Novel Laminated Nanostructure Gives Steel Bone-like Resistance To Fracturing Under Repeated Stress

Novel laminated nanostructure gives steel bone-like resistance to fracturing under repeated stress

Metal fatigue can lead to abrupt and sometimes catastrophic failures in parts that undergo repeated loading, or stress. It’s a major cause of failure in structural components of everything from aircraft and spacecraft to bridges and powerplants. As a result, such structures are typically built with wide safety margins that add to costs.

Now, a team of researchers at MIT and in Japan and Germany has found a way to greatly reduce the effects of fatigue by incorporating a laminated nanostructure into the steel. The layered structuring gives the steel a kind of bone-like resilience, allowing it to deform without allowing the spread of microcracks that can lead to fatigue failure.

The findings are described in a paper in the journal Science by C. Cem Tasan, the Thomas B. King Career Development Professor of Metallurgy at MIT; Meimei Wang, a postdoc in his group; and six others at Kyushu University in Japan and the Max Planck Institute in Germany.

“Loads on structural components tend to be cyclic,” Tasan says. For example, an airplane goes through repeated pressurization changes during every flight, and components of many devices repeatedly expand and contract due to heating and cooling cycles. While such effects typically are far below the kinds of loads that would cause metals to change shape permanently or fail immediately, they can cause the formation of microcracks, which over repeated cycles of stress spread a bit further and wider, ultimately creating enough of a weak area that the whole piece can fracture suddenly.

The Myth of Prometheus

Before the creation of humanity, the Greek gods won a great battle against a race of giants called the Titans. Most Titans were destroyed or driven to the eternal hell of Tartarus. But the Titan Prometheus, whose name means foresight, persuaded his brother Epimetheus to fight with him on the side of the gods.

As thanks, Zeus entrusted the brothers with the task of creating all living things. Epimetheus was to distribute the gifts of the gods among the creatures. To some, he gave flight; to others, the ability to move through water or race through grass. He gave the beasts glittering scales, soft fur, and sharp claws.

Meanwhile, Prometheus shaped the first humans out of mud. He formed them in the image of the gods, but Zeus decreed they were too remain mortal and worship the inhabitants of Mount Olympus from below. Zeus deemed humans subservient creatures vulnerable to the elements and dependent on the gods for protection. However, Prometheus envisioned his crude creations with a greater purpose. So when Zeus asked him to decide how sacrifices would be made, the wily Prometheus planned a trick that would give humans some advantage. He killed a bull and divided it into two parts to present to Zeus. On one side, he concealed the succulent flesh and skin under the unappealing belly of the animal. On the other, he hid the bones under a thick layer of fat. When Zeus chose the seemingly best portion for himself, he was outraged at Prometheus’s deception.

Fuming, Zeus forbade the use of fire on Earth, whether to cook meat or for any other purpose. But Prometheus refused to see his creations denied this resource. And so, he scaled Mount Olympus to steal fire from the workshop of Hephaestus and Athena. He hid the flames in a hollow fennel stalk and brought it safely down to the people. This gave them the power to harness nature for their own benefit and ultimately dominate the natural order.

With fire, humans could care for themselves with food and warmth. But they could also forge weapons and wage war. Prometheus’s flames acted as a catalyst for the rapid progression of civilization. When Zeus looked down at this scene, he realized what had happened. Prometheus had once again wounded his pride and subverted his authority.

Furious, Zeus imposed a brutal punishment. Prometheus was to be chained to a cliff for eternity. Each day, he would be visited by a vulture who would tear out his liver and each night his liver would grow back to be attacked again in the morning. Although Prometheus remained in perpetual agony, he never expressed regret at his act of rebellion. His resilience in the face of oppression made him a beloved figure in mythology. He was also celebrated for his mischievous and inquisitive spirit, and for the knowledge, progress, and power he brought to human hands.

He’s also a recurring figure in art and literature. In Percy Bysshe Shelley’s lyrical drama “Prometheus Unbound,” the author imagines Prometheus as a romantic hero who escapes and continues to spread empathy and knowledge. Of his protagonist, Shelley wrote, “Prometheus is the type of the highest perfection of moral and intellectual nature, impelled by the purest and the truest motives to the best and noblest ends.” His wife Mary envisaged Prometheus as a more cautionary figure and subtitled her novel “Frankenstein: The Modern Prometheus.” This suggests the damage of corrupting the natural order and remains relevant to the ethical questions surrounding science and technology today. As hero, rebel, or trickster, Prometheus remains a symbol of our capacity to capture the powers of nature, and ultimately, he reminds us of the potential of individual acts to ignite the world.

From the TED-Ed Lesson The myth of Prometheus - Iseult Gillespie

Animation by Léa Krawczyk ( @lea–krawczyk )

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New ways to mass produce human neurons for studying neuropsychiatric disorders

Scientists from Singapore have streamlined the process of using human stem cells to mass produce GABAergic neurons (GNs) in the laboratory. This new protocol provides scientists with a robust source of GNs to study many psychiatric and neurological disorders such as autism, schizophrenia, and epilepsy, which are thought to develop at least in part due to GN dysfunction.

GNs are inhibitory neurons that reduce neuronal activation, and make up roughly 20 per cent of the human brain. They work alongside excitatory neurons (ENs) to ensure balanced neural activity for normal brain function. The coordinated interplay between GNs and ENs orchestrate specific activation patterns in the brain, which are responsible for our behaviour, emotions, and higher reasoning. Functional impairment of GNs results in imbalanced neural activity, thereby contributing to the symptoms observed in many psychiatric disorders.

The availability of high quality, functional human GN populations would facilitate the development of good models for studying psychiatric disorders, as well as for screening drug effects on specific populations of neurons. Scientists worldwide have been hard at work trying to generate a consistent supply of GNs in the laboratory, but have been faced with many challenges. Protocols involving multiple complex stages, poor yield, and requiring a long time to generate mature and functional GNs are just some of the limitations encountered.

Many of these limitations have now been overcome by the development of a rapid and robust protocol to generate GNs from human pluripotent stem cells (hPSCs) in a single step. With the addition of a specific combination of factors, hPSCs turn into mature and functional GNs in a mere six – eight weeks. This is about two – three times faster than the 10 - 30 weeks required for previous protocols. In addition, this new protocol is highly efficient, with GNs making up more than 80 per cent of the final neuron population.

To develop this protocol, the team from Duke-NUS Medical School (Duke-NUS), A*STAR’s Genome Institute of Singapore (GIS) and the National Neuroscience Institute (NNI) first identified genetic factors involved in GN development in the brain. The team then tried many different combinations of these factors, and succeeded in confirming that mature and functional human GNs were indeed generated.

“Just like how a balance of Yin and Yang is needed in order to stay healthy, a balance of ENs and GNs is required for normal brain function. We now know a fair bit about ENs because we have good protocols to make them. However, we still know very little of the other player, the GNs, because current protocols do not work well. Yet, when these GNs malfunction our brain goes haywire,” commented Dr Alfred Sun, a Research Fellow at NNI and co-first author of the publication alongside Mr Qiang Yuan, an NUS Graduate School PhD student.

“Our quick, efficient and easy way to mass produce GNs for lab use is a game changer for neuroscience and drug discovery. With increased recognition of the essential role of GNs in almost all neurological and psychiatric diseases, we envisage our new method to be widely used to advance research and drug screening,” said Dr Shawn Je, Assistant Professor in the Neuroscience and Behavioural Disorders Programme at Duke-NUS, and senior author of the study.

The speed and efficiency of generating GNs with this new protocol provides researchers unprecedented access to the quantities of neurons necessary for studying the role of GNs in disease mechanisms. Drugs and small molecules may now be screened at an unparalleled rate to discover the next blockbuster treatment for autism, schizophrenia, and epilepsy.