BLOGS

An RNA-making molecule crystallizes on magnetite, which can bias the process toward a single chiral form. S. FURKAN OZTURK

Topics: Biology, Biotechnology, Chemistry, Magnetism, Materials Science

In 1848, French chemist Louis Pasteur discovered that some molecules essential for life exist in mirror-image forms, much like our left and right hands. Today, we know biology chooses just one of these “chiral” forms: DNA, RNA, and their building blocks are all right-handed, whereas amino acids and proteins are all left-handed. Pasteur, who saw hints of this selectivity, or “homochirality,” thought magnetic fields might somehow explain it, but its origin has remained one of biology’s great mysteries. Now, it turns out Pasteur may have been onto something.

In three new papers, researchers suggest magnetic minerals common on early Earth could have caused key biomolecules to accumulate on their surface in just one mirror image form, setting off positive feedback that continued to favor the same form. “It’s a real breakthrough,” says Jack Szostak, an origin of life chemist at the University of Chicago who was not involved with the new work. “Homochirality is essential to get biology started, and this is [a possible]—and I would say very likely—solution.”

Chemical reactions are typically unbiased, yielding equal amounts of right- and left-handed molecules. But life requires selectivity: Only right-handed DNA, for example, has the correct twist to interact properly with other chiral molecules. To get [life], “you’ve got to break the mirror, or you can’t pull it off,” says Gerald Joyce, an origin of life chemist and president of the Salk Institute for Biological Studies.

Over the past century, researchers have proposed various mechanisms for skewing the first biomolecules, including cosmic rays and polarized light. Both can cause an initial bias favoring either right- or left-handed molecules, but they don’t directly explain how this initial bias was amplified to create the large reservoirs of chiral molecules likely needed to make the first cells. An explanation that creates an initial bias is a good start but “not sufficient,” says Dimitar Sasselov, a physicist at Harvard University and a leader of the new work.

‘Breakthrough’ could explain why life molecules are left- or right-handed, Robert F. Service, Science.org.

FIG. 1. (a) Sketches of the excitations of surface plasmons polaritons - SPP (top), localized surface plasmons - LSP (middle), and magnetic plasmons - MP (bottom). All these excitations are associated with a collective motion of surface charges under light illumination. (b) Diagram of MP-based plasmonic nanostructures used for fundamental studies and their applications in various research fields.

Topics: Electromagnetism, Magnetism, Metamaterials, Nanoclusters, Nanomaterials, Plasmonic Nanostructures

Abstract

The magnetic response of most natural materials, characterized by magnetic permeability, is generally weak. Particularly in the optical range, the weakness of magnetic effects is directly related to the asymmetry between electric and magnetic charges. Harnessing artificial magnetism started with a pursuit of metamaterial design exhibiting magnetic properties. A plasmonic nanostructure called split-ring resonators gave the first demonstration of artificial magnetism. Engineered circulating currents form magnetic plasmons, acting as the source of artificial magnetism in response to external electromagnetic excitation. In the past two decades, magnetic plasmons supported by plasmonic nanostructures have become an active topic of study. This Perspective reviews the latest studies on magnetic plasmons in plasmonic nanostructures. A comprehensive summary of various plasmonic nanostructures supporting magnetic plasmons, including split-ring resonators, metal–insulator–metal structures, metallic deep groove arrays, and plasmonic nanoclusters, is presented. Fundamental studies and applications based on magnetic plasmons are discussed. The formidable challenges and the prospects of the future study directions on developing magnetic plasmonic nanostructures are proposed.

Magnetic plasmons in plasmonic nanostructures: An overview

Artist's representation of the circular phonons. (Courtesy: Nadja Haji and Peter Baum, University Konstanz)

Topics: Applied Physics, Lasers, Magnetism, Materials Science, Phonons

When a magnetic material is bombarded with short pulses of laser light, it loses its magnetism within femtoseconds (10^–15 seconds). The spin, or angular momentum, of the electrons in the material, thus disappears almost instantly. Yet all that angular momentum cannot simply be lost. It must be conserved – somewhere.

Thanks to new ultrafast electron diffraction experiments, researchers at the University of Konstanz in Germany have now found that this “lost” angular momentum is in fact transferred from the electrons to vibrations of the material’s crystal lattice within a few hundred femtoseconds. The finding could have important implications for magnetic data storage and for developments in spintronics, a technology that exploits electron spins to process information without using much power.

In a ferromagnetic material, magnetism occurs because the magnetic moments of the material’s constituent atoms align parallel to each other. The atoms and their electrons then act as elementary electromagnets, and the magnetic fields are produced mainly by the spin of the electrons.

Because an ultrashort laser pulse can rapidly destroy this alignment, some scientists have proposed using such pulses as an off switch for magnetization, thereby enabling ultra-rapid data processing at frequencies approaching those of light. Understanding this ultrafast demagnetization process is thus crucial for developing such applications as well as for better understanding the foundations of magnetism.

Researchers find ‘lost’ angular momentum, Isabelle Dumé, Physics World

Magnetic prosthetic: A magnetic sensing array enables a new tissue tracking strategy that could offer advanced motion control in artificial limbs. (Courtesy: MIT Media Lab/Cameron Taylor/Vessel Studios)

Topics: Biotechnology, Magnetism, Materials Science, Medicine, Nanotechnology, Robotics

Cultural reference: The Six Million Dollar Man, NBC

In recent years, health and fitness wearables have gained popularity as platforms to wirelessly track daily physical activities, by counting steps, for example, or recording heartbeats directly from the wrist. To achieve this, inertial sensors in contact with the skin capture the relevant motion and physiological signals originating from the body.

As wearable technology evolves, researchers strive to understand not just how to track the body’s dynamic signals, but also how to simulate them to control artificial limbs. This new level of motion control requires a detailed understanding of what is happening beneath the skin, specifically, the motion of the muscles.

Skeletal muscles are responsible for almost all movement of the human body. When muscle fibers contract, the exerted forces travel through the tendons, pull the bones, and ultimately produce motion. To track and use these muscle contractions in real-time and with high signal quality, engineers at the Massachusetts Institute of Technology (MIT) employed low-frequency magnetic fields – which pass undisturbed through body tissues – to provide accurate and real-time transcutaneous sensing of muscle motion. They describe their technique in Science Robotics.

Magnetic beads inside the body could improve control of bionic limbs, Raudel Avila is a student contributor to Physics World

Topics: Economics, Futurism, Magnetism, Transportation

In the desert just north of Las Vegas, a long white metal tube sits at the base of the mountains, promising to one day revolutionize travel.

That is where Virgin Hyperloop, whose partners include Richard Branson's Virgin Group, is developing the technology for passenger pods that will hurtle at speeds of up to 750 miles an hour (1,200 kph) through almost air-free vacuum tunnels using magnetic levitation.

"It will feel like an aircraft at take-off and once you're at speed," said co-founder and Chief Executive Josh Giegel, who gave Reuters an exclusive tour of the pod used in its November test run, where it was propelled along a 500 meter (1,640 ft.) tunnel.

"You won't even have turbulence because our system is basically completely able to react to all that turbulence. Think noise-canceling but bump-canceling, if you will."

Virgin Hyperloop shows off the future: mass transport in floating magnetic pods, Reuters

Illustration showing the atomic tip of a scanning tunneling microscope while probing a metal surface with a cobalt atom positioned on top. A characteristic dip in the measurement results is found on surfaces made of copper as well as silver and gold. Courtesy: Forschungszentrum Jülich

Topics: Magnetism, Materials Science, Nanotechnology

A new type of quasiparticle – dubbed the “spinaron” by the scientists who discovered it – could be responsible for a magnetic phenomenon that is usually attributed to the Kondo effect. The research, which was carried out by Samir Lounis and colleagues at Germany’s Forschungszentrum Jülich, casts doubt on current theories of the Kondo effect and could have implications for data storage and processing based on structures such as quantum dots.

The electrical resistance of most metals decreases as the temperature drops. Metals containing magnetic impurities, however, behave differently. Below a certain threshold temperature, their electrical resistance increases rapidly and continues to increase as the temperature drops further. First spotted in the 1930s, this phenomenon became known as the Kondo effect after the Japanese theoretical physicist Jun Kondo published an explanation for it in 1964.

New quasiparticle may mimic Kondo-effect signal, Isabelle Dumé, Physics World

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Topics: Atomic Physics, Magnetism, Superconductors

Web Elements: Uranium Tritelluride

Exotic superconducting state lurks at an astonishingly high magnetic field
Johanna L. Miller, Physics Today