Émile Torres on existential risks, escatology, teleology and transhumanism: “One of the risks of the future is Longtermism itself.”
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Graphene measurements reveal energy-loss and quantum-coherence exponents diverge under gate control
Scientists have shown that the two exponents (inelastic scattering exponent and dephasing exponent) commonly used to describe electron scattering in graphene do not necessarily follow the same behavior. Using gated epitaxial graphene, a multi-institutional team of researchers independently extracted the two exponents through current-heating measurements and weak-localization analysis. The contrasting gate-voltage dependence provides evidence that energy relaxation and loss of quantum phase coherence can be governed by different microscopic processes.
The team was led by Dr. Wei-Chen Lin at National Taiwan University and collaborating institutions. Their study, published in Carbon, challenges a long-standing assumption that the exponents used to characterize these two processes should be equivalent.
An electron in a solid can lose energy through inelastic scattering, while quantum coherence can be lost when the phase relationship between electron wave functions is disrupted. These two phenomena are closely related, but they do not necessarily provide the same information. In this study, scientists used epitaxial graphene grown on silicon carbide and controlled its carrier density with a gate voltage.
Could negative mass exist and be observed?
Unlike electric charge, as far as we know all mass is positive, and positive masses attract one another. Could negative mass exist, and if so, what would be the ramifications?
Antigravity between a positive mass and a hypothetical negative mass has received a fair bit of attention in both physics and science fiction over the years. For example, in 1901’s “First Men in the Moon” author H. G. Wells imagines a substance he calls “cavorite” which creates a negative force of gravity and thus acts as a gravity shield. In Newton’s theory of gravity, negative mass would effectively appear as his same equation but with the gravitational constant G replaced by-G. But Einstein’s version of gravity, general relativity, is not so kind, and does not seem to consistently allow anti-gravity.
In a new paper in Physics of the Dark Universe, Shin’ichi Nojiri from Japan and S.D. Odintsovc from Spain dig deeper into the possibility of negative mass objects (NMOs) and conclude that the idea may not be as exotic as is thought. Using theoretical tools, they show that negative mass “does not always lead to any inconsistency.”
Scientists build world’s most accurate atomic clock
Take a second and turn it into trillions of moments. Measure each one. That’s how precisely an atomic clock at Singapore’s Centre for Quantum Technologies (CQT) keeps time—and with record-setting accuracy, according to results published in Nature on Sept. 23.
“I am confident that what we have now is the most accurate clock in the world,” says team leader Murray Barrett, a CQT principal investigator and associate professor in the Department of Physics at the National University of Singapore.
The researchers base their claim on measurements showing that their atomic clock, built from the element lutetium, outperforms previous record holders built from different elements.
Quantum device simulates matter popping into existence
A research team led by faculty at the Duke Quantum Center (DQC) has observed string-breaking dynamics related to particle-antiparticle formation on a quantum simulator, among the first such observations in quantum physics.
The approach, described in the journal Nature Physics, shows that trapped-ion quantum computers can be used to probe fundamental questions about the universe. The experiment emulates string-breaking, a phenomenon in which two connected fundamental building blocks of matter stretch apart, building up enough energy that new particles “pop into existence” when the connection snaps.
“Quantum computer simulations provide the best platform to investigate complex questions like matter formation, short of having witnessed the Big Bang itself,” said Christopher Monroe, the Gilhuly Family Presidential Distinguished Professor of Electrical and Computer Engineering and Physics at Duke, who led the research.
New robotic hand can walk, press keys and move objects on its own
For many of us, the last—and only—time we’ve seen a walking hand was Thing in “The Addams Family” movies or TV series. Now there’s another. Engineers from the Soft Robotics Lab at ETH Zurich have adapted an off-the-shelf detached robotic hand so it can crawl across different surfaces, balance and interact with its environment.
But this is no sci-fi gimmick. Fully mobile robotic hands could be useful in hard-to-reach spaces. “A robotic hand with its own mobility could operate in confined workspaces without requiring the arm that normally carries it to follow,” says the research team.
Ancient genome function persists despite frequent mutations, centromere study shows
Every time a cell divides, its chromosomes must be distributed correctly between the two daughter cells. Central to this process is the centromere, a specialized region of the chromosome. The centromere serves as the attachment site for the cellular machinery that pulls the chromosomes apart.
Centromeres thus perform an essential function in cell division that emerged very early in eukaryotic evolution. Remarkably, although this function has been retained over almost 2 billion years of evolution, the DNA sequences underlying centromeres have evolved at an extraordinarily rapid rate. An international team led by Dr. Korbinian Schneeberger, a professor and head of the Institute of Crop Biology at HHU, has now discovered how relatively small mutations can give rise to the enormous differences between centromeres. Their paper is published in Nature.
While the fundamental function of centromeres is highly conserved, their DNA sequences are not: Centromeres can differ dramatically between species and even between individuals of the same species. This apparent contradiction is known in biology as the “centromere paradox” and raises the question of how a structure that has retained such an ancient function can contain DNA that changes so rapidly.
Fluorescence timing identifies eight proteins in one cell with a single staining step
An international collaboration led by the University Medical Center Göttingen (UMG), Germany, has developed a labeling method that distinguishes fluorescent labels not by color but by how long it takes a dye to emit fluorescence. This makes it possible to visualize eight different proteins in a cell simultaneously in a single step using standard microscopes. The results have been published in the journal ACS Nano.
Fluorescence microscopy is an important method in biomedical research that allows researchers to visualize specific proteins and cellular structures. Researchers typically use antibodies carrying fluorescent dyes to mark the proteins they want to study. When excited, the dyes fluoresce, and a microscope detects the light they emit. The problem: Conventional microscopes can detect only three or four colors at a time—for example, blue/purple, green, yellow/orange and red—so only that many proteins can be distinguished simultaneously.
An international research team led by Dr. Felipe Opazo, a research group leader at the Department of Neuro-and Sensory Physiology and the Center for Biostructural Imaging of Neurodegeneration (BIN) at the University Medical Center Göttingen (UMG), together with Dr. Roman Tsukanov, a postdoctoral researcher at the Third Institute of Physics at the University of Göttingen, has now opened up a second dimension. Alongside color, the researchers use a property rarely exploited until now: fluorescence lifetime, the few billionths of a second a dye glows after being excited by laser light.