Pierre Haas
@lepuslapis.bsky.social
Research group leader at @mpipks.bsky.social and @mpi-cbg.de. Mechanics, mathematics, and more.
After three intense fun days of #CellPhysics2025 @uni-saarland.de, it was time to walk up a steep hill.
October 9, 2025 at 4:02 PM
After three intense fun days of #CellPhysics2025 @uni-saarland.de, it was time to walk up a steep hill.
#CellPhysics2025 @uni-saarland.de: looking forward to talking about "Mechanics of Lumina" (*) in the "Cell Collectives" session this morning.
(*) Note the use of the correct plural of "lumen".
(*) Note the use of the correct plural of "lumen".
October 8, 2025 at 6:35 AM
#CellPhysics2025 @uni-saarland.de: looking forward to talking about "Mechanics of Lumina" (*) in the "Cell Collectives" session this morning.
(*) Note the use of the correct plural of "lumen".
(*) Note the use of the correct plural of "lumen".
On my way to give a seminar @emergencediep.bsky.social, Amsterdam. Looking forward to the visit!
October 1, 2025 at 9:33 AM
On my way to give a seminar @emergencediep.bsky.social, Amsterdam. Looking forward to the visit!
#proudPI moment: my first #PhD student, Maryam Setoudeh, has just submitted her thesis @tudresden.bsky.social.
September 30, 2025 at 9:14 AM
#proudPI moment: my first #PhD student, Maryam Setoudeh, has just submitted her thesis @tudresden.bsky.social.
We also discover an emergent contribution of an inhomogeneous cable to the dynamics of gap closure. Our work thus explains the mechanical roles of tissue fluidisation and cable inhomogeneities in Tribolium serosa closure and processes of epiboly and wound healing more generally.
September 8, 2025 at 7:51 AM
We also discover an emergent contribution of an inhomogeneous cable to the dynamics of gap closure. Our work thus explains the mechanical roles of tissue fluidisation and cable inhomogeneities in Tribolium serosa closure and processes of epiboly and wound healing more generally.
Strikingly, very different macroscopic intercalation dynamics arise in the obvious limits: in a fluidised tissue, cells deintercalate from the gap edge into the tissue bulk, while they intercalate into the gap if the energy barrier to intercalations is high.
September 8, 2025 at 7:51 AM
Strikingly, very different macroscopic intercalation dynamics arise in the obvious limits: in a fluidised tissue, cells deintercalate from the gap edge into the tissue bulk, while they intercalate into the gap if the energy barrier to intercalations is high.
We combine an elastic sheet theory for the tissue with a coarse-grained model of the intercalations to show how the macroscopic dynamics of gap closure depend on the microscopic details of the energy barrier to intercalations.
September 8, 2025 at 7:51 AM
We combine an elastic sheet theory for the tissue with a coarse-grained model of the intercalations to show how the macroscopic dynamics of gap closure depend on the microscopic details of the energy barrier to intercalations.
Epithelial gap closure is a key tissue movement during #development, needing cell rearrangements at the gap edge. To understand the interplay of these plastic cell intercalations with the tissue elasticity, we study a minimal model of a circular gap bounded by a contractile cable in a flat tissue.
September 8, 2025 at 7:51 AM
Epithelial gap closure is a key tissue movement during #development, needing cell rearrangements at the gap edge. To understand the interplay of these plastic cell intercalations with the tissue elasticity, we study a minimal model of a circular gap bounded by a contractile cable in a flat tissue.
Another #preprint: "Elasticity and plasticity of epithelial gap closure", from the #PhD work of Maryam Setoudeh:
arxiv.org/abs/2509.05110
This one required a lot of (I think) beautiful #mechanics!
@mpipks.bsky.social @mpi-cbg.de @csbdresden.bsky.social
arxiv.org/abs/2509.05110
This one required a lot of (I think) beautiful #mechanics!
@mpipks.bsky.social @mpi-cbg.de @csbdresden.bsky.social
September 8, 2025 at 7:51 AM
Another #preprint: "Elasticity and plasticity of epithelial gap closure", from the #PhD work of Maryam Setoudeh:
arxiv.org/abs/2509.05110
This one required a lot of (I think) beautiful #mechanics!
@mpipks.bsky.social @mpi-cbg.de @csbdresden.bsky.social
arxiv.org/abs/2509.05110
This one required a lot of (I think) beautiful #mechanics!
@mpipks.bsky.social @mpi-cbg.de @csbdresden.bsky.social
The model makes a couple of additional testable (and tested!) predictions. Our work thus shows how regulation of the mechanics of all cell surfaces conspires to control lumen morphology.
September 5, 2025 at 8:59 AM
The model makes a couple of additional testable (and tested!) predictions. Our work thus shows how regulation of the mechanics of all cell surfaces conspires to control lumen morphology.
The model reproduces the experimental shape instability quantitatively, explaining the observed increase of lateral contractility as a cellular response countering the instability.
September 5, 2025 at 8:59 AM
The model reproduces the experimental shape instability quantitatively, explaining the observed increase of lateral contractility as a cellular response countering the instability.
We develop a mean-field vertex model that shows how the interplay of pressure, adhesion, and cortex mechanics determines the observed (in)stability of apical surfaces.
September 5, 2025 at 8:59 AM
We develop a mean-field vertex model that shows how the interplay of pressure, adhesion, and cortex mechanics determines the observed (in)stability of apical surfaces.
We study this interplay using MDCK cysts (with tight junction perturbations). We quantify the mechanical differences between apical, basal, lateral cell surfaces experimentally.
September 5, 2025 at 8:59 AM
We study this interplay using MDCK cysts (with tight junction perturbations). We quantify the mechanical differences between apical, basal, lateral cell surfaces experimentally.
Formation of lumina (yes, that's the only acceptable plural) is inextricably linked to establishment of apicobasal polarity, yet it is unknown how the resulting mechanical differences between apical, basal, lateral cell surfaces determine lumen shape together with cell-cell adhesion, lumen pressure.
September 5, 2025 at 8:59 AM
Formation of lumina (yes, that's the only acceptable plural) is inextricably linked to establishment of apicobasal polarity, yet it is unknown how the resulting mechanical differences between apical, basal, lateral cell surfaces determine lumen shape together with cell-cell adhesion, lumen pressure.
New #preprint: "Control of lumen morphology by lateral and basal cell surfaces", a great #biophysics collaboration with Chandraniva Guha Ray, @markusmukenhirn.bsky.social, Alf Honigmann @biotec-tud.bsky.social @poldresden.bsky.social.
arxiv.org/abs/2509.04316
@mpipks.bsky.social @mpi-cbg.de
arxiv.org/abs/2509.04316
@mpipks.bsky.social @mpi-cbg.de
September 5, 2025 at 8:59 AM
New #preprint: "Control of lumen morphology by lateral and basal cell surfaces", a great #biophysics collaboration with Chandraniva Guha Ray, @markusmukenhirn.bsky.social, Alf Honigmann @biotec-tud.bsky.social @poldresden.bsky.social.
arxiv.org/abs/2509.04316
@mpipks.bsky.social @mpi-cbg.de
arxiv.org/abs/2509.04316
@mpipks.bsky.social @mpi-cbg.de
We use our approach to prove that certain networks interactions of N=4 species are "impossible ecologies" in which coexistence is nontrivially impossible, and discover a combinatorial obstruction to coexistence in "symmetric" interaction networks.
September 3, 2025 at 8:15 AM
We use our approach to prove that certain networks interactions of N=4 species are "impossible ecologies" in which coexistence is nontrivially impossible, and discover a combinatorial obstruction to coexistence in "symmetric" interaction networks.
We introduce ideas from (numerical) algebraic geometry into theoretical ecology by studying steady-state coexistence in the Lotka–Volterra equations, encoding the feasibility and (Routh–Hurwitz) stability conditions on the Grassmannian and using the power of the Plücker embedding.
September 3, 2025 at 8:15 AM
We introduce ideas from (numerical) algebraic geometry into theoretical ecology by studying steady-state coexistence in the Lotka–Volterra equations, encoding the feasibility and (Routh–Hurwitz) stability conditions on the Grassmannian and using the power of the Plücker embedding.
On our way to the @mpi-cbg.de faculty retreat with @paveltomancak.bsky.social @nadlerlab.bsky.social, Eric, Alex - using the only acceptable means of transport.
September 1, 2025 at 6:32 AM
On our way to the @mpi-cbg.de faculty retreat with @paveltomancak.bsky.social @nadlerlab.bsky.social, Eric, Alex - using the only acceptable means of transport.
On the theory side, we introduce regularised hydrodynamic singularities as minimal models for inferring inter-tissue forces in development (and find new singularities for the Brinkman equations).
July 4, 2025 at 6:07 PM
On the theory side, we introduce regularised hydrodynamic singularities as minimal models for inferring inter-tissue forces in development (and find new singularities for the Brinkman equations).
We test our mechanical mechanism not only in vivo, but also by identifying the minimal set of hydrodynamic forces necessary for reproducing the observed tissue flows even qualitatively, and by showing that this minimal set is also sufficient to reproduce these flows quantitatively.
July 4, 2025 at 6:07 PM
We test our mechanical mechanism not only in vivo, but also by identifying the minimal set of hydrodynamic forces necessary for reproducing the observed tissue flows even qualitatively, and by showing that this minimal set is also sufficient to reproduce these flows quantitatively.
Now (finally) #published @natcomms.nature.com: "A multi-tiered mechanical mechanism shapes the early neural plate" @mpipks.bsky.social @mpi-cbg.de
A great collaboration of experiment and theory to explain the tissue flows shaping the #zebrafish neural plate!
doi.org/10.1038/s41467-025-61303-1
A great collaboration of experiment and theory to explain the tissue flows shaping the #zebrafish neural plate!
doi.org/10.1038/s41467-025-61303-1
July 4, 2025 at 6:07 PM
Now (finally) #published @natcomms.nature.com: "A multi-tiered mechanical mechanism shapes the early neural plate" @mpipks.bsky.social @mpi-cbg.de
A great collaboration of experiment and theory to explain the tissue flows shaping the #zebrafish neural plate!
doi.org/10.1038/s41467-025-61303-1
A great collaboration of experiment and theory to explain the tissue flows shaping the #zebrafish neural plate!
doi.org/10.1038/s41467-025-61303-1
Sunset at Dynamics Days Europe #DDays2025 in Thessaloniki!
I talked about "Dynamics of small ecological communities" in a great mini-symposium organised by @yumeng0806.bsky.social, Bo-Wei Qin.
My talk included our recent doi.org/10.1016/j.cels.2025.101297 @cp-cellsystems.bsky.social.
I talked about "Dynamics of small ecological communities" in a great mini-symposium organised by @yumeng0806.bsky.social, Bo-Wei Qin.
My talk included our recent doi.org/10.1016/j.cels.2025.101297 @cp-cellsystems.bsky.social.
June 26, 2025 at 7:55 AM
Sunset at Dynamics Days Europe #DDays2025 in Thessaloniki!
I talked about "Dynamics of small ecological communities" in a great mini-symposium organised by @yumeng0806.bsky.social, Bo-Wei Qin.
My talk included our recent doi.org/10.1016/j.cels.2025.101297 @cp-cellsystems.bsky.social.
I talked about "Dynamics of small ecological communities" in a great mini-symposium organised by @yumeng0806.bsky.social, Bo-Wei Qin.
My talk included our recent doi.org/10.1016/j.cels.2025.101297 @cp-cellsystems.bsky.social.
In the process, we prove a nice theorem about extensions of ecological communities and discover curious "impossible" and "irreducible" ecological networks.
June 17, 2025 at 11:50 AM
In the process, we prove a nice theorem about extensions of ecological communities and discover curious "impossible" and "irreducible" ecological networks.
We analyse all interaction networks of competitive, mutualistic, and predator-prey interactions of N < 6 species to show how the probability of stable and feasible coexistence depends hugely on details of the interaction network structure that cannot be captured fully by random-matrix theory.
June 17, 2025 at 11:50 AM
We analyse all interaction networks of competitive, mutualistic, and predator-prey interactions of N < 6 species to show how the probability of stable and feasible coexistence depends hugely on details of the interaction network structure that cannot be captured fully by random-matrix theory.