BEGIN:VCALENDAR VERSION:2.0 PRODID:icalendar-ruby CALSCALE:GREGORIAN METHOD:PUBLISH BEGIN:VTIMEZONE TZID:Europe/Vienna BEGIN:DAYLIGHT DTSTART:20260329T030000 TZOFFSETFROM:+0100 TZOFFSETTO:+0200 RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=3 TZNAME:CEST END:DAYLIGHT BEGIN:STANDARD DTSTART:20261025T020000 TZOFFSETFROM:+0200 TZOFFSETTO:+0100 RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10 TZNAME:CET END:STANDARD END:VTIMEZONE BEGIN:VEVENT DTSTAMP:20260416T010035Z UID:1770642000@ist.ac.at DTSTART:20260209T140000 DTEND:20260209T150000 DESCRIPTION:Speaker: Zuzana Dunajova\nhosted by Carrie Bernecky\nAbstract: How is self-organization in biological systems shaped by the geometry of i ndividual units and the structure of their environment? In this thesis\, w e combine minimal active-matter models with bottom-up in vitro experiments to uncover physical principles underlying emergent biological behavior ac ross scales. At the subcellular scale\, we show how the shape and mechanic s of treadmilling FtsZ filaments control large-scale pattern formation\, w hich is relevant for bacterial cytokinesis. We find that filament flexibil ity and activity-driven straightening cause a shift from chiral to nematic -like self-organization. At the cellular scale\, we investigate how cancer cells migrate through complex microenvironments. Strikingly\, we find tha t geometric disorder alone can induce a transition from collective to sing le-cell invasion and shift the universality class of interface dynamics. F inally\, we study how cell-intrinsic geometry and chirality influence coll ective motion. Using a minimal model of rotating motile cells\, we show th at confinement can promote chiral flows\, while in dense unconfined system s chirality becomes masked even before the onset of jamming transition. Ov erall\, this work uncovers how geometric constraints - embedded in the int rinsic architecture of an active filament or encoded in the complexity of a microenvironment - couple to active forces to generate different classes of complex behaviors. LOCATION:Central Bldg / O1 / Mondi 3 (I01.O1.010) \, ISTA ORGANIZER: SUMMARY:Zuzana Dunajova: Thesis Defense: Geometry-driven self-organization of migrating cells and chiral filaments URL:https://talks-calendar.ista.ac.at/events/6252 END:VEVENT BEGIN:VEVENT DTSTAMP:20260416T010035Z UID:1770710400@ist.ac.at DTSTART:20260210T090000 DTEND:20260210T100000 DESCRIPTION:Speaker: Stefan Riegler\nhosted by Beatriz Vicoso\nAbstract: Du e to their sessile nature\, plants have evolved astounding developmental p lasticity\, which allows them to respond to environmental fluctuations by adapting their growth and architecture. This adaptability is the result of the interplay between numerous hormonal and nutrient-sensing processes. B y adjusting their internal signaling pathways\, plants can optimise their resource acquisition and defense strategies\, ensuring their survival and productivity in diverse habitats.The first part of this work is centered o n the gene SYNERGISTIC ON AUXIN AND CYTOKININ1 (AtSYAC1) in Arabidopsis th aliana. Despite often antagonistic interactions between auxin and cytokini n\, AtSYAC1 exhibits a massive\, non-additive induction upon simultaneous exogenous hormone treatment. This research identifies the first biological ly relevant context that induces AtSYAC1 expression in roots\, specificall y\, phosphate starvation and plant-fungal interaction. We proceed to inves tigate the spatiotemporal expression patterns and cellular localization of AtSYAC1 in response to these cues\, discovering its specific induction in root hair cells and its potential role in root hair tip growth. By invest igating the plant-fungal relationship we highlight the high environmental sensitivity of such interactions.The second part of this thesis\, as part of the Horizon Europe BOLERO project\, addresses the development of resili ent coffee rootstocks to support sustainable\, lowinput farming systems. U sing high-throughput phenotyping and transcriptomic analyses\, the study e valuates the root system plasticity of cultivated and wild Coffea species under contrasting nitrogen supply. We identify the molecular basis of high root system plasticity in C. canephora and C. congensis\, and observe a c urious response to low nitrogen availability in C. brevipes. Furthermore\, physiological and hormonal profiling of grafted plants identifies promisi ng rootstock-scion combinations and provides a molecular and phenotypic fo undation for breeding Coffea varieties with enhanced nutrient-use efficien cy and environmental resilience.  LOCATION:Zoom\, ISTA ORGANIZER: SUMMARY:Stefan Riegler: Thesis Defense: Root System Plasticity under Nutrie nt Limitation: Investigating Hormonal and Molecular Drivers in Arabidopsis thaliana and Coffea species URL:https://talks-calendar.ista.ac.at/events/6254 END:VEVENT BEGIN:VEVENT DTSTAMP:20260416T010035Z UID:1770825600@ist.ac.at DTSTART:20260211T170000 DTEND:20260211T180000 DESCRIPTION:Speaker: Martin Dvorak\nhosted by Michael Sammler\nAbstract: Th is thesis documents a voyage towards truth and beauty via formal verificat ion of theorems. To this end\, we develop libraries in Lean 4 that present definitions and results from diverse areas of MathematiCS (i.e.\, Mathema tics and Computer Science). The aim is to create code that is understandab le\, believable\, useful\, and elegant. The code should stand for itself a s much as possible without a need for documentation\; however\, this text redundantly documents our code artifacts and provides additional context t hat isn’t present in the code. This thesis is written for readers who kn ow Lean 4 but are not familiar with any of the topics presented. We manife st truth and beauty in three formalized areas of MathematiCS.We formalize general grammars in Lean 4 and use grammars to show closure of the class o f type-0 languages under four operations\; union\, reversal\, concatenatio n\, and the Kleene star.Our second stop is the theory of optimization. Far kas established that a system of linear inequalities has a solution if and only if we cannot obtain a contradiction by taking a linear combination o f the inequalities. We state and formally prove several Farkas-like theore ms over linearly ordered fields in Lean 4. Furthermore\, we extend duality theory to the case when some coëfficients are allowed to take “infinit e values”. Additionally\, we develop the basics of the theory of optimiz ation in terms of the framework called General-Valued Constraint Satisfact ion Problems\, and we prove that\, if a Rational-Valued Constraint Satisfa ction Problem template has symmetric fractional polymorphisms of all ariti es\, then its basic LP relaxation is tight.Our third stop is matroid theor y. Seymour’s decomposition theorem is a hallmark result in matroid theor y\, presenting a structural characterization of the class of regular matro ids. We aim to formally verify Seymour’s theorem in Lean 4. First\, we b uild a library for working with totally unimodular matrices. We define bin ary matroids and their standard representations\, and we prove that they f orm a matroid in the sense how Mathlib defines matroids. We define regular matroids to be matroids for which there exists a full representation rati onal matrix that is totally unimodular\, and we prove that all regular mat roids are binary. We define 1-sum\, 2-sum\, and 3-sum of binary matroids a s specific ways to compose their standard representation matrices. We prov e that the 1-sum\, the 2-sum\, and the 3-sum of regular matroids are a reg ular matroid\, which concludes the composition direction of the Seymour’ s theorem. The (more difficult) decomposition direction remains unproved.I n the pursuit of truth\, we focus on identifying the trusted code in each project and presenting it faithfully. We emphasize the readability and bel ievability of definitions rather than choosing definitions that are easier to work with. In search for beauty\, we focus on the philosophical framew ork of Roger Scruton\, who emphasizes that beauty is not a mere decoration but\, most importantly\, beauty is the means for shaping our place in the world and a source of redemption\, where it can be viewed as a substitute for religion. LOCATION:Office Bldg West / Ground floor / Heinzel Seminar Room (I21.EG.101 ) and Zoom\, ISTA ORGANIZER: SUMMARY:Martin Dvorak: Thesis Defense: Pursuit of Truth and Beauty in Lean 4 URL:https://talks-calendar.ista.ac.at/events/6279 END:VEVENT BEGIN:VEVENT DTSTAMP:20260416T010035Z UID:1772542800@ist.ac.at DTSTART:20260303T140000 DTEND:20260303T150000 DESCRIPTION:Speaker: Thomas Werner\nhosted by Matthew Kwan\nAbstract: In th is thesis\, I investigate superconducting quantum circuits as a platform f or both fundamental tests of quantum mechanics and scalable quantum inform ation processing. Superconducting qubits are engineered electrical circuit s that exhibit discrete\, atom-like energy levels. Unlike natural atoms\, their spectra can be designed and fabricated\, enabling flexible control a t the cost of device-to-device variability. These systems operate below 10 0 mK to suppress thermal noise at their characteristic microwave frequenci es (~10 GHz). In contrast\, optical photons (~193 THz) are robust against room-temperature thermal noise and are ideal carriers of quantum informati on over long distances. Bridging these frequency regimes is therefore esse ntial for connecting superconducting quantum processors to optical quantum networks. To address this challenge\, we develop electro-optic transducer s. These devices convert single photons between the microwave and the opti cal domain. I demonstrate two proof-of-principle experiments: all-optical readout of a superconducting qubit state and upconversion of single microw ave photons to optical frequencies. These results establish a pathway towa rd integrating superconducting qubits with large-scale quantum communicati on networks. LOCATION:Sunstone Bldg / Ground floor / Big Seminar Room B (I23.EG.102) \, ISTA ORGANIZER: SUMMARY:Thomas Werner: Thesis Defense: Interfacing superconducting qubits w ith optical photons URL:https://talks-calendar.ista.ac.at/events/6316 END:VEVENT BEGIN:VEVENT DTSTAMP:20260416T010035Z UID:1773738000@ist.ac.at DTSTART:20260317T100000 DTEND:20260317T110000 DESCRIPTION:Speaker: Mirza Baig\nhosted by Julia Reisenbauer\nAbstract: Blo ckchains enable distributed consensus in permissionless settings\, where p articipants are unknown\, dynamically changing\, and do not trust each oth er. While Bitcoin\, based on Proof-of-Work (PoW)\, was the first protocol in this model\, significant research has focused on permissionless protoco ls using alternative physical resources\, specifically Proof-of-Space (PoS pace) and Verifiable Delay Functions (VDFs). This thesis investigates the theoretical limits and design space of longest-chain protocols in the full y permissionless and dynamically available settings using these three reso urces. First\, we address the feasibility of blockchains relying solely on storage as a resource. We prove a fundamental impossibility result: there exists no secure longest-chain protocol based exclusively on Proof-of-Spa ce in the fully permissionless or dynamically available settings. Further\ , we quantify the adversarial capabilities required to execute a double-sp end attack. Our result formally justifies the necessity of coupling PoSpac e with time-dependent primitives (such as VDFs) or to move to less permiss ive settings (quasi-permissionless or permissioned) to ensure security.Sec ond\, we generalize Nakamoto-like heaviest chain consensus to protocols ut ilizing combinations of multiple physical resources. We analyze chain sele ction rules governed by a weight function Γ(S\, V\,W)\, which assigns wei ght to blocks based on recorded Space (S)\, VDF speed (V )\, and Work (W). We provide a complete classification of secure weight functions\, proving that a weight function is secure against private double-spend attacks if and only if it is homogeneous in the timed resources (V\,W) and sub-homoge neous in S. This framework unifies existing protocols like Bitcoin and Chi a under a single theoretical model and provides a powerful tool for design ing new longest-chain blockchains from a mix of physical resources. LOCATION:Moonstone Bldg / Ground floor / Seminar Room C (I24.EG.030c) and Z oom\, ISTA ORGANIZER: SUMMARY:Mirza Baig: Thesis Defense: On Secure Chain Selection Rules from Ph ysical Resources in a Permissionless Setting URL:https://talks-calendar.ista.ac.at/events/6331 END:VEVENT BEGIN:VEVENT DTSTAMP:20260416T010035Z UID:1774011600@ist.ac.at DTSTART:20260320T140000 DTEND:20260320T150000 DESCRIPTION:Speaker: Tobias Kleinhanns\nhosted by Jorryt Matthee\nAbstract: Thermoelectric (TE) technology directly converts between heat and electri city\, enabling both waste heat harvesting and localized cooling applicati ons. Yet\, TE technology remains limited to niche applications\, mostly du e to high fabrication costs\, and lower efficiencies compared to other ene rgy conversion technologies. Solution processing provides a scalable and c heaper route than conventional solid-state methods\, potentially enabling the broader adoption of TE technology. Beyond its cost benefits\, solution processing uniquely allows the synthesis of well-defined nanocrystal buil ding blocks\, translating nanoscale defect control into bulk structures. S uch microstructure engineering across length scales allows rational optimi zation of the TE performance. This thesis explores defect engineering of s olution-processed silver selenide (Ag2Se)\, with focus on compositional an d microstructural control for enhanced TE performance\, specifically throu gh thiol-amine based synthesis and post-synthetic treatment using polyanio nic CdSe complexes. The material library was extended to lead selenide (Pb Se)\, whose TE performance was optimized through chlorine (Cl) doping from functionalized two-dimensional titanium carbides (MXenes). LOCATION:Sunstone Bldg / Ground floor / Big Seminar Room B (I23.EG.102) \, ISTA ORGANIZER: SUMMARY:Tobias Kleinhanns: Thesis Defense: Unraveling the Origin and Evolut ion of Defects to Enable Advanced Thermoelectric Performance URL:https://talks-calendar.ista.ac.at/events/6341 END:VEVENT BEGIN:VEVENT DTSTAMP:20260416T010035Z UID:1776081600@ist.ac.at DTSTART:20260413T140000 DTEND:20260413T150000 DESCRIPTION:Speaker: Ksenia Khudiakova\nhosted by Mikhail Lemeshko\nAbstrac t: This Ph.D. thesis investigates how different forms of selection shape g enetic diversity in a constant environment that has led to evolutionary eq uilibrium. We progress from a non-epistatic case to increasingly complex m odels of epistasis and rely on stochastic and deterministic theory togethe r with simulations.We first show that in the non-epistatic case\, and in a n asexual population\, weak purifying selection leads to multiple-merger g enealogies\, and that the transition in genealogical properties coincides with the onset of Muller’s ratchet.Then\, we apply a result from discret e Morse theory to prove that adding each next fitness peak to the landscap e requires at least one additional special pairwise interaction between lo ci\, called reciprocal sign epistasis.We then show that reciprocal sign ep istasis can extend the diversity-promoting effects of balancing selection and delineate the parameter conditions under which this effect is expected to occur.Finally\, we demonstrate how epistasis that arises under stabili zing selection amplifies the effects of random genetic drift by causing th e selection coefficients of mutations to fluctuate through interactions wi th the changing genetic background.Together\, these results show that non- epistatic purifying selection reduces genetic diversity relative to neutra lity\, and that once Muller’s ratchet starts operating\, this reduction cannot be captured by any simple rescaling of Kingman’s coalescent. On a n epistatic fitness landscape\, reciprocal sign epistasis is a key ingredi ent for generating multiple fitness peaks\, and it substantially alters wi thin-population dynamics at evolutionary equilibrium by extending the dive rsity-maintaining effects of balancing selection and driving temporal chan ges in selection coefficients. This Ph.D. thesis thus advances our underst anding of how epistasis shapes genetic diversity and evolutionary dynamics in populations at equilibrium. LOCATION:Sunstone Bldg / Ground floor / Big Seminar Room B (I23.EG.102) and Zoom\, ISTA ORGANIZER: SUMMARY:Ksenia Khudiakova: Thesis Defense: How epistasis and purifying sele ction shape genetic diversity URL:https://talks-calendar.ista.ac.at/events/6399 END:VEVENT BEGIN:VEVENT DTSTAMP:20260416T010035Z UID:1776672000@ist.ac.at DTSTART:20260420T100000 DTEND:20260420T110000 DESCRIPTION:Speaker: Eugenia Iofinova\nhosted by Samara Ren\nAbstract: As n eural-network-based models grow both in size and popularity\, interest has grown in making the models smaller and more efficient to train. To that e nd\, many methods have been proposed to prune models by reducing their num ber of nonzero parameters. Additionally\, parameter-efficient fine-tuning\ , in which a much smaller number of parameters than the total contained in the model is updated during training\, has become very popular\, especial ly in the space of Large Language Models. At the same time\, the increasin gly routine deployment of machine learning in real-world applications has spurred a drive to make them more trustworthy - in the sense of\, among ot her things\, being unbiased\, interpretable\, and editable. In this thesis \, we examine the interplay between efficiency and trustworthiness.First\, we analyze the effects of model pruning on bias in computer vision models \, demonstrating that increased sparsity leads to greater bias\, largely a s a function of increased model uncertainty in marginal cases. Based on th is observation\, we propose several bias mitigation techniques. Then\, we demonstrate that example-specific model pruning can improve model interpre tation methods while improving pruning efficiency to make example-specific model pruning feasible in real time. Then\, we investigate the effectiven ess of parameter-efficient and data-efficient model personalization via fi ne-tuning\, demonstrating that it is highly feasible with very small compu tational and data resources. Finally\, we consider efficiency in editing m odel knowledge using a custom synthetic data framework\, demonstrating tha t parameter-efficient\, low-rank fine-tuning frequently outperforms full-r ank fine-tuning\, and\, additionally\, restricting fine-tuning to specific model blocks frequently improves results. Together\, the results in this thesis provide new insights and techniques for combining trustworthiness a nd efficiency during neural network inference and training. LOCATION:Office Bldg West / Ground floor / Heinzel Seminar Room (I21.EG.101 ) and Zoom\, ISTA ORGANIZER: SUMMARY:Eugenia Iofinova: Thesis Defense: On the Utility and Effects of Eff iciency in Artificial Neural Networks URL:https://talks-calendar.ista.ac.at/events/6391 END:VEVENT END:VCALENDAR