solid-state physics (10)



Researchers have synthesized sheets of gold that are one atom thick. Credit: imaginima/Getty

Topics: Graphene, Materials Science, Nanoengineering, Nanomaterials, Solid-State Physics

It is the world’s thinnest gold leaf: a gossamer sheet of gold just one atom thick. Researchers have synthesized1 the long-sought material, known as goldene, which is expected to capture light in ways that could be useful in applications such as sensing and catalysis.

Goldene is a gilded cousin of graphene, the iconic atom-thin material made of carbon that was discovered in 2004. Since then, scientists have identified hundreds more of these 2D materials. But it has been particularly difficult to produce 2D sheets of metals, because their atoms have always tended to cluster together to make nanoparticles instead.

Researchers have previously reported single-atom-thick layers of tin2 and lead3 stuck to various substances, and they have produced gold sheets sandwiched between other materials. But “we submit that goldene is the first free-standing 2D metal, to the best of our knowledge”, says materials scientist Lars Hultman at Linköping University in Sweden, who is part of the team behind the new research. Crucially, the simple chemical method used to make goldene should be amenable to larger-scale production, the researchers reported in Nature Synthesis on 16 April1.

I’m very excited about it,” says Stephanie Reich, a solid-state physicist and materials scientist at the Free University of Berlin, who was not involved in the work. “People have been thinking for quite some time how to take traditional metals and make them into really well-ordered 2D monolayers.”

In 2022, researchers at New York University Abu Dhabi (NYUAD) said that they had produced goldene, but the Linköping team contends that the prior material probably contained multiple atomic layers, on the basis of the electron microscopy images and other data that were published in ACS Applied Materials and Interfaces4. Reich agrees that the 2022 study failed to prove that the material was singler-layer goldene. The principal authors of the NYUAD study did not respond to Nature’s questions about their work.

Meet ‘goldene’: this gilded cousin of graphene is also one atom thick, Mark Peplow, Nature

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When Falsification Has Lease...

Topics: Applied Physics, Civics, Materials Science, Solid-State Physics, Superconductors

I'm a person who will get Nature on my home email, my previous graduate school email (that's active because it's also on my phone), and my work email. Because it said "physics," I was primed to read it.

What I read made me clasp my hands over my mouth, and periodically stared at the ceiling tiles. My forehead bumped the desk softly, symbolically in disbelief.

Ranga Dias, the physicist at the center of the room-temperature superconductivity scandal, committed data fabrication, falsification and plagiarism, according to a investigation commissioned by his university. Nature’s news team discovered the bombshell investigation report in court documents.

The 10-month investigation, which concluded on 8 February, was carried out by an independent group of scientists recruited by the University of Rochester in New York. They examined 16 allegations against Dias and concluded that it was more likely than not that in each case, the physicist had committed scientific misconduct. The university is now attempting to fire Dias, who is a tenure-track faculty member at Rochester, before his contract expires at the end of the 2024–25 academic year.

Exclusive: official investigation reveals how superconductivity physicist faked blockbuster results

The confidential 124-page report from the University of Rochester, disclosed in a lawsuit, details the extent of Ranga Dias’s scientific misconduct. By Dan Garisto, Nature.

In a nutshell, this is the Scientific Method and how it relates to this investigation:

1. Ask a Question. It can be as simple as "Why is that the way it is?" The question suggests observation, as in, the researcher has read, or seen something in the lab that piqued their curiosity. It is also known as the problem the researcher hopes to solve. The problem must be clear, concise, and testable, i.e., a designed experiment is possible, a survey to gather data can be crafted.

2. Research (n): "the systematic investigation into and study of materials and sources in order to establish facts and reach new conclusions" (Oxford languages). Here, you are "looking for the gaps" in knowledge. People are human, and due to the times and the technology available, something else about a subject may reveal itself through careful examination. The topic area is researched through credible sources, bibliographies, similar published research, textbooks from subject matter experts. Google Scholar counts; grainy YouTube videos don't.

3. The Hypothesis. This encapsulates your research in the form of an idea that can be tested by observation, or experiment. The null hypothesis is a statement or claim that the researcher makes they are trying to disprove, and the alternate hypothesis is a statement or claim the researcher makes they are trying to prove, and with sufficient evidence, disproves the null hypothesis.

4. Design an Experiment. Design of experiments (DOE) follows a set pattern, usually from statistics, or now, using software packages to evaluate input variables, and judging their relationship to output variables. If it sounds like y = f(x), it is.

5. Data Analysis. "The process of systematically applying statistical and/or logical techniques to describe and illustrate, condense and recap, and evaluate data." Source: Responsible Conduct of Research, Northern Illinois University. This succinct definition is the source of my faceplanting regarding this Nature article.

6. Conclusion. R-squared relates to the data gathered, also called the coefficient of determination. Back to the y = f(x) analogy, r-squared is the fit of the data between the independent variables (x) and the output variables (y). An r-squared of 0.90, or 90% and higher, is considered a "good fit" of the data, and the experimenter can make predictions from their results. Did the experimenter disprove the null hypothesis or prove the alternate hypothesis? Were both disproved? (That's called "starting over.")

7. Communication. You craft your results in a journal publication, hopefully one with a high impact factor. If your research helps others in their research ("looking for gaps"), you start seeing yourself appearing in "related research" and "citation" emails from Google Scholar. Your mailbox will fill up, as I hope your self-esteem.

Back to the faceplant:

The 124-page investigation report is a stunning account of Dias’s deceit across the two Nature papers, as well as two other now-retracted papers — one in Chemical Communications3 and one in Physical Review Letters (PRL)4. In the two Nature papers, Dias claimed to have discovered room-temperature superconductivity — zero electrical resistance at ambient temperatures — first in a compound made of carbon, sulfur and hydrogen (CSH)1 and then in a compound eventually found to be made of lutetium and hydrogen (LuH)2.

Capping years of allegations and analyses, the report methodically documents how Dias deliberately misled his co-authors, journal editors and the scientific community. A university spokesperson described the investigation as “a fair and thorough process,” which reached the correct conclusion.

When asked to surrender raw data, Dias gave "massaged" data.

"In several instances, the investigation found, Dias intentionally misled his team members and collaborators about the origins of data. Through interviews, the investigators worked out that Dias had told his partners at UNLV that measurements were taken at Rochester, but had told researchers at Rochester that they were taken at UNLV."

Dias also lied to journals. In the case of the retracted PRL paper4 — which was about the electrical properties of manganese disulfide (MnS2) — the journal conducted its own investigation and concluded that there was apparent fabrication and “a deliberate attempt to obstruct the investigation” by providing reviewers with manipulated data rather than raw data. The investigators commissioned by Rochester confirmed the journal’s findings that Dias had taken electrical resistance data on germanium tetraselenide from his own PhD thesis and passed these data off as coming from MnS2 — a completely different material with different properties (see ‘Odd similarity’). When questioned about this by the investigators, Dias sent them the same manipulated data that was sent to PRL.


Winners and losers

Winners - Scientific Integrity.

The investigators of Nature were trying to preserve the reputation of physics and the rigor of peer review. Any results from any experiment has to be replicable in similar conditions in other laboratories. Usually, when retractions are ordered, it is because that didn't happen. If I drop tablets of Alka Seltzer in water in Brazil, and do it in Canada, I should still get "plop-plop-fizz-fizz." But the "odd similarity" graphs isn't that. The only differences between the two are 0.5 Gigapascals (109 Pascals, 1 Pascal = 1 Newton/meter squared = 1 N/m2), the materials under test, and the color of the graphs. Face. Plant.

Losers - The Public Trust.

"The establishment of our new government seemed to be the last **great experiment** for promoting human happiness." George Washington, January 9, 1790

As you can probably tell, I admire Carl Sagan and how he tried to popularize science communication. But Dr. Sagan, Bill Nye the Science Guy, the canceled reality series Myth Busters (that I actually LIKED) has not bridged the gap between society's obsession with spectacle, and though the previously mentioned gentlemen and television show were promoting "science as cool," it is still a discipline, it takes work and rigor to master subjects that are not part of casual conversations, nor can you "Google." There are late nights solving problems, early mornings running experiments while everyone else outside of your library or lab window seems to be enjoying college life and what it can offer.

Dr. Dias is as susceptible to Maslow's Hierarchy of Needs (physical, safety, love and belonging, esteem, and self-actualization) as anyone of us. Some humans express this need posting "selfies" or social media posts "going viral," no matter how outrageous, or the collateral damage to the non-cyber real world. Or, they like to see their names in print in journals, filling their inboxes with "related research" or "citation" emails with their names attached. There is even currency now in your research being MENTIONED in social media.


Mr. Halsey was the librarian at Fairview Elementary School in Winston-Salem, North Carolina. Everyone in my fifth grade class had to do a book report, but before we could do that, we had to pass Mr. Halsey's exam - with an 85% or better - on the Dewey Decimal System, and SHOW him in a practicum, that we could find a book that he would give you using Dewey. If you didn't pass, you didn't do the book report, and you failed English. I thankfully made an 92%, and satisfied Mr. Halsey that I wouldn't get lost in the periodicals.

We now have search engines that we can utilize via supercomputers in our hip pockets. A lot of effort to know math, physics, chemistry applied to the manufacture of semiconductors for those supercomputers instead of facilitating access to knowledge might have inadvertently manufactured a generation suffering from Dunning-Kruger. Networking those supercomputers over a worldwide web, coupled with artificial intelligence gives malevolent actors inordinate power over a captive audience of 8 billion souls.

Couple this with the falsification of data having a lease in the realm of science; it only contributes to the mistrust of institutions like the academy, like our democracy, which has been referred to since Washington as "the great experiment." If the null, and the alternate hypotheses are discarded, what pray tell, is on the other side of what we've always known?


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On-Off Superconductor...


A team of physicists has discovered a new superconducting material with unique tunability for external stimuli, promising advancements in energy-efficient computing and quantum technology. This breakthrough, achieved through advanced research techniques, enables unprecedented control over superconducting properties, potentially revolutionizing large-scale industrial applications.

Topics: Applied Physics, Materials Science, Solid-State Physics, Superconductors

Researchers used the Advanced Photon Source to verify the rare characteristics of this material, potentially paving the way for more efficient large-scale computing.

As industrial computing needs grow, the size and energy consumption of the hardware needed to keep up with those needs grows as well. A possible solution to this dilemma could be found in superconducting materials, which can reduce energy consumption exponentially. Imagine cooling a giant data center full of constantly running servers down to nearly absolute zero, enabling large-scale computation with incredible energy efficiency.

Breakthrough in Superconductivity Research

Physicists at the University of Washington and the U.S. Department of Energy’s (DOE) Argonne National Laboratory have made a discovery that could help enable this more efficient future. Researchers have found a superconducting material that is uniquely sensitive to outside stimuli, enabling the superconducting properties to be enhanced or suppressed at will. This enables new opportunities for energy-efficient switchable superconducting circuits. The paper was published in Science Advances.

Superconductivity is a quantum mechanical phase of matter in which an electrical current can flow through a material with zero resistance. This leads to perfect electronic transport efficiency. Superconductors are used in the most powerful electromagnets for advanced technologies such as magnetic resonance imaging, particle accelerators, fusion reactors, and even levitating trains. Superconductors have also found uses in quantum computing.

Scientists Discover Groundbreaking Superconductor With On-Off Switches, Argonne National Laboratory

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Pines' Demon...


Lurking for decades: researchers have discovered Pines' demon, a collection of electrons in a metal that behaves like a massless wave. It is illustrated here as an artist’s impression. (Courtesy: The Grainger College of Engineering/University of Illinois Urbana-Champaign)

Topics: Particle Physics, Quantum Mechanics, Research, Solid-State Physics, Theoretical Physics

For nearly seven decades, a plasmon known as Pines’ demon has remained a purely hypothetical feature of solid-state systems. Massless, neutral, and unable to interact with light, this unusual quasiparticle is reckoned to play a key role in certain superconductors and semimetals. Now, scientists in the US and Japan say they have finally detected it while using specialized electron spectroscopy to study the material strontium ruthenate.

Plasmons were proposed by the physicists David Pines and David Bohm in 1952 as quanta of collective electron density fluctuations in a plasma. They are analogous to phonons, which are quanta of sound, but unlike phonons, their frequency does not tend to zero when they have no momentum. That’s because finite energy is needed to overcome the Coulomb attraction between electrons and ions in a plasma in order to get oscillations going, which entails a finite oscillation frequency (at zero momentum).

Today, plasmons are routinely studied in metals and semiconductors, which have conduction electrons that behave like a plasma. Plasmons, phonons, and other quantized fluctuations are called quasiparticles because they share properties with fundamental particles such as photons.

In 1956, Pines hypothesized the existence of a plasmon which, like sound, would require no initial burst of energy. He dubbed the new quasiparticle a demon in honor of James Clerk Maxwell’s famous thermodynamic demon. Pines’ demon forms when electrons in different bands of metal move out of phase with one another such that they keep the overall charge static. In effect, a demon is the collective motion of neutral quasiparticles whose charge is screened by electrons from another band.

Demon quasiparticle is detected 67 years after it was first proposed. Edwin Cartlidg, Physics World.

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Source: Semiengineering dot com - Chiplets

Topics: Computer Science, Electrical Engineering, Materials Science, Semiconductor Technology, Solid-State Physics

Depending on who you’re speaking with at the time, the industry’s adoption of chiplet technology to extend the reach of Moore’s Law is either continuing to roll along or is facing the absence of a commercial market. However, both assertions cannot be true. What is true is that chiplets have been used to build at least some commercial ICs for more than a decade and that semiconductor vendors continue to expand chiplet usability and availability. At the same time, the interface and packaging standards that are essential to widespread chiplet adoption remain in flux.

On the positive side of this question are existence proofs. Xilinx, now AMD, has been using 2.5D chiplet technology with large silicon interposers to make FPGAs for more than a decade. The first commercial use of this packaging technology appeared back in 2011 when Xilinx announced its Virtex-7 2000T FPGA, a 2-Mgate device built from four FPGA semiconductor tiles bonded to a silicon interposer. Xilinx jointly developed this chiplet-packaging technology with its foundry, TSMC, which now offers this CoWoS (Chip-on-Wafer-on-Substrate) interposer-and-chiplet technology to its other foundry customers. TSMC customers that have announced chiplet-based products include Broadcom and Fujitsu. AMD is now five generations along the learning curve with this packaging technology, which is now essential to the continued development of bigger and more diverse FPGAs. AMD will be presenting an overview of this multi-generation, chiplet-based technology, including a status update at the upcoming Hot Chips 2023 conference being held at Stanford University in Palo Alto, California, in August.

Similarly, Intel has long been developing and using chiplet technology in its own packaged ICs. The company has been using its 2.5D EMIB (embedded multi-die interconnect bridge) chiplet-packaging technology for years to manufacture its Stratix 10 FPGAs. That technology has now spread throughout Intel’s product line to include CPUs and SoCs. The poster child for Intel’s chiplet-packaging technologies is unquestionably the company’s Ponte Vecchio GPU, which packages 47 active “tiles” – Intel’s name for chiplets – in a multi-chip package. These 47 dies are manufactured by multiple semiconductor vendors using five different semiconductor process nodes, all combined in one package using Intel’s EMIB 2.5D and 3D Foveros chiplet-packaging techniques to produce an integrated product with more than 100 billion transistors – something not currently possible on one silicon die. Intel is now opening these chiplet-packaging technologies to select customers through IFS – Intel Foundry Services – and consequently expanding the size and number of its packaging facilities.

The Chiplet’s Time Is Coming. It’s Here, Or Not. Steven Leibson, Tirias Research, Forbes

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Fractals are a never-ending pattern that you can zoom in on, and the image doesn’t change. Fractals can occur in two dimensions, like frost on a window, or in three dimensions, like tree limbs. A recent discovery from Purdue University researchers has established that superconducting images, seen above in red and blue, are actually fractals that fill a three-dimensional space and are disorder driven rather than driven by quantum fluctuations as expected. Frost and tree images by Adobe. Superconducting image (center) from "Critical nematic correlations throughout the superconducting doping range in Bi2-xPbzSr2-yLayCuO6+x" in Nature Communications. Credit: Nature Communications (2023). DOI: 10.1038/s41467-023-38249-3

Topics: Applied Physics, Civilization, Computer Modeling, Condensed Matter Physics, Materials Science, Solid-State Physics, Superconductors

Meeting the world's energy demands is reaching a critical point. Powering the technological age has caused issues globally. It is increasingly important to create superconductors that can operate at ambient pressure and temperature. This would go a long way toward solving the energy crisis.

Advancements with superconductivity hinge on advances in quantum materials. When electrons inside quantum materials undergo a phase transition, the electrons can form intricate patterns, such as fractals. A fractal is a never-ending pattern. When zooming in on a fractal, the image looks the same. Commonly seen fractals can be a tree or frost on a windowpane in winter. Fractals can form in two dimensions, like the frost on a window, or in three-dimensional space, like the limbs of a tree.

Dr. Erica Carlson, a 150th Anniversary Professor of Physics and Astronomy at Purdue University, led a team that developed theoretical techniques for characterizing the fractal shapes that these electrons make in order to uncover the underlying physics driving the patterns.

Carlson, a theoretical physicist, has evaluated high-resolution images of the locations of electrons in the superconductor Bi2-xPbzSr2-yLayCuO6+x (BSCO) and determined that these images are indeed fractal and discovered that they extend into the full three-dimensional space occupied by the material, like a tree filling space.

What was once thought of as random dispersions within the fractal images are purposeful and, shockingly, not due to an underlying quantum phase transition as expected but due to a disorder-driven phase transition.

Carlson led a collaborative team of researchers across multiple institutions and published their findings, titled "Critical nematic correlations throughout the superconducting doping range in Bi2-xPbzSr2-yLayCuO6+x," in Nature Communications.

The team includes Purdue scientists and partner institutions. From Purdue, the team includes Carlson, Dr. Forrest Simmons, a recent Ph.D. student, and former Ph.D. students Dr. Shuo Liu and Dr. Benjamin Phillabaum. The Purdue team completed their work within the Purdue Quantum Science and Engineering Institute (PQSEI). The team from partner institutions includes Dr. Jennifer Hoffman, Dr. Can-Li Song, Dr. Elizabeth Main of Harvard University, Dr. Karin Dahmen of the University of Illinois at Urbana-Champaign, and Dr. Eric Hudson of Pennsylvania State University.

Researchers discover superconductive images are actually 3D and disorder-driven fractals, Cheryl Pierce, Purdue University,

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Solid-State Cooling...


Cool stuff: the diagram shows how the temperature of the caloric material was measured. The plot in the center shows the temperature change in the sample when exposed to a magnetic field. The plot on the right shows the change in temperature when the sample is strained. (Courtesy: Peng Wu et al/Acta Materialia 237 118154)

Topics: Global Warming, Green Tech, Materials Science, Solid-State Physics, Thermodynamics

Researchers in China have shown that applying strain to a composite material using an electric field induces a large and reversible caloric effect. This novel way of enhancing the caloric effect without a magnetic field could open new avenues of solid-state cooling and lead to more energy-efficient and lighter refrigerators.

The International Institute of Refrigeration estimates that 20% of all electricity used globally is expended on vapor-compression refrigeration – which is the technology used in conventional refrigerators and air conditioners. What is more, the refrigerants used in these systems are powerful greenhouse gases that contribute significantly to global warming. As a result, scientists are trying to develop more environmentally friendly refrigeration systems.

Cooling systems can also be made from completely solid-state systems, but these cannot currently compete with vapor compression for most mainstream applications. Today, most commercial solid-state cooling systems use the Peltier effect, which is a thermoelectric process that suffers from high cost and low efficiency.

Solid-state cooling is achieved via electric field-induced strain, Hardepinder Singh, Physics World

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OIPCs and Janus...


Topics: Battery, Energy, Green Tech, Research, Solid-State Physics

Janus, in Roman religion, the animistic spirit of doorways (januae) and archways (Jani). Janus and the nymph Camasene were the parents of Tiberinus, whose death in or by the river Albula caused it to be renamed Tiber. Source: Encylopedia Britannica

Over the past decade, lithium-ion batteries have seen stunning improvements in their size, weight, cost, and overall performance. (See Physics Today, December 2019, page 20.) But they haven’t yet reached their full potential. One of the biggest remaining hurdles has to do with the electrolyte, the material that conducts Li+ ions from anode to cathode inside the battery to drive the equal and opposite flow of charge in the external circuit.

Most commercial lithium-ion batteries use organic liquid electrolytes. The liquids are excellent conductors of Li+ ions, but they’re volatile and flammable, and they offer no defense against the whisker-like Li-metal dendrites that can build up between the electrodes and eventually short-circuit the battery. Because safety comes first, battery designers must sacrifice some performance in favor of not having their batteries catch fire.

A solid-state electrolyte could solve those problems. But what kind of solid conducts ions? An ordered crystal won’t do—when every site is filled in a crystalline lattice, Li+ ions have nowhere to move to. A solid electrolyte, therefore, needs to have a disordered, defect-riddled structure. It must also provide a polar environment to welcome the Li+ ions, but with no negative charges so strong that the Li+ ions stick to them and don’t let go.

For several years, Jenny PringleMaria Forsyth, and colleagues at Deakin University in Australia have been exploring a class of materials, called organic ionic plastic crystals (OIPCs), that could fit the bill. As a mix of positive and negative ions, an OIPC offers the necessary polar environment for conducting Li+. And because the constituent ions are organic, the researchers have lots of chemical leeways to design their shapes so they can’t easily fit together into a regular lattice but are forced to adopt a disordered, Li+-permeable structure.

Two-faced ions form a promising battery material, Johanna L. Miller, Physics Today

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Pairs of Cooper Pairs...


New state of matter: The team observed electron quadruplets in this iron-based superconductor material, seen mounted for experimental measurements. (Courtesy: Vadim Grinenko, Federico Caglieris)

Topics: Condensed Matter Physics, Solid-State Physics, Superconductors

Note: I gave my research proposal last Friday. I have been answering some concerns about my proposal for the committee. I followed the outline sent to me by my advisor. I hope I've answered them sufficiently. I will post today and tomorrow; next week on Monday, Wednesday, and Friday. I tutor Calculus. For a person finished with classes, I'm extremely busy.

Cool a material below its superconducting transition temperature and you’d expect it to start conducting electricity without resistance and expelling magnetic fields. But an international group of physicists has found that a certain kind of iron-based material doped with negative charges does the opposite at around the same temperature – producing spontaneous magnetic fields and retaining resistance when chilled. The researchers say that the results point to a new state of matter in which electrons flow in correlated groups of four, rather than two.

According to the Bardeen-Cooper-Schrieffer (BCS) theory, superconductivity occurs when electrons get together to form what is known as Cooper pairs. Whereas in a vacuum two electrons would repel each other, when moving through the crystal lattice of a superconducting material, one of these particles shifts the positions of surrounding atoms to leave a small region of positive charge. This attracts the second electron to create the pair.

The creation of many such pairs yields a collective condensate, which results in frictionless electron flow. This occurs below a certain temperature – the superconducting transition temperature (Tc) – at which point atoms lack the thermal energy to break up the pairs.

Superconductor reveals new state of matter involving pairs of Cooper pairs, Edwin Cartlidge, Physics World

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Gold Anniversary...


Images are from the article, link below

Topics: Electrical Engineering, Materials Science, Nanotechnology, Solid-State Physics

It's not exactly a wedding anniversary, but it is significant.

Fifty years ago this month, Intel introduced the first commercial microprocessor, the 4004. Microprocessors are tiny, general-purpose chips that use integrated circuits made up of transistors to process data; they are the core of a modern computer. Intel created the 12 mm2 chip for a printing calculator made by the Japanese company Busicom. The 4004 had 2,300 transistors—a number dwarfed by the billions found in today’s chips. But the 4004 was leaps and bounds ahead of its predecessors, packing the computing power of the room-sized, vacuum tube-based first computers into a chip the size of a fingernail. In the past 50 years, microprocessors have changed our culture and economy in unimaginable ways.

The microprocessor turns 50, Katherine Bourzac, Chemical & Engineering News

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