John Sebastian
@johnseb.bsky.social
Fluid Mechanics, etc
https://john-seb.github.io/
https://john-seb.github.io/
Pinned
John Sebastian
@johnseb.bsky.social
· Mar 9
Our new paper is now out in PNAS: "The geometry of Nature’s stingers is universal due to stochastic mechanical wear." doi.org/10.1073/pnas... . Original artwork by John Sebastian
On ’pointless’ optima in Nature!
Out now in @pnas.org
From #DTU #DK
Thanks @villumfonden.bsky.social
🧪 ⚛️
Out now in @pnas.org
From #DTU #DK
Thanks @villumfonden.bsky.social
🧪 ⚛️
Reposted by John Sebastian
🔬 At the 13th #CMiF #SummerSchool, Cheikh, Gauri and Lorena presented their research on the #Leidenfrost effect and, more importantly, put their results in front of researchers outside the project.
One of the most useful exercises in a PhD.
#LeidenForce #DTU
One of the most useful exercises in a PhD.
#LeidenForce #DTU
August 24, 2026 at 12:21 PM
🔬 At the 13th #CMiF #SummerSchool, Cheikh, Gauri and Lorena presented their research on the #Leidenfrost effect and, more importantly, put their results in front of researchers outside the project.
One of the most useful exercises in a PhD.
#LeidenForce #DTU
One of the most useful exercises in a PhD.
#LeidenForce #DTU
Reposted by John Sebastian
Including this mass asymmetry in the reduced order model produces a system which is related to the 4D Lorenz system, or the Malkus-Robbins system. Because so much is known about the Lorenz system, these connections allow us to predict behavior transition (bifurcation) times, and more. (7/10)
August 21, 2026 at 2:00 PM
Including this mass asymmetry in the reduced order model produces a system which is related to the 4D Lorenz system, or the Malkus-Robbins system. Because so much is known about the Lorenz system, these connections allow us to predict behavior transition (bifurcation) times, and more. (7/10)
Reposted by John Sebastian
Why do primary plant tissues hold their shape? We are told it's because of turgor pressure—but how does that work mechanically?
We investigated how pressurized cylindrical structures support themselves.
Read here:
doi.org/10.1039/d6sm...
Funded by @hfspo.bsky.social
www.plantbiomechanics.net
We investigated how pressurized cylindrical structures support themselves.
Read here:
doi.org/10.1039/d6sm...
Funded by @hfspo.bsky.social
www.plantbiomechanics.net
July 19, 2026 at 4:41 PM
Why do primary plant tissues hold their shape? We are told it's because of turgor pressure—but how does that work mechanically?
We investigated how pressurized cylindrical structures support themselves.
Read here:
doi.org/10.1039/d6sm...
Funded by @hfspo.bsky.social
www.plantbiomechanics.net
We investigated how pressurized cylindrical structures support themselves.
Read here:
doi.org/10.1039/d6sm...
Funded by @hfspo.bsky.social
www.plantbiomechanics.net
Reposted by John Sebastian
A reverse sprinkler draws in fluid rather than ejecting it. The geometry of the reverse sprinkler’s arms drives its rotation: specifically, the flux in the angular momentum of the fluid being injected into the central hub of the sprinkler. In PNAS: https://ow.ly/K1C650Zoa3H
July 18, 2026 at 2:00 AM
A reverse sprinkler draws in fluid rather than ejecting it. The geometry of the reverse sprinkler’s arms drives its rotation: specifically, the flux in the angular momentum of the fluid being injected into the central hub of the sprinkler. In PNAS: https://ow.ly/K1C650Zoa3H
Reposted by John Sebastian
🎨🔬 Can techniques from the arts become tools for scientific discovery?
Our new preprint introduces glass-based physical models for studying tissue mechanics, bridging art, physics, engineering, and biology! 😀
📄 arxiv.org/abs/2606.22281
Our new preprint introduces glass-based physical models for studying tissue mechanics, bridging art, physics, engineering, and biology! 😀
📄 arxiv.org/abs/2606.22281
June 23, 2026 at 5:40 PM
🎨🔬 Can techniques from the arts become tools for scientific discovery?
Our new preprint introduces glass-based physical models for studying tissue mechanics, bridging art, physics, engineering, and biology! 😀
📄 arxiv.org/abs/2606.22281
Our new preprint introduces glass-based physical models for studying tissue mechanics, bridging art, physics, engineering, and biology! 😀
📄 arxiv.org/abs/2606.22281
Reposted by John Sebastian
The molecular origin of this rapid softening remains unknown. Future studies and new genetic tools are needed to uncover the signals driving the ultra-fast mechanical remodeling of the cell wall.
Full paper in @science.org:
www.science.org/doi/10.1126/...
Full paper in @science.org:
www.science.org/doi/10.1126/...
Fast cell wall softening causes Venus flytrap closure
Plants can move rapidly without muscles, as seen in the Venus flytrap’s snapping lobes—a long-standing puzzle in plant biomechanics. Trap closure involves an elastic instability, but the active mechan...
www.science.org
June 13, 2026 at 2:19 PM
The molecular origin of this rapid softening remains unknown. Future studies and new genetic tools are needed to uncover the signals driving the ultra-fast mechanical remodeling of the cell wall.
Full paper in @science.org:
www.science.org/doi/10.1126/...
Full paper in @science.org:
www.science.org/doi/10.1126/...
Reposted by John Sebastian
I am looking for a Post-doc in Oxford to work with me on morphogenesis at the cellular scale, with particular emphasis on growth processes and their mechanical and dynamical consequences.
Please circulate
my.corehr.com/pls/uoxrecru...
This bristle is created by a single cell! Let's model it.
Please circulate
my.corehr.com/pls/uoxrecru...
This bristle is created by a single cell! Let's model it.
May 15, 2026 at 1:13 PM
I am looking for a Post-doc in Oxford to work with me on morphogenesis at the cellular scale, with particular emphasis on growth processes and their mechanical and dynamical consequences.
Please circulate
my.corehr.com/pls/uoxrecru...
This bristle is created by a single cell! Let's model it.
Please circulate
my.corehr.com/pls/uoxrecru...
This bristle is created by a single cell! Let's model it.
I’ve now heard from the 10th person who appreciated the nerd callout in the footnote!
Spikes are a lie. They are not as spiky as they might appear.
Across nature, spikes end in a blunt, paraboloid curve — the universal curve of stabbiness.
And that's true at EVERY SCALE. From microscopic to narwhal.
Why? Whence cometh the universal stabby curve?
Science has your answers: 🧪
Across nature, spikes end in a blunt, paraboloid curve — the universal curve of stabbiness.
And that's true at EVERY SCALE. From microscopic to narwhal.
Why? Whence cometh the universal stabby curve?
Science has your answers: 🧪
Stingers and spikes across nature have the same shape. Here's why.
Not everything in biology evolved for a purpose.
www.reviewertoo.com
April 12, 2026 at 2:34 PM
I’ve now heard from the 10th person who appreciated the nerd callout in the footnote!
Reposted by John Sebastian
Preprint 🌱 Plants build nonlinear vectorial representations of light patterns!
Surprising results: Opposing cues cancel, so plants grow towards a weaker tie-breaker light.
Plants respond to sum of transduced signals, not physical sum of light: optical “illusions”! 🪩
tinyurl.com/44f83xh8
Surprising results: Opposing cues cancel, so plants grow towards a weaker tie-breaker light.
Plants respond to sum of transduced signals, not physical sum of light: optical “illusions”! 🪩
tinyurl.com/44f83xh8
April 3, 2026 at 1:54 PM
Preprint 🌱 Plants build nonlinear vectorial representations of light patterns!
Surprising results: Opposing cues cancel, so plants grow towards a weaker tie-breaker light.
Plants respond to sum of transduced signals, not physical sum of light: optical “illusions”! 🪩
tinyurl.com/44f83xh8
Surprising results: Opposing cues cancel, so plants grow towards a weaker tie-breaker light.
Plants respond to sum of transduced signals, not physical sum of light: optical “illusions”! 🪩
tinyurl.com/44f83xh8
Reposted by John Sebastian
🌱 “To twine or not to twine?”
Preprint 🪩 Plants use inherent circular movements (circumnuations) for active sensing of support mechanical stability (eg whisking 🐭), twining occurs at a torque threshold. Heroic experiments by Amir Ohad, fancy simulations @amirporat.bsky.social:
tinyurl.com/2syh4ny3
Preprint 🪩 Plants use inherent circular movements (circumnuations) for active sensing of support mechanical stability (eg whisking 🐭), twining occurs at a torque threshold. Heroic experiments by Amir Ohad, fancy simulations @amirporat.bsky.social:
tinyurl.com/2syh4ny3
March 30, 2026 at 7:33 AM
🌱 “To twine or not to twine?”
Preprint 🪩 Plants use inherent circular movements (circumnuations) for active sensing of support mechanical stability (eg whisking 🐭), twining occurs at a torque threshold. Heroic experiments by Amir Ohad, fancy simulations @amirporat.bsky.social:
tinyurl.com/2syh4ny3
Preprint 🪩 Plants use inherent circular movements (circumnuations) for active sensing of support mechanical stability (eg whisking 🐭), twining occurs at a torque threshold. Heroic experiments by Amir Ohad, fancy simulations @amirporat.bsky.social:
tinyurl.com/2syh4ny3
Reposted by John Sebastian
Capitalizing on a mechanoelectrical mechanism that arises from the spines’ structure could yield useful sensors for marine environmental monitoring and other applications. #physics #biophysics
Sea urchin species discerns surroundings with electrically responsive spines
Capitalizing on a mechanoelectrical mechanism that arises from the spines’ structure could yield useful sensors for marine environmental monitoring and other applications.
physicstoday.aip.org
March 20, 2026 at 6:43 PM
Capitalizing on a mechanoelectrical mechanism that arises from the spines’ structure could yield useful sensors for marine environmental monitoring and other applications. #physics #biophysics
"Nothing happens to anyone that he is not fitted by nature to bear" - Maximus
🧪⚛️🎢🧮
🧪⚛️🎢🧮
Pencil gladiators? Elise Cutts has the story
www.reviewertoo.com/stingers-and...
www.reviewertoo.com/stingers-and...
March 13, 2026 at 10:11 AM
"Nothing happens to anyone that he is not fitted by nature to bear" - Maximus
🧪⚛️🎢🧮
🧪⚛️🎢🧮
✐ᝰ ✏️
🧪⚛️🎢🧮
🧪⚛️🎢🧮
Medium: graphite, clay, and wood
Period: Late-stage procrastination
jensen-lab.github.io/Universal_Sh...
Period: Late-stage procrastination
jensen-lab.github.io/Universal_Sh...
March 12, 2026 at 2:22 PM
✐ᝰ ✏️
🧪⚛️🎢🧮
🧪⚛️🎢🧮
Reposted by John Sebastian
Comics by Caroline Hu here
March 11, 2026 at 6:53 PM
Comics by Caroline Hu here
Reposted by John Sebastian
I decided to highlight this study for two reasons:
1) It is fun. There's an experiment involving "pencil gladiators." And spikes across scale. Need I say more.
2) It's a good reminder that not everything in biology exists to serve some evolutionary purpose. Biology is also physics.
1) It is fun. There's an experiment involving "pencil gladiators." And spikes across scale. Need I say more.
2) It's a good reminder that not everything in biology exists to serve some evolutionary purpose. Biology is also physics.
March 10, 2026 at 3:39 PM
I decided to highlight this study for two reasons:
1) It is fun. There's an experiment involving "pencil gladiators." And spikes across scale. Need I say more.
2) It's a good reminder that not everything in biology exists to serve some evolutionary purpose. Biology is also physics.
1) It is fun. There's an experiment involving "pencil gladiators." And spikes across scale. Need I say more.
2) It's a good reminder that not everything in biology exists to serve some evolutionary purpose. Biology is also physics.
Reposted by John Sebastian
To make a long story short: the universal stabby curve cometh from mechanical weathering.
It is not some evolved optimum solution for stabbing, it is just the shape you get if you expose a pointy thing to the elements for long enough.
It is not some evolved optimum solution for stabbing, it is just the shape you get if you expose a pointy thing to the elements for long enough.
March 10, 2026 at 3:39 PM
To make a long story short: the universal stabby curve cometh from mechanical weathering.
It is not some evolved optimum solution for stabbing, it is just the shape you get if you expose a pointy thing to the elements for long enough.
It is not some evolved optimum solution for stabbing, it is just the shape you get if you expose a pointy thing to the elements for long enough.
Reposted by John Sebastian
Spikes are a lie. They are not as spiky as they might appear.
Across nature, spikes end in a blunt, paraboloid curve — the universal curve of stabbiness.
And that's true at EVERY SCALE. From microscopic to narwhal.
Why? Whence cometh the universal stabby curve?
Science has your answers: 🧪
Across nature, spikes end in a blunt, paraboloid curve — the universal curve of stabbiness.
And that's true at EVERY SCALE. From microscopic to narwhal.
Why? Whence cometh the universal stabby curve?
Science has your answers: 🧪
Stingers and spikes across nature have the same shape. Here's why.
Not everything in biology evolved for a purpose.
www.reviewertoo.com
March 10, 2026 at 3:39 PM
Spikes are a lie. They are not as spiky as they might appear.
Across nature, spikes end in a blunt, paraboloid curve — the universal curve of stabbiness.
And that's true at EVERY SCALE. From microscopic to narwhal.
Why? Whence cometh the universal stabby curve?
Science has your answers: 🧪
Across nature, spikes end in a blunt, paraboloid curve — the universal curve of stabbiness.
And that's true at EVERY SCALE. From microscopic to narwhal.
Why? Whence cometh the universal stabby curve?
Science has your answers: 🧪
Reposted by John Sebastian
Very cool! It always amazes me how different problems can look very similar once put into equations. The sublimation of sharp tips also yields a curvature decreasing as t^(-1/2) because the receding velocity scales with the curvature locally (doi.org/10.1038/s414...).
March 9, 2026 at 4:01 PM
Very cool! It always amazes me how different problems can look very similar once put into equations. The sublimation of sharp tips also yields a curvature decreasing as t^(-1/2) because the receding velocity scales with the curvature locally (doi.org/10.1038/s414...).
Reposted by John Sebastian
Our new paper is now out in PNAS: "The geometry of Nature’s stingers is universal due to stochastic mechanical wear." doi.org/10.1073/pnas... . Original artwork by John Sebastian
March 9, 2026 at 11:55 AM
Our new paper is now out in PNAS: "The geometry of Nature’s stingers is universal due to stochastic mechanical wear." doi.org/10.1073/pnas... . Original artwork by John Sebastian
On ’pointless’ optima in Nature!
Out now in @pnas.org
From #DTU #DK
Thanks @villumfonden.bsky.social
🧪 ⚛️
Out now in @pnas.org
From #DTU #DK
Thanks @villumfonden.bsky.social
🧪 ⚛️
Our new paper is now out in PNAS: "The geometry of Nature’s stingers is universal due to stochastic mechanical wear." doi.org/10.1073/pnas... . Original artwork by John Sebastian
March 9, 2026 at 1:50 PM
On ’pointless’ optima in Nature!
Out now in @pnas.org
From #DTU #DK
Thanks @villumfonden.bsky.social
🧪 ⚛️
Out now in @pnas.org
From #DTU #DK
Thanks @villumfonden.bsky.social
🧪 ⚛️
Reposted by John Sebastian
🎮 pokemon tree of life
for pokémon's 30th anniversary, explore a visualization and field guide to 1,000+ pokémon. what inspired them, where they came from, and how they connect.
포켓몬 30주년, 1,000개 이상의 포켓몬을 시각화했습니다!
➡️ str.sg/viz-poke30
for pokémon's 30th anniversary, explore a visualization and field guide to 1,000+ pokémon. what inspired them, where they came from, and how they connect.
포켓몬 30주년, 1,000개 이상의 포켓몬을 시각화했습니다!
➡️ str.sg/viz-poke30
February 27, 2026 at 5:18 AM
🎮 pokemon tree of life
for pokémon's 30th anniversary, explore a visualization and field guide to 1,000+ pokémon. what inspired them, where they came from, and how they connect.
포켓몬 30주년, 1,000개 이상의 포켓몬을 시각화했습니다!
➡️ str.sg/viz-poke30
for pokémon's 30th anniversary, explore a visualization and field guide to 1,000+ pokémon. what inspired them, where they came from, and how they connect.
포켓몬 30주년, 1,000개 이상의 포켓몬을 시각화했습니다!
➡️ str.sg/viz-poke30
Reposted by John Sebastian
It took me quite some time, but the article following a talk at the DFD 2024 is finally online! Clogging is widespread, but the associated physics remains poorly understood. I am trying to give a (biased) view and some general knowledge here: doi.org/10.1103/rfk8...
February 23, 2026 at 11:35 PM
It took me quite some time, but the article following a talk at the DFD 2024 is finally online! Clogging is widespread, but the associated physics remains poorly understood. I am trying to give a (biased) view and some general knowledge here: doi.org/10.1103/rfk8...
Reposted by John Sebastian
Our new paper, led by @ramsudhirsharma.bsky.social (with Alexandre Leonelli, Kevin Zhao, Eckart Meiburg), has been published in @apsphysics.bsky.social PRL. We revisit hourglasses/silos and ask what really sets the discharge rate. See more here: doi.org/10.1103/3g2f-nslz
February 18, 2026 at 2:48 AM
Our new paper, led by @ramsudhirsharma.bsky.social (with Alexandre Leonelli, Kevin Zhao, Eckart Meiburg), has been published in @apsphysics.bsky.social PRL. We revisit hourglasses/silos and ask what really sets the discharge rate. See more here: doi.org/10.1103/3g2f-nslz
🧪⚛️
This week, I tried to recreate the cover image of Benny Lautrup’s Physics of Continuous Matter, using nothing more exotic than syrup and glitter. #FluidsFriday
January 30, 2026 at 7:39 PM
🧪⚛️
Reposted by John Sebastian
We’ve been putting together a small device to study flow through pores, where geometry matters and minor imperfections can make or break the experiment. The goal is simple to state and nontrivial to execute. One early prototype looks, quite unintentionally, like a Picasso: a face, a pair of eyes.
January 23, 2026 at 12:13 PM
We’ve been putting together a small device to study flow through pores, where geometry matters and minor imperfections can make or break the experiment. The goal is simple to state and nontrivial to execute. One early prototype looks, quite unintentionally, like a Picasso: a face, a pair of eyes.