from just the first two domains.
All of the mice that received saline solution, the non-neutralizing decoy or the full-length decoy died within eight days of infection. All of the mice that received the decoy made from the first two domains survived without signs of illness.
Certain aspects of its biology give Eastern equine encephalitis virus the potential to be weaponized, making it particularly important to find a way to protect against it. In a subsequent experiment in which the mice were infected by inhalation — as would happen if the virus were aerosolized and used as a bioweapon — the decoy made from the first two domains was still effective, reducing the mice’s chance of death by 70%.
“Through a combination of the structural work and the domain deletion work, we were able to figure out which domains are the most critical and create a quite effective decoy receptor that can neutralize viral infection,” Fremont said. “This study broadens what we know about virus-receptor interactions and could lead to new approaches to preventing viral infections.”
Structural and functional basis of VLDLR usage by Eastern equine encephalitis virus
ARTICLE PUBLICATION DATE
3-Jan-2024
COI STATEMENT
Diamond is a consultant or adviser for Inbios, Ocugen, Vir Biotechnology, Topspin Therapeutics, Moderna, Merck, and Immunome. The Diamond laboratory has received funding support from Emergent BioSolutions, Moderna, and Vir Biotechnology. Fremont is a founder of Courier Therapeutics and has received funding support from Emergent BioSolutions and Mallinckrodt Pharmaceuticals.
Computational method discovers hundreds of new ceramics for extreme environments
A new computational method unveils hundreds of new ceramic materials with a wide range of potentially industry-disrupting properties like electronics that could function in a lava bath
AN ARTISTIC REPRESENTATION OF THE MOLECULAR STRUCTURE OF THE NEWLY DISCOVERED CERAMIC MATERIALS THAT COULD POTENTIALLY DISRUPT SEVERAL INDUSTRIES THANKS TO THEIR ABILITY TO CREATE FUNCTIONAL ELECTRONICS AT THOUSANDS OF DEGREES.
DURHAM, N.C. – If you have a deep-seated, nagging worry over dropping your phone in molten lava, you’re in luck.
A research team led by materials scientists at Duke University has developed a method for rapidly discovering a new class of materials with heat and electronic tolerances so rugged that they that could enable devices to function at lava-like temperatures above several thousands of degrees Fahrenheit.
Harder than steel and stable in chemically corrosive environments, these materials could also form the basis of new wear- and corrosion-resistant coatings, thermoelectrics, batteries, catalysts and radiation-resistant devices.
The recipes for these materials — ceramics made using transition metals carbonitrides or borides — were discovered through a new computational method called Disordered Enthalpy-Entropy Descriptor (DEED). In its first demonstration, the program predicted the synthesizability of 900 new formulations of high-performance materials, 17 of which were then tested and successfully produced in laboratories.
The results appear online January 3 in the journal Nature and include contributions from collaborators at Penn State University, Missouri University of Science and Technology, North Carolina State University, and State University of New York at Buffalo.
“The capability of rapidly discovering synthesizable compositions will allow researchers to focus on optimizing their industry-disrupting properties,” said Stefano Curtarolo, the Edmund T. Pratt Jr. School Distinguished Professor of Mechanical Engineering and Materials Science at Duke.
The Curtarolo group maintains the Duke Automatic-FLOW for Materials Database (AFLOW)—an enormous reservoir of material properties data connected to many online tools for materials optimization. This wealth of information allows algorithms to accurately predict the properties of unexplored mixtures without having to attempt to simulate the complexities of atomic dynamics or make them in the laboratory.
For the past several years, the Curtarolo group has been working to develop predictive powers for “high-entropy” materials that derive enhanced stability from a chaotic mixture of atoms rather than relying solely on the orderly atomic structure of conventional materials. In 2018, they discovered high-entropy carbides, which were a simpler, special-case scenario.
“The high-entropy carbides all had a relatively uniform amount of enthalpy, so we could ignore part of the equation,” Curtarolo said. “But to predict new ceramic recipes with other transition metals, we had to address the enthalpy.”
To better understand the concepts of entropy and enthalpy in this application, think of a 10-year-old trying to construct a doghouse out of a giant pile of Legos. Even with limited types of building blocks, there would be many possible design outcomes.
In simple terms, enthalpy is a measure of how sturdy each design is, and entropy a measure of the number of possible designs that all have similar strength. The first promotes ordered configurations, like those that might be found in instruction booklets. The latter captures the unavoidable chaos that would occur as the child puts more time and energy into the increasingly confusing construction effort. Both are a measure of the amount of energy and heat that end up being absorbed into the final product.
“To rapidly quantify both enthalpy and entropy, we had to calculate the energy contained within the hundreds of thousands of various combinations of ingredients that we could potentially create instead of the ceramics we’re looking for,” Curtarolo said. “It was a mammoth undertaking.”
Besides predicting new recipes for stable disordered ceramics, DEED also helps direct their further analysis to discover their inherent properties. To find the optimal ceramics for various applications, researchers will need to refine these calculations and physically test them in laboratories.
DEED is specifically tailored to a production method called hot-pressed sintering. This involves taking powdered forms of the constituent compounds and heating them in a vacuum to as high as 4000 degrees Fahrenheit while applying pressure for times that can be as long as a few hours. Between all the preparation, reaction and cooling times, the entire process takes more than eight hours.
“The final step in synthesis, called spark plasma sintering, is an emerging method in materials science that is common in research labs,” said William Fahrenholtz, the Curators’ Distinguished Professor of Ceramic Engineering at Missouri S&T.
The finished ceramics have a metallic appearance and look dark grey or black. They feel like metal alloys such as stainless steel and have a similar density, but they are much darker in appearance. And even though they appear metallic, they are hard and brittle like conventional ceramics.
Moving forward, the group expects other researchers to begin using DEED to synthesize and test the properties of new ceramic materials for various applications. Given the incredible array of potential properties and uses, they believe it’s only a matter of time before some of them enter commercial production.
“Spark plasma sintering or field assisted sintering technology (FAST) is not a common technique in industry yet,” added Doug Wolfe, professor of materials science and engineering and associate vice president for research at Penn State. “However, current ceramic manufacturers could pivot to making these materials by making small adjustments to existing processes and facilities.”
This research was primarily supported by a five-year, $7.5 million grant through the US Department of Defense’s Multidisciplinary University Research Initiative (MURI) competition led by Curtarolo (N00014-21-1-2515, N00014-23-1-2615) and the Department of Defense High Performance Computing Modernization Program (HPC-Frontier).
CITATION: “Disordered Enthalpy-Entropy Descriptor for High-Entropy Ceramics Discovery,” Simon Divilov, Hagen Eckert, David Hicks, Corey Oses, Cormac Toher, Rico Friedrich, Marco Esters, Michael J. Mehl, Adam C. Zettel, Yoav Lederer, Eva Zurek, Jon-Paul Maria, Donald W. Brenner, Xiomara Campilongo, Suzana Filipović, William G. Fahrenholtz, Caillin J. Ryan, Christopher M. DeSalle, Ryan J. Crealese, Douglas E. Wolfe, Arrigo Calzolari and Stefano Curtarolo. Nature, Jan. 3, 2024`. DOI: 10.1038/s41586-023-06786-y
INDIANAPOLIS—A beta blocker typically used to treat heart problems, hemangioma, migraines and anxiety could be a new therapeutic for patients with sickle cell disease. Researchers led by Ankit A. Desai, MD, associate professor of medicine at the Krannert Cardiovascular Research Center (KCVRC) at Indiana University School of Medicine, have been awarded a $3 million grant by the U.S. Department of Defense to evaluate the efficacy of this drug.
Patients with sickle cell disease, a red blood cell disorder that can cause harm to multiple organs when red blood vessels are blocked or when the cells break down, are at risk of major complications when they also develop heart damage. The median age of death is 43 years old.
“Cardiomyopathy or heart damage can predispose patients to a fatal rhythm disturbance called ventricular tachycardia,” Desai said. “We believe that inflammation plays a key role in both, creating this injurious heart and exacerbating it. We are deeply interested in translating this potential therapeutic to patients, developing a clinical trial and trying to understand the impact R-propranolol, given that propranolol appears to be well tolerated in patients otherwise.”
Propranolol is a mixture of two chemical formulations – R-prop and S-Propranolol, which are similar in composition. The only difference is that R-prop does not demonstrate as much beta blocker activity. The team also plans to evaluate potential for toxicity before introducing R-prop in a clinical trial.
“Evaluating a therapeutic that has already been consumed by millions for other diseases could help accelerate the potential use in patients with sickle cell more quickly,” said Desai, principal investigator of the study, a cardiologist at IU Health and leader of KCVRC’s Cardiopulmonary Research Program. “This grant will allow us to study heart injury as well as rhythm disturbance impact in preclinical models of sickle cell disease. The study funds a disease that is underrecognized and underrepresented and supports a broader goal at closing health care gaps.”
Desai will collaborate with Bum-Rak Choi, PhD, associate professor of medicine at Rhode Island Hospital and Brown University. He will work closely with Choi on data related to the development of fatal arrhythmias in sickle cell disease.
“While new therapies are being explored, cleverly repurposed drugs that have already had human exposure with strong safety profile, such as R-propranolol, stand to make major headway in solving a long-standing health issue affecting the heart and cardiovascular system in the United States and abroad,” said Rohan Dharmakumar, PhD, executive director of the KCVRC.
About IU School of Medicine
IU School of Medicine is the largest medical school in the U.S. and is annually ranked among the top medical schools in the nation by U.S. News & World Report. The school offers high-quality medical education, access to leading medical research and rich campus life in nine Indiana cities, including rural and urban locations consistently recognized for livability
Researchers improve seed nitrogen content by reducing plant chlorophyll levels
CARL R. WOESE INSTITUTE FOR GENOMIC BIOLOGY, UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN
IMAGE:
YOUNG CHO USED AN ETHANOL SPRAY TO REDUCE THE CHLOROPHYLL LEVELS IN LEAVES. THE SPRAY INDUCED SMALL RNA THAT INTERFERED WITH CHLOROPHYLL SYNTHESIS RESULTING IN PALE YELLOW PLANTS, AND THE UNTREATED PLANTS REMAINED COMPLETELY GREEN.
Chlorophyll plays a pivotal role in photosynthesis, which is why plants have evolved to have high chlorophyll levels in their leaves. However, making this pigment is expensive because plants invest a significant portion of the available nitrogen in both chlorophyll and the special proteins that bind it. As a result, nitrogen is unavailable for other processes. In a new study, researchers reduced the chlorophyll levels in leaves to see if the plant would invest the nitrogen saved into other process that might improve nutritional quality.
Over the past few decades, researchers have been trying to increase crop yield to meet the global food demand. One of their biggest challenges has been to improve the photosynthetic efficiency of agricultural crops.
When light hits a leaf, one of three things can happen: the leaf can absorb the light for photosynthesis, the leaf can reflect it back into the atmosphere, or the light can pass through the leaf. Unfortunately, even though a fully green leaf absorbs over 90% of the light that hits it, the leaf doesn’t use it all for photosynthesis.
“We grow our crop plants at very high densities. As a result, although the leaves at the top of the canopy have more light, they cannot use it all and the layer below is light starved,” said Don Ort (GEGC leader/CABBI/BSD), a professor of integrative biology. “Our rationale was to reduce the amount of chlorophyll at the top of the canopy so more light can penetrate and be used more efficiently lower in the canopy.”
In the current study, the researchers engineered tobacco plants to have lower chlorophyll levels as the crop canopy grows more dense.
“Previous models have shown that if you have lower chlorophyll levels before you have a dense canopy, it is detrimental to plant growth,” Ort said. “We wanted to take plants that have full canopies and ensure that the new leaves that are added on top have lower chlorophyll levels.”
To do so, the researchers used small RNAs that interfere with key steps in chlorophyll synthesis. The production of these small RNAs were put under the control of an inducible promoter—a piece of DNA that responds to a specific signal and directs the cell to produce RNA.
In the study, the researchers used an ethanol-inducible promoter. When they sprayed the leaves with ethanol, the resulting small RNAs interfered with the synthesis of chlorophyll, creating a canopy that had a lighter shade of green.
“We found that even when chlorophyll synthesis decreased 70%, there was no inhibition of growth,” said Young Cho, a postdoctoral researcher in the Ort lab and the study’s lead author. “Although we had theoretically predicted this result, observing these pale green or yellow plants growing normally was astonishing, considering that such discoloration typically indicates plant illness.”
The researchers had also hypothesized that decreasing the amount of chlorophyll would influence other aspects of plant growth because it would free up the nitrogen that was being invested into making the pigment and associated proteins. They were proven right when they saw that the seed nitrogen concentration was 17% higher in the plants in which the ethanol-inducible promoter controlling the interfering small RNAs were activated.
“We had also expected an increase in yield because as you get more light into the canopy, you would expect it to be used more efficiently,” Ort said. “However, we didn’t detect an increase, which probably means that the plants did not invest enough of the extra nitrogen to improve the photosynthetic capacity in the lower parts of the canopy. This result gives us another engineering target.”
In their future work, the researchers will test whether they can get similar results with light-inducible promoters, which farmers will find easier to use. “Ethanol-inducible promoters are very convenient and important research tools. However, farmers will not want to spray an entire field with ethanol, so we need to look at other promoters that respond to the intensity or the color of light,” Ort said.
The study “Reducing chlorophyll levels in seed-filling stages results in higher seed nitrogen without impacting canopy carbon assimilation,” was published in Plant, Cell & Environment and can be found at https://doi.org/10.1111/pce.14737.
This work is supported by the research project Realizing Increased Photosynthetic Efficiency (RIPE) which is funded by the Bill & Melinda Gates Foundation, Foundation for Food and Agriculture Research, and U.K. Foreign, Commonwealth & Development Office.
