Fluid Flows Break Up Microswimmer Clumps

The field of active matter looks at the collective motion of particles and organisms–how birds flock and fish school. In systems of “dry” squirmers–those that have no hydrodynamic interactions with one another–clumps of squirmers can form with empty spaces in between them. This is known as motility-induced phase separation, or MIPS. Researchers wondered whether microswimmers in a fluid–which do produce hydrodynamic forces that can affect one another–would also show MIPS.

In a new study, researchers show, instead, that hydrodynamic interactions between swimmers will prevent (or destroy) these clumps. Through a combination of theoretical work and simulation, the authors found that translational flows between swimmers swept the swimmers out of clumps as they formed. Rotational flows between swimmers made them able to change direction faster, which also kept stable clumps from forming. (Image and research credit: T. Zhou and J. Brady; via APS)

Ever noticed patterns in your tea or coffee? Share your swirls and see if Marvin approves.

Marvin measures the swirl

Marvin tried measuring the curvature of cream in his tea…
Conclusions were inconclusive, but delightfully swirly.
Half here, half there, Marvin studies boundaries, one sip at a time.
Observing patterns is tricky when you’re partly in another universe, but curiosity never rests. 🫖

Hashtags:
#MarvinCuriosity #HybridMind42 #ScienceArt #QuantumHumour #PhaseSeparation

Meet Marvin: Schrödinger’s Cheshire, Half Here, Half There Cat

Half alive, half dead, entirely curious — Marvin explores the boundaries of reality, one sip of tea at a time.

Marvin has nine lives… or perhaps 18, or maybe even infinite today, since he’s half here, half in another universe, caught in the act of slipping through boundaries. His live cat’s eye studies the swirls of cream in his tea, while his dead eye sparkles and spirals with the playful mischief of being both exactly dead and alive, just as Schrödinger predicted.

Driven by curiosity — and fully aware that curiosity could be lethal if you’re a cat — he probes the boundaries of two phases, straddling realities with impeccable style and a sip of tea. Question-mark tail curling, he explores, observes, and survives… mostly. 🫖🖤

Hashtags:
#MarvinCuriosity #HybridMind42 #QuantumHumour #PhaseSeparation

Switchable RNA motifs for dynamic transcriptional control of RNA condensates.

#PhaseSeparation #BiomolecularCondensates #Nanostars #RNAbiology

https://academic.oup.com/nar/article/53/12/gkaf497/8169774

Cooking Perfect Cacio e Pepe

In cooking, sometimes the simplest recipes are the toughest to master. Cacio e pepe — a classic three-ingredient Italian pasta — is an excellent example. Made properly, the sauce of cheese and black pepper combines with starchy water to coat the pasta in a uniform, cheesy sauce. Or, if you’re me, you wind up with a pasta sauce flecked with stringy clumps of melted cheese. Fortunately for those of us who have yet to master this one, a new research paper has us covered with tips to make the perfect cacio e pepe.

The key to that elusive silky sauce, they found, is the starch – water – cheese combination. Your water needs just the right amount of starch — they found that between 1 – 4% starch by (cheese) mass worked. If the starch concentration is too low (which can easily happen in pasta water), you’ll get the clumpy cheese mess that so frequently happens in my kitchen. Temperature is also critical; if the water is too hot when it’s added, then it can destabilize the sauce. Check out the pre-print’s Section V for the scientific, supposedly foolproof, recipe. I know I’ll be trying it! (Image credit: O. Kadaksoo; research credit: G. Bartolucci et al. pre-print; via APS News)

#cooking #emulsion #fluidDynamics #phaseSeparation #physics #rheology #science #softMatter

Why Icy Giants Have Strange Magnetic Fields

When Voyager 2 visited Uranus and Neptune, scientists were puzzled by the icy giants’ disorderly magnetic fields. Contrary to expectations, neither planet had a well-defined north and south magnetic pole, indicating that the planets’ thick, icy interiors must not convect the way Earth’s mantle does. Years later, other researchers suggested that the icy giants’ magnetic fields could come from a single thin, convecting layer in the planet, but how that would look remained unclear. Now a scientist thinks he has an answer.

When simulating a mixture of water, methane, and ammonia under icy giant temperature and pressure conditions, he saw the chemicals split themselves into two layers — a water-hydrogen mix capable of convection and a hydrocarbon-rich, stagnant lower layer. Such phase separation, he argues, matches both the icy giants’ gravitational fields and their odd magnetic fields. To test whether the model holds up, we’ll need another spacecraft — one equipped with a Doppler imager — to visit Uranus and/or Neptune to measure the predicted layers firsthand. (Image credit: NASA; research credit: B. Militzer; via Physics World)

#convection #fluidDynamics #Neptune #numericalSimulation #phaseSeparation #physics #planetaryScience #science #Uranus