AsianScientist (Jun. 9, 2020) – Researchers in Singapore have shown that a single atom can function as either an engine or a fridge. These findings, published in npj Quantum Information, pave the way for future computers and fuel cells to control energy flows.

Engines and refrigerators are both machines described by thermodynamics, a branch of science that tells us how energy moves within a system and how we can extract useful work. A classical engine turns energy into useful work. A refrigerator does work to transfer heat, reducing the local temperature. They are, in some sense, opposites.

While previous research has shown that a single atom can act as a heat engine, the present study shows that single atoms can also act as mini refrigerators, converting energy in the opposite direction.

“Think about how your computer or laptop has a lot of things inside it that heat up. Today you cool that with a fan that blows air. In nanomachines or quantum computers, small devices that do cooling could be something useful,” said Associate Professor Dario Poletti from the Singapore University of Technology and Design, Singapore.

Using a single barium atom, the researchers used lasers to move one of the atom’s electrons between two energy levels as part of a cycle, causing some energy to be pushed into the atom’s vibrations. Just as a car engine consumes petrol to both move pistons and charge up its battery, the atom uses energy from lasers as fuel to increase its vibrating motion. The atom’s vibrations thus act like a battery, storing energy that can be extracted later.

By rearranging the cycle, the researchers were able to make the atom act like a fridge, removing energy from the vibrations. In either mode of operation, quantum effects showed up in correlations between the atom’s electronic states and vibrations.

“At this scale, the energy transfer between the engine and the load is a bit fuzzy. It is no longer possible to simply do work on the load, you are bound to transfer some heat,” said Poletti.

To get around the problem, the team used a barium atom from which an electron (a negative charge) is removed. This makes the atom positively charged, so it can be more easily held still inside a metal chamber by electrical fields. The atom was then zapped with lasers to move it through a four-stage cycle.

After applying several cycles, the researchers measured the atom’s vibration to determine how much vibrational energy was present at the end. They could see the vibrational energy increasing when the atom was zapped with an engine cycle, and decreasing when the zaps followed the fridge cycle.

“Loosely speaking, we’ve designed a little machine that creates entropy as it is filled up with free energy, much like kids when they are given too much sugar,” said study first author, PhD student Noah Van Horne.

The article can be found at: Van Horne et al. (2020) Single-atom Energy-conversion Device with a Quantum Load.

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Source: National University of Singapore.
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AsianScientist (Jun. 9, 2020) – An intriguing study from China has found evidence for the oldest known parasite–host relationship in the fossil record. These findings suggest that parasitism may have existed shortly after the Cambrian explosion, which happened approximately 541 million years ago.

Brachiopods are small shell-like marine animals that resemble bivalve mollusks. There are currently approximately 450 species of brachiopods living, but over 12,000 species are known from the fossil record.

In a study published recently in Nature Communications, Prof. Zhang Zhifei from China’s Northwest University and colleagues analyzed a fossil population of the Cambrian brachiopod Neobolus wulongqingensis discovered in Yunnan, China, dating from approximately 512 million years ago.

Many of the brachiopods were encrusted with a tube-dwelling organism on the outside of their shells. Brachiopods that were encrusted with tubes were significantly smaller and the tubes were aligned with the brachiopod’s own feeding currents.

The researchers suggest that the tube-dwelling organism was a kleptoparasite, as it likely diverted the ancient brachiopod’s food to itself and reduced the host’s fitness.

“Kleptoparasitism is a form of competition, where food that is either already in the possession of the host or which the host has expended energy on obtaining and capture is imminent, is stolen by the parasite,” the authors write.

Parasitic interactions are difficult to document in the fossil record because most inferences have to be made based on appearance. Here, the authors have assembled rare evidence of not only the appearance of parasitism, but a cost of parasitism as well.

“Our analyses demonstrate that the tube-dwelling organism directly impinges upon the biological fitness of the host, supporting the assertion that the encrusting tube-dwelling organisms are parasitic, rather than being either mutualistic or commensal with the brachiopod host,” the authors write.

The article can be found at: Zhang et al. (2020) An Encrusting Kleptoparasite-host Interaction From the Early Cambrian.

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Source: Nature; Illustration: Rebecca Gelernter/Near Bird Studios.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.