Lifeboat Foundation

A venerable strategy for approximating a system’s ground states has now been extended to accommodate its excited states.

Density-functional theory (DFT) owes its name and utility to its central insight: that a potential’s influence on a system of interacting electrons can be expressed in terms of the electrons’ density. Existing models restrict DFT to ground states and exclude excited states. But now Tim Gould of Griffith University, Australia, and his collaborators have found a way to overcome the restriction [1].

At the heart of DFT are exchange-correlation models, which simplify the treatment of electrons’ behavior by using certain limiting cases. This simplification allows DFT to simulate ground states of large electronic systems. A generalization of the theory, called ensemble DFT, can cope with excited states, but this theory’s more complex exchange-correlation models make large systems computationally intractable. Gould and his collaborators discovered that when the electron density is sufficiently low, these complications vanish and the models for dealing with excited states revert to being as simple as those used for regular DFT. Then, regular DFT suffices. At the other extreme—when electron density is high—complications are simplified to the point that exact solutions can be obtained.

Another part of that wariness arises because, to date, no one has independently reproduced Dias’ team’s results. This lack of verification was raised by Jorge Hirsch of the University of California, San Diego, in the last talk of the session in which Dias and his team spoke. Hirsch argued that those claiming to have created high-temperature superconducting hydrides suffered from “confirmation bias,” cherry-picking evidence to support their agenda. (Hirsch has been an outspoken critic of Dias’ work.) As the last question of the session, Dias asked Hirsch, “Could you also have confirmation bias?” “Maybe,” Hirsch replied.

After the session, a few attending researchers—all collaborators of Dias—spoke with Physics Magazine, telling us that they disagreed with Hirsch’s cherry-picking conclusion. One of them, Russell Hemley of the University of Illinois Chicago confirmed Pasan’s claim that they have replicated the 2020 carbonaceous sulfur hydride—as reported in an arXiv paper that the team recently posted [3].

Dias’ group still needs to more precisely characterize NLH’s chemical composition, Pasan said. The samples also appear to consist of two phases, an observation that they need to investigate. Ultimately, they plan to innovate upon this material to create a superconductor at ambient pressure and temperature conditions, a goal that Pasan said he thinks is feasible. But extraordinary claims require extraordinary evidence, and the community has much of the latter still to gather.

The ultimate miniature electronic device may be one that manipulates individual electrons with subnanometer and subfemtosecond precision. The past few decades have seen immense progress in the control of ultrafast electronic processes, including in the context of vacuum nanoelectronics, where electrons travel from a nanoscale emitter to a target electrode through a vacuum. Now Hirofumi Yanagisawa at the Japan Science and Technology Agency and colleagues have taken an important step toward optimal spatial control by using the orbitals of a single molecule to shape its electron emission (Fig. 1) [1]. The approach offers the prospect of building highly controllable electron emitters, but also of furthering our understanding of the role of molecular orbitals in the electronic structure of solids.

Fundamental to achieving extreme control over electron emission is defining the spot from which electrons are ejected from the emitter. One approach is to physically shape the material of the emitter into the desired spot pattern. Doing that at the subnanometer scale would entail significant material-and fabrication-related challenges, however. Instead, Yanagisawa and colleagues have demonstrated the clever idea of using the inherent electronic structure of a molecule to route the electrons for emission. In essence, the molecular orbitals are used as a spatial filter to control the emission pattern.

The team’s work grows out of two broad areas of investigation that have progressed significantly over the past few decades. One of these involves the study of femto-and attosecond electron dynamics and the creation of ultrafast electron sources, exemplified by the 2006 demonstration of tight spatial control over femtosecond electron pulses through emission from a nanoscale metallic tip [2– 8]. The second is the study of electron emission patterns originating from molecular structures and nanostructures. Examples include patterns corresponding to the tip structures of nanotubes and nanowires, which change as the tip evolves during nanotube growth [9– 11]. It is by combining the techniques of ultrafast emission and emission microscopy that Yanagisawa and colleagues have demonstrated that the emission patterns can be directly linked to specific molecular orbitals.

Prompt engineering enables researchers to generate customized training examples for lightweight “student” models.

The thyroid is a small, butterfly-shaped gland at the base of the neck. It’s responsible for the hormones that control your heart rate, blood pressure, temperature and metabolism.

When thyroid cells grow abnormally, they can cause thyroid cancer. But because symptoms are vague and may mimic other less-serious conditions, it’s possible you could have thyroid cancer for months or even years without knowing it.

Thyroid cancer surgeon Nancy Perrier, M.D., explains how thyroid cancer can go unnoticed – and what you can do to catch it early when it’s easiest to treat.

The potential for supply constraints also concerns industry analysts. For example, McKinsey analysts have warned that limited AAV vector capacity could delay the commercialization of new gene therapies, particularly those intended for larger patient populations.

Last March, a McKinsey article stated, “The majority of early viral-vector-based therapeutics were developed within the context of rare diseases. [Only small] quantities of viral vectors were required, particularly as most therapies were still in the clinical stage of development. Now, with the shift beyond ultrarare indications, viral vector manufacturing requires rapid expansion to be able to address these diseases in the commercial space.”

The Last of Us may be more real than you think. The spread of fungal pathogens in humans and other species are a disaster waiting to happen.

Robot grippers made from soft plastics will melt in the heat, but a wooden alternative can do the job just fine.

By Alex Wilkins

The sense of touch may soon be added to the virtual gaming experience, thanks to an ultrathin wireless patch that sticks to the palm of the hand. The patch simulates tactile sensations by delivering electronic stimuli to different parts of the hand in a way that is individualized to each person’s skin.

Developed by researchers at City University of Hong Kong (CityU) with collaborators and described in the journal Nature Machine Intelligence (“Encoding of tactile information in hand via skin-integrated wireless haptic interface”), the patch has implications beyond virtual gaming, as it could also be used for robotics surgery and in prosthetic sensing and control.

‘Haptic’ gloves, that simulate the sense of touch, already exist but are bulky and wired, hindering the immersive experience in virtual and augmented reality settings. To improve the experience, researchers led by CityU biomedical engineer Yu Xinge developed an advanced, wireless, haptic interface system called ‘WeTac’.