Modeling, slicing, rapid prototyping:
\r\nLearn to see your mechanical projects through to completion.
This talk is meant to give an overview of the semantics of HoTT in (∞,1)-categories, tackling the key challenge of rigidification: the process of bridging homotopy-coherent notions phrased in models of higher categories such as quasicategories, and their type-theoretical counterparts that must account for the inherent strictness of type theory.
\r\nAfter quickly recalling the usual categorical semantics of extensional Martin-Löf type theory within locally cartesian closed category, the plan is to present some useful ideas to carry over some of the argument to the higher setting. Specifically, I will discuss the process of turning an elementary higher topos into a model of HoTT, and sketch important ideas used to prove the internal language conjecture for locally cartesian closed (∞,1)-categories.
\r\n
\r\n
In migrating cells, the GTPase Rac organizes a protrusive front, whereas Rho organizes a contractile back, yet how these GTPases segregate remains unclear. We leverage optogenetics, mechanical perturbations, and modeling to reveal a mechanochemical long-range mutual activation between front and back polarity programs that complements their known local mutual inhibition. Rac-driven protrusions increase membrane tension, triggering mTORC2-dependent Rho activation at the opposite side of the cell. Conversely, Rho-mediated contractility induces cortical-flow regulation of phosphoinositide signaling, promoting distal Rac activation. Our findings demonstrate how the actin cortex and plasma membrane interact as an integrated mechanochemical system for long-range Rac-Rho patterning. Efficient migration also requires polarized organization of the cell interior, with organelle positioning increasingly recognized as a key determinant of cell movement. Yet how this organization is established remains unclear. Building on our mechanochemical framework, we now investigate how actin-generated forces position organelles during migration and how disruption of this intracellular organization contributes to disease.
\r\n
\r\nWebsite of the De Belly lab: https://cri.utsw.edu/faculty/henry-de-belly/
\r\n
\r\nThis is part of the Physics of Living Systems monthly symposium: https://pols.epfl.ch/physics-of-living-systems-seminars/monthly-symposium/
Lysosomes sit at the crossroads of cellular catabolism and quality control, where they must dismantle chemically diverse cargo while preserving their own integrity. I will discuss two discoveries that reveal how lysosomes solve these complementary challenges and how their failure creates disease vulnerabilities. First, I will describe Lysosomal Leucine Aminopeptidase (LyLAP), an enzyme specialized to processively degrade the hydrophobic α-helices of transmembrane proteins. LyLAP is highly expressed in pancreatic ductal adenocarcinoma, where its loss causes hydrophobic peptides to accumulate, compromises lysosomal function, and ultimately leads to cancer cell death, revealing a potential vulnerability in tumors with elevated endocytic activity. I will then describe LASER, a damage-responsive protein assembly that couples lysosomal membrane injury to repair. At its core, the oligomeric protein TFG recognizes LC3/GABARAP proteins conjugated to damaged lysosomes and recruits the ESCRT machinery to restore membrane integrity. Neurodegenerative disease-associated mutations in TFG disrupt this process, linking defective lysosomal repair to human disease. Together, these findings reveal lysosomes as dynamic systems that coordinate cargo degradation with membrane surveillance and repair to maintain cellular homeostasis.
\r\n
\r\nMore about Dr. Aakriti Jain's lab at UTSW: https://aakritijainlab.com/
I develop a dynamic capital structure framework in which many firms supply debt without commitment, and debt prices are determined by market clearing. Corporate debt is not a standard asset with fixed supply and exogenous cash flows. Its market valuation affects debt issuance, which in turn affects aggregate debt supply, default risk, and the cash flows delivered by debt. The model shows how debt demand is an important determinant of leverage dynamics and the cross-sectional distribution of leverage. Importantly, stronger debt demand is entirely absorbed by issuance and leads to lower long-run bond prices in equilibrium. I then extend the framework to allow for imperfect substitutability across bonds. Credit rating segmentation generates leverage dynamics around rating boundaries that are consistent with empirical evidence. When investors have preferred habitats, endogenous demand and supply jointly determine maturity premia. Correlation across cash-flow shocks affects the speed of leverage adjustment and can induce firms to repurchase debt optimally.
","image_description":"","creation_date":"2026-09-01T11:07:17","last_modification_date":"2026-09-25T15:43:17","link_label":"","link_url":"","canceled":"False","cancel_reason":"","place_and_room":"UNIL, Extranef, room 126","url_place_and_room":"","url_online_room":"","spoken_languages":["https://memento.epfl.ch/api/v1/spoken_languages/2/?format=json"],"speaker":"Darius Nik-Nejad - PhD, SFI@EPFL","organizer":"","contact":"sophie.cadenakauz@epfl.ch","is_internal":"False","theme":"","vulgarization":{"id":2,"fr_label":"Public averti","en_label":"Informed public"},"registration":{"id":2,"fr_label":"Sur invitation","en_label":"Invitation required"},"keywords":"","file":null,"icalendar_url":"https://memento.epfl.ch/event/export/121643/","category":{"id":1,"code":"CONF","fr_label":"Conférences - Séminaires","en_label":"Conferences - Seminars","activated":true},"academic_calendar_category":null,"domains":[],"mementos":["https://memento.epfl.ch/api/v1/mementos/3/?format=json","https://memento.epfl.ch/api/v1/mementos/39/?format=json","https://memento.epfl.ch/api/v1/mementos/105/?format=json","https://memento.epfl.ch/api/v1/mementos/116/?format=json"]},{"id":72214,"title":"Do Robots Dream of Construction Sites? / ARCHIZOOM x CRCL","slug":"do-robots-dream-of-construction-sites-archizoom--3","event_url":"https://memento.epfl.ch/event/do-robots-dream-of-construction-sites-archizoom--3","visual_url":"https://memento.epfl.ch/image/33494/200x112.jpg","visual_large_url":"https://memento.epfl.ch/image/33494/720x405.jpg","visual_maxsize_url":"https://memento.epfl.ch/image/33494/max-size.jpg","lang":"en","start_date":"2026-09-09","end_date":"2026-12-05","start_time":null,"end_time":null,"description":"DO ROBOTS DREAM OF CONSTRUCTION SITES?