A technique known as ghost imaging has been adapted so that an object can be imaged by discarding all photons that interact with it.
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Quantum sensor could measure how Earth drags spacetime
Einstein’s theory of general relativity describes gravity as the bending of spacetime, a mathematical model that combines three-dimensional space and time into a single, four-dimensional continuum. The theory also predicts that a rotating object, such as Earth, slightly drags the surrounding spacetime as it rotates, a phenomenon known as frame-dragging.
Researchers at the University of California, Berkeley (UC Berkeley), the Austrian Academy of Sciences and the California Institute of Technology (Caltech) recently introduced the idea of a quantum sensor that could measure this tiny effect in a laboratory setting. Their proposed experiment, described in a paper published in Physical Review Letters, would use helium cooled until it enters a special phase known as the superfluid state inside a gyrometer, an instrument that measures rotation.
“The inspiration for this project came when Birgitta Whaley and I were visiting Markus Aspelmeyer at the Institute for Quantum Optics and Quantum Information (IQOQI) in Vienna, Austria, during a sabbatical of Birgitta,” Kai-Isaak Ellers, first author of the paper, told Phys.org.
Why tightly confined water’s response to electric fields depends on direction
Using an advanced new mathematical model, a pair of physicists in Belgium has revealed the origins of an unusual, direction-dependent effect found in water confined to a narrow gap between two plates. Through research published in Physical Review Letters, Mehdi Neek-Amal and Francois Peeters at the University of Antwerp showed how two drastically different dielectric responses in this water emerge from the natural bonding behavior of its molecules.
Dielectric materials are made up of molecules with built-in electric dipoles: a positive charge at one end and a negative charge at the other. When exposed to an electric field, these dipoles rotate so that their positive ends point in the direction of the applied field and their negative ends in the opposite direction. This polarization creates an internal electric field within the material that partially cancels out the applied field.
In pure water, the dielectric effect emerges due to the tendency of oxygen atoms to pull electrons away from the hydrogen atoms they bond to covalently, creating a dipole across the chevron-shaped molecule. Under ordinary conditions, this creates hydrogen-bonding networks, where the positive hydrogen atoms of one molecule are attracted electrostatically to the negative oxygen atom at the tip of a neighboring chevron.
Single 2D crystal transforms into transistor with built-in insulation and electrical contacts
A transistor normally requires several fundamentally different materials—a semiconductor to carry current, an insulating dielectric to control it and metallic contacts through which current enters and leaves. Integrating all of these components becomes increasingly difficult as semiconductor devices approach the atomic scale.
A research team led by Director Jo Moon-Ho of the Center for Van der Waals Quantum Solids within the Institute for Basic Science (IBS) has now demonstrated a fundamentally different approach. Instead of fabricating the semiconductor, dielectric and contact materials separately and then assembling them into a device, the researchers started from a single layered crystal and chemically converted selected atomic layers and regions into the different materials needed for a working transistor. The work is published in the journal Science.
Mini brain organoids ‘read’ braille in key step toward biohybrid computing
Could computers include tiny brain organoids one day? The human brain is an incredibly energy-efficient computer, and silicon processors that try to imitate it achieve huge energy savings over traditional processors. Now scientists are experimenting with using organoids modeled on the human forebrain to develop energy-efficient biohybrid computing.
A crucial first step toward this is learning whether the organoids can receive and relay signals reliably, which a Bristol-based team of researchers investigated using braille letters. They found that teams of three brain organoids produced signals that accurately corresponded to different letters 83% of the time.
“We can take information from a real tactile sensor, turn it into a form that a living neural network can receive, and then recover meaningful information from the organoid response,” said Tianyi Liu, a Ph.D. candidate at Bristol University and first author of the article in Frontiers in Artificial Intelligence.
AI agents develop their own ‘artificial natural language’ to communicate about complex data
Researchers from the VUB’s Artificial Intelligence Lab and the University of Namur (UNamur) demonstrate in a new large-scale study how autonomous AI systems can spontaneously develop a functional, shared language without human intervention.
Unlike large language models such as ChatGPT, which memorize existing human language, these AI agents construct their own communication system, directly rooted in their specific sensors and environment.
This discovery represents a breakthrough for communication between autonomous systems, such as self-driving cars, robots and industrial sensors.
Chemical fine-tuning lifts perovskite LEDs to 37% efficiency
Chemists developed a way to significantly improve the performance of light-emitting diodes (LEDs) made with perovskite. The journal Nature published the advancement in these hybrid LEDs, which hold potential for a range of uses, including biomedical sensing, low-light imaging and automated facial recognition.
Most previous work in perovskite LEDs has yielded rates of quantum efficiency—the ability to convert electricity to light—within a range of 20–30%.
“Our discovery leads to an efficiency rate closer to 40%. That’s a big jump,” says Letian Dou, senior author of the paper and professor of chemistry at Emory University.
Tiny chip uses ultrasound-powered microbubbles to steer fluid flow in real time
Bubbles can be useful tools for microscopic robots, helping them move, steer, create flows of liquid and perform other functions. But designs based on trapping a bubble, a common approach, are unwieldy and unpredictable because bubbles can be hard to catch and control.
“Why are we trying to trap these bubbles?” said Itai Cohen, the Josephson Family Professor of physics in the College of Arts and Sciences (A&S). “Let’s just make them where we want them, when we want them.”
Researchers in Cohen’s lab have developed a way to create and direct microbubbles on demand, without requiring trapping. Set within a 3-millimeter area on a chip, the device produces hydrogen gas bubbles on a grid of electrodes, then powers the bubbles up with acoustic energy through ultrasound. Bubbles resonating on the electrodes can work alone, in pairs or in larger groups to create and direct flows of fluid.
Molecular snapshots reveal how viral enzymes switch between inserting and removing DNA
Bacteriophages, or viruses that infect bacteria, have a fiendishly simple purpose in life: attach to a bacterial cell, inject their DNA and then use the host’s genetic machinery to reproduce. In doing so, they may have evolved some of the most efficient gene-editing tools ever seen in nature.
New research by scientists at the University of Chicago shows how bacteriophages (“phages” for short) use a special class of enzymes to recognize specific DNA sequences in their host and insert large stretches of their own DNA with remarkable precision.
The study also shows how these enzymes can switch directions and remove the phage DNA without a trace, offering new insights that could help scientists develop more precise tools for genome engineering and synthetic biology.
In plants, sense of time is connected with sense of danger
Salty soil is a growing threat to crops worldwide. Hotter, drier weather has increased evaporation rates, drawing moisture from the soil and leaving behind concentrated mineral salts. At the same time, water shortages are forcing farmers to irrigate using water from lower-quality, saline or recycled sources. Scientists estimate that around half of the world’s irrigated farmland is now affected by salinity to some degree.
A new study from Washington University in St. Louis reveals how a plant’s internal clock helps it to respond to dangerous salts in its environment. Understanding how plants time their defenses against salt could eventually help scientists develop crops that hold up better against salt stress.
The research, published Oct. 14 in Science Advances, was led by biologist Xuehua Zhong, the Dean’s Distinguished Professorial Scholar in WashU Arts & Sciences, and WashU postdoctoral fellow Wenwen Tian, an expert in circadian biology.