Staff Pick Of The Week

Superfluid Helium

It was previously thought that superfluid Helium would flow continuously without losing kinetic energy. Mathematicians at Newcastle University demonstrated that this is only the case on a surface completely smooth down to the scale of nanometers; and no surface is that smooth.

When a regular fluid like water is passing over a surface, friction creates a boundary layer that ‘sticks’ to surfaces. Just like a regular fluid, when superfluid Helium passes over a rough surface there is a boundary layer created. However the cause is very different. As superfluid Helium flows past a rough surface, mini tornados are created which tangle up and stick together creating a slow-moving boundary layer between the free-moving fluid and the surface. This lack of viscosity is one of the key features that define what a superfluid is and now we know why it still loses kinetic energy when passing over a rough surface.

Now we can use this information to help our efforts on applications of superfluids in precision measurement devices such as gyroscopes (I think this was on the Big Bang theory where they make a gyroscope using superfluid Helium that can maintain angular momentum indefinitely because it would flow across a smooth surface without losing kinetic energy) and as coolants.

Entanglement Made Simple, a divulgative article of theoretical physicist and Nobel laureate Frank Wilczek, in Quanta Magazine.

Image by James O'Brien for Quanta Magazine

Artist profile: Gerard Sekoto

‘Art is the spark, the illumination which is socially significant for it brings about understanding’ – Gerard Sekoto (1913–1993)

Gerard Sekoto was born in Botshabelo, Mpumalanga province, in 1913, the year in which the Natives Land Act dispossessed many black South Africans of their ancestral lands. In 1938 Sekoto moved to Sophiatown, Johannesburg. He held his first solo exhibition the following year, and in 1940 the Johannesburg Art Gallery purchased his work Yellow Houses – A Street in Sophiatown (1939–1940). It was the first painting by a black South African artist to be acquired by a South African art institution, although Sekoto had to pose as a cleaner to see his own painting hanging in the gallery.

Sekoto based this painting, titled Song of the Pick (1946), on a photograph taken in the 1930s of black South African workers labouring under the watchful eye of a white foreman standing behind them. However, in his painting the dynamic has changed. Sekoto has enhanced the grace and power of the labourers, turning them to confront the small and puny figure of the overseer, who appears about to be impaled by their pickaxes.

Sekoto painted this work in the township of Eastwood in Pretoria, shortly before moving to Paris in what became a lifelong exile from South Africa. During the 1980s, postcard-sized reproductions of this iconic painting were widely distributed in South Africa, as both a badge of honour and a source of inspiration in the struggle against apartheid.

Explore a diverse range of art stretching back 100,000 years in our exhibition South Africa: the art of a nation (27 October 2016 – 26 February 2017).

Exhibition sponsored by Betsy and Jack Ryan

Logistics partner IAG Cargo

Song of the Pick, 1946. Image © Iziko Museums of South Africa, Art Collections, Cape Town. Photo by Carina Beyer.

Song of the Pick was based on this image, taken by photographer Andrew Goldie in the 1930s.

In a recent video, Practical Engineering tackles an important and often-overlooked challenge in civil engineering: dam failure. At its simplest, a levee or dam is a wall built to hold back water, and the higher that water is, the greater the pressure at its base. That pressure can drive water to seep between the grains of soil beneath the dam. As you can see in the demo below, seeping water can take a curving path through the soil beneath a dam in order to get to the other side. When too much water makes it into the soil, it pushes grains apart and makes them slip easily; this is known as liquefaction. As the name suggests, the sediment begins behaving like a fluid, quickly leading to a complete failure of the dam as its foundation flows away. With older infrastructure and increased flooding from extreme weather events, this is a serious problem facing many communities. (Video and image credit: Practical Engineering)

The Christopher Robin Story Book from When we were very young, Now we are six, Winnie the Pooh, The House at Pooh Corner by AA Milne Illustrated by Ernest H Shepard London Methuen & Co Ltd. First Edition 1929

David in Singapore, Serious Moonlight Tour 1983

Photo © Denis O’Regan

CHAUVET CAVE: 

THE  Chauvet Cave (also known as the Chauvet-Pont-d’Arc Cave) is a Palaeolithic cave situated near Vallon-Pont-d’Arc in the Ardèche region of southern France that houses impeccably preserved, exquisite examples of prehistoric art. 

Now reliably dated to between c. 33,000 and c. 30,000 years ago, the numerous and diverse animals that dot the interior walls of the cave – both painted and engraved – show such high artistic quality that they were initially thought to have been closer in age to the similarly stunning, but much younger art in caves such as the Lascaux Cave. Its age and artistry have made us reconsider the story of art as well as the capabilities of these humans. The cave has been granted UNESCO World Heritage status.

Read More 

Article by Emma Groeneveld on AHE

Farming amoebae carry around detoxifying food

Five years ago, the Queller-Strassmann lab at Rice University, now at Washington University in St. Louis, demonstrated that the social amoeba Dictyostelium discoideum – affectionately nicknamed “Dicty” – can maintain a crop of food bacteria from generation to generation, giving these farmers an advantage when food is scarce.

Now, new research from the same team shows that these microscopic farmers also rely on their symbiotic bacteria to protect themselves from environmental toxins, a little-studied but increasingly clear role microbes can play for their hosts.

Research scientist Debra Brock led the new work, published April 20 in the Proceedings of the Royal Society B.

These amoebae are content to be loners when food is abundant, but when it’s depleted they come together in the tens of thousands to cooperate. They transform into a mobile slug that migrates in search of fairer conditions and then produces hardy spores to release into the environment and wait out the lean times.

The slug has a tiny pool of specialized cells, called sentinels, that protect it from pests and poisons by ferrying them away.

“The sentinel cells pass through the body, mopping up toxins, bacteria, and essentially serving as a liver, a kidney, and innate immune system and being left behind in the slime trail,” said Joan Strassmann, PhD, the Charles Rebstock Professor of Biology in Arts & Sciences.

Debra A. Brock, W. Éamon Callison, Joan E. Strassmann, David C. Queller. Sentinel cells, symbiotic bacteria and toxin resistance in the social amoebaDictyostelium discoideum. Proceedings of the Royal Society B: Biological Sciences, 2016; 283 (1829): 20152727 DOI: 10.1098/rspb.2015.2727

The social amoeba Dictyostelium discoideum has both solitary and communal life stages. As long as food is abundant, it lives on its own, but when food is scarce the amoebae seek one another out. Together they form a slug that migrates toward the light and then a fruiting body that disperses spores from atop a stalk. The fruiting bodies are pictured here. Credit: Strassmann/Queller lab

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