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:20260711T010058Z 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:20260711T010058Z 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 BEGIN:VEVENT DTSTAMP:20260711T010058Z UID:1778065200@ist.ac.at DTSTART:20260506T130000 DTEND:20260506T160000 DESCRIPTION:Speaker: David Vijatovic\nhosted by Amelia Douglass\nAbstract: Motor circuits must generate distinct patterns of movement while adapting to developmental changes in body form and behavioral demands. Frog metamor phosis provides a unique opportunity to study this process\, as Xenopus la evis transitions from axial\, tail-based swimming to limb-based locomotion . This work investigates how spinal circuits are molecularly organized and functionally reorganized during this transition.I examine how spinal neur on composition changes across metamorphosis\, showing that cell type diver sity increases with the emergence of limb movement. In particular\, inhibi tory V1 interneurons and motor neurons expand and diversify into transcrip tionally defined populations resembling those described in mammals. These findings support conserved organizational principles of vertebrate spinal circuits and link cell type diversification to the emergence of more compl ex motor behaviors. I further develop viral and optical approaches to prob e how these molecularly defined circuits are functionally reorganized duri ng this transition.Together\, these findings establish Xenopus laevis as a powerful model for linking molecular identity\, circuit dynamics\, and be havior across vertebrate development. LOCATION:Sunstone Bldg / Ground floor / Big Seminar Room A / 27 seats (I23. EG.102)\, ISTA ORGANIZER: SUMMARY:David Vijatovic: Thesis Defense:Dissecting molecular and functional basis of motor control in Xenopus laevis frog URL:https://talks-calendar.ista.ac.at/events/6442 END:VEVENT BEGIN:VEVENT DTSTAMP:20260711T010058Z UID:1779458400@ist.ac.at DTSTART:20260522T160000 DTEND:20260522T170000 DESCRIPTION:Speaker: Jeferson Zapata\nhosted by Matthew Kwan\nAbstract: Sta ndard mathematical optimization and root-finding algorithms often stall or fail when faced with degenerate or singular problems. This thesis present s novel symbolic-numeric frameworks designed to overcome these theoretical and computational bottlenecks. The first part of the presentation introdu ces a hybrid algorithm that reformulates weakly feasible\, degenerate semi definite programs (SDPs) into structured polynomial systems\, enabling the rigorous algebraic certification of numerical approximations. The second part addresses the loss of convergence in path-tracking methods near isola ted singular roots. By modeling solution paths as generalized fractional P uiseux series and utilizing an explicitly derived algebraic predictor\, th e proposed algorithms restore superlinear convergence and significantly re duce computational overhead in heavily degenerate systems. LOCATION:Office Bldg West / Ground floor / Heinzel Seminar Room (I21.EG.101 ) and Zoom\, ISTA ORGANIZER: SUMMARY:Jeferson Zapata: Thesis Defense: Overcoming Degeneracy and Singular ity: Techniques for Semidefinite Programs and Homotopy Continuation Endgam es URL:https://talks-calendar.ista.ac.at/events/6476 END:VEVENT BEGIN:VEVENT DTSTAMP:20260711T010058Z UID:1780488000@ist.ac.at DTSTART:20260603T140000 DTEND:20260603T150000 DESCRIPTION:Speaker: Antoine El-Hayek\nhosted by Georgios Katsaros\nAbstrac t: Networks can change over time. Whether it is the Facebook network\, whe re 'friendships' emerge or end\, the internet\, where computers connect or disconnect from the network\, or the train network\, where new lines can be created or canceled. This creates specific challenges for algorithms de signed to either run or manage these 'dynamic' networks.A distributed algo rithm is an algorithm that runs on the network. Think of the internet: for computers to communicate through this network\, the algorithm should be i nstalled on both computers\, and both computers won't necessarily have acc ess to the same information. If the network is unstable\, or is simply dyn amic\, the communication between them can drop at any point\, and the algo rithm should be robust to such changes. In this model\, we look at two pro blems: the broadcast problem\, where one computer tries to send a message to every single other computer on the network\, and the majority problem\, where initially each computer is given an opinion among k possible ones\, and the goal is for every computer to know which opinion was originally t he most popular one.A dynamic graph algorithm is an algorithm that manages a dynamic network\, or computes a property on it. Think of the network of webpages. You might want to rank all webpages from the most important one to the least (popular search engines call it the 'PageRank' algorithm). H owever\, every day\, new pages go online\, while old pages go offline. You wouldn't want the algorithm to be run from scratch every night over all o nline webpages\, as this would cost too much energy. Instead\, you would l ike to have an algorithm that\, once it has computed the rank of each webp age at a given time\, be able to handle a few changes\, and update its sol ution accordingly. In the dynamic graph algorithm model\, we look at the m inimum cut problem\, where the goal is is divide the network into two subn etworks\, such that the number of connections from one subnetwork to the o ther is minimized. LOCATION:Moonstone Bldg / Ground floor / Seminar Room F (I24.EG.030f) and Z oom\, ISTA ORGANIZER: SUMMARY:Antoine El-Hayek: Thesis Defense: Handling Updates and Failures: Dy namic Graph Algorithms and Distributed Computing on Dynamic Networks URL:https://talks-calendar.ista.ac.at/events/6452 END:VEVENT BEGIN:VEVENT DTSTAMP:20260711T010058Z UID:1781607600@ist.ac.at DTSTART:20260616T130000 DTEND:20260616T140000 DESCRIPTION:Speaker: Konstantin Kueffner\nhosted by Krzysztof Pietrzak\nAbs tract: As automated decision-makers have become ubiquitous in many domains of life\, their decisions have become increasingly consequential. Recent years have shown that such systems can exhibit discriminatory behaviour ag ainst individuals and social groups alike\, thereby amplifying existing bi ases and entrenching socio-economic disparities over time. Algorithmic fai rness addresses this problem by developing methods to quantify and mitigat e unfair behaviour. However\, much of the existing literature studies fair ness in a static pre-deployment setting and\, therefore\, neglects that au tomated decision-makers are often deployed in dynamic environments\, where their behaviour and the populations they affect may change over time.This thesis addresses this gap through the lens of runtime verification. Inste ad of treating fairness as a property of a classifier together with a fixe d input distribution\, it reframes fairness as a property of the interacti on trace between the decision-maker and its deployment environment. To eva luate such sequential fairness properties\, the thesis develops runtime mo nitors that observe the evolving interaction between the system and the en vironment and issue verdicts after each new observation. Because\, these m onitors are designed to detect unfair behaviour during deployment\, they c omplement fair training\, auditing\, verification\, and enforcement by pr oviding an additional layer of mathematically rigorous fairness assurance. In summary\, the thesis develops quantitative\, trace-based analogues of c lassical group and individual fairness measures and constructs monitors fo r them. This includes monitors for long-run group fairness over Markovian traces\, for the time-varying welfare of a changing population in a dynami cal system\, and for the individual fairness of an arbitrary system genera ting a trace of inputs and outputs. To achieve this\, the monitors combine ideas from runtime verification\, sequential statistics\, and nearest-nei ghbour search. In the group-fairness settings\, monitoring is primarily a sequential statistical estimation problem: the monitor must construct stat istically sound interval estimates of fairness values from dependent and p artially observed interactions. In the individual-fairness setting\, the m ain challenge is computational efficiency: the monitor must detect individ ual fairness violations by efficiently comparing the current decision with all previously observed decisions. LOCATION:Central Bldg / O1 / Mondi 3 (I01.O1.010) and Zoom\, ISTA ORGANIZER: SUMMARY:Konstantin Kueffner: Thesis Defense: Monitoring Algorithmic Fairnes s in Sequential Decision Making URL:https://talks-calendar.ista.ac.at/events/6480 END:VEVENT BEGIN:VEVENT DTSTAMP:20260711T010058Z UID:1781702100@ist.ac.at DTSTART:20260617T151500 DTEND:20260617T161500 DESCRIPTION:Speaker: Yunzhe Li\nhosted by Maksym Serbyn\nAbstract: We study spectral rigidity and nonrigidity phenomena in dynamical systems. The cen tral question is whether a dynamical system can be determined\, up to a na tural conjugacy\, by its spectrum.The first part of the talk focuses on st andard maps from the viewpoint of action spectra. We construct nontrivial deformations of the standard map that preserve the symplectic actions of i nfinitely many periodic orbits accumulating onto an invariant curve. This result can be viewed as a symplectic twist-map analogue of length-spectral nonrigidity phenomena for Riemannian manifolds and convex billiards\, mot ivating the problem of constructing analogous “partially length-isospect ral” deformations of strictly convex billiard tables. The proof combines a resonant normal form construction with Picard iteration schemes to prod uce a sequence of periodic orbits accumulating on an invariant curve with a Liouville rotation number. The second part of the talk briefly explores rigidity questions for Liouville metrics on the two-dimensional torus. A long-standing folklore conjecture asserts that Liouville metrics are the o nly integrable metrics on the torus. We give a length-spectral rigidity re sult for the class of trigonometric conformal deformations of Liouville me trics by exploiting the dynamical properties of rational tori\, which are analogues of resonant convex caustics in billiards. We also establish a co mplementary classification result showing that marked-length-isospectral L iouville metrics are characterized by rearrangements of the one-dimensiona l functions appearing in their conformal factors\, generalizing a theorem of Abbondandolo and Mazzucchelli. In particular\, this result yields many nonrigidity examples within the class of Liouville metrics. LOCATION:Office Bldg West / Ground floor / Heinzel Seminar Room (I21.EG.101 ) and Zoom\, ISTA ORGANIZER: SUMMARY:Yunzhe Li: Thesis Defense: Spectral Rigidity and Nonrigidity of Dyn amical Systems URL:https://talks-calendar.ista.ac.at/events/6506 END:VEVENT BEGIN:VEVENT DTSTAMP:20260711T010058Z UID:1782201600@ist.ac.at DTSTART:20260623T100000 DTEND:20260623T110000 DESCRIPTION:Speaker: Lea Becker\nhosted by Robert Seiringer\nAbstract: Char acterizing protein dynamics at the atomic level is essential for our under standing of biological mechanisms. Whether it is to facilitate metabolite transport\, catalyze reactions\, transmit signals\, or regulate metabolism – proteins are constantly in motion and sample multiple conformational states to fulfill their function. Nuclear magnetic resonance (NMR) spectro scopy is particularly well suited to elucidate the dynamics of biomolecule s on their complex free-energy landscape. In particular\, solid-state magi c-angle spinning (MAS) NMR enables the study of large molecular assemblies \, protein crystals\, or insoluble proteins at atomic resolution without a n inherent molecular size limitation. MAS NMR experiments to probe protein dynamics are extremely versatile and sensitive to motional timescales fro m picoseconds to seconds. Over the past decades\, technological advances\, developments in experimental design\, and new isotope-labeling approaches have further expanded the possibilities of this technique and significant ly improved the accuracy of the determined motional parameters.Functionall y important sites of proteins often contain aromatic residues. Their side- chain motions have therefore long served as valuable indicators of mechani stically relevant dynamics in NMR studies. In this thesis\, site-specifica lly labeled aromatic residues act as sensitive reporters for MAS NMR studi es of protein dynamics. The first part addresses how different environment s impact side-chain motion by probing ring flips of phenylalanines and tyr osines in crystalline proteins and amyloid fibrils. It provides important insights for the analysis of dynamics obtained in non-native protein envir onments and emphasizes the complex factors that determine the timescale of internal dynamics. In the second part\, the focus shifts towards methodol ogical questions regarding the investigation of protein dynamics by 19F MA S NMR. The fluorine nucleus exhibits promising characteristics for NMR stu dies but also presents significant challenges\, which is why the full meth odological potential of 19F MAS NMR has not been fully realized yet. This work demonstrates that paramagnetic doping can considerably reduce the mea surement time and improve the sensitivity of fluorinated samples. Finally\ , 19F MAS NMR is evaluated as a tool for studying protein side-chain dynam ics on the example of tryptophans. The results illustrate the challenges i n analyzing such experiments and lay the foundation for further developmen t of 19F MAS NMR relaxation studies.Taken together\, this thesis highlight s the potential of combining specific isotope labeling\, MAS NMR\, and com plementary methods such as crystallography and computational simulations t o elucidate internal protein dynamics. The further development of such int egrative approaches will be crucial to improving our understanding of comp lex mechanisms and protein function. LOCATION:Central Bldg / O1 / Mondi 2a (I01.O1.008)\, ISTA ORGANIZER: SUMMARY:Lea Becker: Thesis Defense: Exploring protein dynamics using specif ic labeling approaches for solid-state MAS NMR URL:https://talks-calendar.ista.ac.at/events/6447 END:VEVENT BEGIN:VEVENT DTSTAMP:20260711T010058Z UID:1782720000@ist.ac.at DTSTART:20260629T100000 DTEND:20260629T110000 DESCRIPTION:Speaker: Jakub Löwit\nhosted by Krishnendu Chatterjee\nAbstrac t: We develop and employ techniques from equivariant algebraic K-theory an d related invariants in the context of geometric representation theory\, i n both arithmetic and topological situations. We showcase the use of such techniques on the affine Grassmannian Gr\, a space of fundamental interest in the geometric Langlands program. LOCATION:Office Bldg West / Ground floor / Heinzel Seminar Room (I21.EG.101 ) and Zoom\, ISTA ORGANIZER: SUMMARY:Jakub Löwit: Thesis Defense: Equivariant K-theory of affine Grassm annians in representation theory and arithmetic URL:https://talks-calendar.ista.ac.at/events/6500 END:VEVENT BEGIN:VEVENT DTSTAMP:20260711T010058Z UID:1782918000@ist.ac.at DTSTART:20260701T170000 DTEND:20260701T180000 DESCRIPTION:Speaker: Simone Bombari\nhosted by Matthew Kwan\nAbstract: Arti ficial intelligence and machine learning have undergone an unprecedented e volution in the past decade\, motivating a research effort toward a theory able to capture the qualitative behavior of large-scale neural systems. A central puzzle has been the clear benefit of scaling architecture size an d overfitting the training set in supervised learning tasks. This evidence \, in apparent contradiction with classical statistical learning theory\, pushed researchers to develop a new theory capturing the interplay between the algorithmic and architectural bias of training and the specific targe t function\, differently from previous methods rooted in uniform stability .This approach has enabled a grounded understanding of novel learning regi mes\, typically through formal limits where the number of training samples $n$\, data dimensions $d$\, and model parameters $p$ grow to infinity at different rates.In this thesis\, we follow this approach\, focusing on the trustworthiness of high-dimensional models: properties that are difficult to control during training or deployment and often emerge under unpredict able or adversarial conditions. In such settings\, it is crucial to formal ly ensure a priori the reliability of machine learning systems.First\, we study data memorization\, both as label fitting and as the storage of priv ate information about training samples in trained parameters. We prove tha t $p = \\Omega(n)$ parameters are sufficient for a deep neural network to memorize a generic set of labels\, and for a model to memorize spurious fe atures across training data. We then give evidence that $p = \\Omega(dn)$ parameters are instead necessary for an adversary to reconstruct the full training set from the trained parameters.Second\, we study robustness\, bo th to adversarial perturbations and to distribution shift. We first prove that $p = \\Omega(dn)$ parameters can be sufficient for a class of neural networks to overfit the training data while guaranteeing robustness to adv ersarial perturbations. Then\, we focus on spurious correlations learning in high-dimensional regression\, studying the effect of the ridge regulari zation parameter in the proportional regime $n = \\Theta(d)$\, and connect ing it via an equivalence argument to the role of over-parameterization $p = \\Omega(n)$ in neural networks. We also investigate the architectural b ias of attention-based networks\, showing that they are sensitive to the r eplacement of individual words in an embedded sentence\, allowing them to generalize on sentences where the contextual meaning depends on one or few words.Finally\, we study differentially private optimization in high-dime nsional regimes. We prove that standard private gradient methods do not su ffer in the over-parameterized regime $p = \\Omega(n)$\, challenging the c urrent wisdom based on stability-derived generalization bounds. We then co nsider linear regression in the proportional regime $n = \\Theta(d)$\, sho wing that standard private gradient descent can achieve optimal rates unde r appropriate hyper-parameter scaling\, such as sufficiently small gradien t clipping constants\, whose role is still debated in practice. LOCATION:Office Bldg West / Ground floor / Heinzel Seminar Room (I21.EG.101 ) and Zoom\, ISTA ORGANIZER: SUMMARY:Simone Bombari: Thesis Defense: Trustworthy Machine Learning in Hig h Dimensions URL:https://talks-calendar.ista.ac.at/events/6499 END:VEVENT BEGIN:VEVENT DTSTAMP:20260711T010058Z UID:1783076400@ist.ac.at DTSTART:20260703T130000 DTEND:20260703T140000 DESCRIPTION:Speaker: Xin Tong\nhosted by Carl Goodrich\nAbstract: Embryo cl eavage — a series of rapid\, reductive cell divisions — is the first m orphogenetic movement following fertilisation. It lays the foundation for subsequent developmental events\, including gastrulation\, germ layer spec ification\, organogenesis\, and the establishment of the overall body plan . Two major modes of cleavage exist in the animal kingdom: holoblastic (co mplete) and meroblastic (incomplete) cleavage. Because holoblastic cleavag e resembles canonical cytokinesis\, its biochemical and mechanical basis h as been extensively studied — an annular contractile ring forms at the e quator and constricts in a purse-string-like manner\, leading to the compl ete separation of two daughter cells. In contrast\, although meroblastic c leavage occurs widely across the animal kingdom (e.g. in fish\, reptiles\, birds\, and cephalopod molluscs)\, its mechanical basis remains largely u nclear. During meroblastic cleavage\, the cytokinetic furrow forms only at one pole and does not traverse the entire embryo\, raising the question o f how cytokinesis proceeds in the absence of a closed contractile ring. Mo reover\, the resulting daughter cells are not fully separated from the und erlying yolk compartment\, and how these blastomeres are subsequently cell ularised remains unknown. This thesis takes the zebrafish as a model organ ism to address both questions. The first part characterises the biochemica l and mechanical mechanisms underlying non-canonical meroblastic cleavage\ , revealing a two-phase process in which actomyosin cable contraction and cadherin-mediated membrane adhesion act sequentially to drive furrow ingre ssion and invagination. The second part sheds light on the spatiotemporal dynamics by which individual blastomeres become cellularised\, and uncover s a previously unrecognised contribution of central blastomeres to the yol k syncytial layer. LOCATION:Central Bldg / O1 / Mondi 3 (I01.O1.010) \, ISTA ORGANIZER: SUMMARY:Xin Tong: Thesis Defense: Towards a deeper understanding of merobla stic cleavage - biochemical mechanisms of partial cytokinesis and cellular ization in zebrafish embryogenesis URL:https://talks-calendar.ista.ac.at/events/6519 END:VEVENT BEGIN:VEVENT DTSTAMP:20260711T010058Z UID:1783598400@ist.ac.at DTSTART:20260709T140000 DTEND:20260709T150000 DESCRIPTION:Speaker: David Michalik\nhosted by Eva Benková\nAbstract: MDA5 is an antiviral protein that is activated by long dsRNA molecules. This R NA can be of various origins such as viral\, bacterial\, synthetic or\, up on certain stimuli\, even cellularsources. Upon sensing immunogenic RNA\, MDA5 coats the dsRNA\, forming a filament. Filament formation brings CARD domains into close proximity\, resulting in CARD oligomerisation. These ol igomers are not involved in the RNA recognition but are crucial for activa tion of downstream signalling. MDA5 activation leads to a type I interfero n response and apoptosis. Loss of function mutations are linked to recurre nt\, life-threatening viral infections whereas gain of function mutations are linked to monogenic and polygenic autoimmune diseases. For these reaso ns\, MDA5 needs to be tightly regulated by various mechanisms including po st-translational modifications\, post-transcriptional modifications\, and protein-protein interactions. In the first chapter\, we focused on the cha racterisation of novel phosphorylation sites in MDA5. Using biochemistry\, molecular dynamics simulations\, virology\, cell biology and mass spectro metry\, we characterised two phosphorylation sites that altered MDA5 activ ity andwere regulated in cells upon EMCV infection or IFN-β treatment. Fu rthermore\, we discovered an additional phosphorylation site in a non-cons erved region\, which is upregulated under both stimuli.In the second chapt er\, we focused on biochemical\, biophysical\, and structural characterisa tion of various RNAs and MDA5 filaments assembled on them. We discovered t hat poly I:C\, a synthetic RNA used to activate an immune response in cell s\, has distinct physicochemical characteristics and is not a true mimic o f viral RNA\, as is often described. Additionally\, we used cryogenic elec tron microscopy to gain structural insights into which RNA features define a strong activator of MDA5. To address this\, we compared poly I:C to pol y A:U\, an RNA that does not activate an MDA5 signalling in cells\, and to a virus-derived dsRNA. In the last chapter\, we focused on activators of MDA5 signalling. In the first part\, we present our efforts to isolate and identify a small molecule agonist of MDA5. In the last part\, we describ ed our contribution to a collaborative project during which we characteris ed the interaction of ANXA2 with MDA5 and activation of MDA5 by a small mo lecule. LOCATION:Office Bldg West / Ground floor / Foyer seminar room (I21.EG.128)\ , ISTA ORGANIZER: SUMMARY:David Michalik: Thesis Defense: Mechanistic insights into MDA5 sele ctivity and regulation URL:https://talks-calendar.ista.ac.at/events/6508 END:VEVENT BEGIN:VEVENT DTSTAMP:20260711T010058Z UID:1784278800@ist.ac.at DTSTART:20260717T110000 DTEND:20260717T120000 DESCRIPTION:Speaker: Christine Fiedler\nhosted by Edouard Hannezo\nAbstract : Thermoelectric materials can directly convert between heat and electrici ty\, offering a route toward sustainable energy generation. However\, thei r use remains limited to niche applications due to high fabrication costs and relatively low efficiencies compared to competing energy technologies. Tin chalcogenides such as SnSe and SnS are promising candidates and\, whe n processed via solution-based routes\, provide a scalable and lower-cost alternative to conventional solid-state synthesis\, opening pathways towar d broader adoption. However\, realizing their full potential in polycrysta lline form requires a deeper understanding of how defects\, dopants\, and microstructure govern charge and heat transport.This thesis demonstrates t hat\, in solution-processed materials\, dopants including those introduced unintentionally through precursor chemistry\, are not just confined to sp ecific lattice sites. Instead\, they distribute across the microstructure\ , partitioning within grain interiors\, grain boundaries\, and segregated regions\, where they govern grain growth\, carrier concentration\, and cha rge transport. Through a systematic study of alkali metals and lead halide s in SnSe and SnS\, this work links synthesis\, defect partitioning\, micr ostructure evolution\, and thermoelectric performance reshaping how high-p erformance p- and n-type thermoelectric materials are designed. LOCATION:Sunstone Bldg / Ground floor / Big Seminar Room B (I23.EG.102) and Zoom\, ISTA ORGANIZER: SUMMARY:Christine Fiedler: Thesis Defense: Mechanistic Insight into Solutio n-Processed P-type Tin Chalcogenides as a Basis for Designing their N-type Analogs URL:https://talks-calendar.ista.ac.at/events/6530 END:VEVENT BEGIN:VEVENT DTSTAMP:20260711T010058Z UID:1785229200@ist.ac.at DTSTART:20260728T110000 DTEND:20260728T120000 DESCRIPTION:Speaker: Miguel Cueto Noval\nhosted by Carrie Bernecky\nAbstrac t: The widespread adoption of apps like Whatsapp and Signal has translated into billions of people all around the world communicating on a regular b asis by making use of services that offer end-to-end encryption and even p rovide security guarantees when a user's device is compromised.This was ma de possible by the introduction of the Double Ratchet Algorithm\, which wa s designed for a setting where communication takes place between two parti es. However\, in practice\, many apps offer the possibility of creating gr oups. The protocols they use to secure communication are inefficient for l arge group which has the undesirable consequence that the aforementioned a pps have established limits on the group size of roughly 1000 users. This has motivated the introduction of the Messaging Layer Security (MLS) stand ard by the IETF which is based on a primitive called Continuous Group Key Agreement (CGKA).This primitive allows a group of users to maintain a shar ed secret key that is frequently rotated by the group members in order to change group membership\, achieve forward secrecy (FS) and post compromise security (PCS). Most protocols are based on binary trees where the nodes are associated to a pair formed by public key and a secret key. Each leaf corresponds to one of the group members and a user knows the secret keys a ssociated to nodes along the path from their leaf to the root. When a user wants to update their key material they have to change $ \\log(N) $ many keys. This requires uploading $ \\log(N) $ many ciphertexts to communicate the new keys to the rest of the group members in a way that respects the tree structure.In this thesis we study how much communication between grou p members is required in order to add and remove users from a group as wel l as in order to provide PCS when we consider CGKAs built using standard c ryptographic primitives like pseudo-random functions and public-key encryp tion. Furthermore\, we also consider the case of MLS and provide the first lower bound showing that its communication complexity is much worse than previously believed\, i.e.\, it is very far from $ \\log(N) $. Finally\, w e also propose a variant of MLS which provably achieves the same security properties with a much lower communication cost. LOCATION:Moonstone Bldg / Ground floor / Seminar Room C (I24.EG.030c ) and Zoom\, ISTA ORGANIZER: SUMMARY:Miguel Cueto Noval: Thesis Defense: Towards Efficient Secure Group Messaging URL:https://talks-calendar.ista.ac.at/events/6544 END:VEVENT BEGIN:VEVENT DTSTAMP:20260711T010058Z UID:1785744000@ist.ac.at DTSTART:20260803T100000 DTEND:20260803T110000 DESCRIPTION:Speaker: Felix Pertl\nhosted by Georgios Katsaros\nAbstract: Co ntact electrification (CE) is a simple yet elusive phenomenon that occurs when two materials come into contact and separate\, leaving behind net ele ctrical charge. Despite its ubiquity\, the microscopic origin of CE remain s unclear. In this thesis\, we investigate CE from three complementary per spectives: developing a quantitative method to measure charge at the nanos cale\, exploring the dynamic behavior of charge on insulating surfaces\, a nd uncovering the role of mechanical history in forming a triboelectric se ries.In the first part\, we establish a rigorous framework for converting qualitative Kelvin probe force microscopy (KPFM) voltage maps into quantit ative charge density distributions. Using finite element method (FEM) simu lations\, we determine the point-spread function of the KPFM tip–sample geometry and demonstrate that the true surface charge can be reconstructed by numerical deconvolution. This procedure enables the recovery of both t he magnitude and sign of charge density with high fidelity\, resolving nan oscale features that are otherwise obscured. Applying the method to contac t-charged SiO$_2$ surfaces\, we show that existing analytical approximatio ns\, such as parallel plate or spherical models\, can miscalculate charge magnitude by orders of magnitude. Our hybrid FEM/KPFM approach therefore p rovides a fast and general method to convert qualitative KPFM signals into quantitative charge data\, enabling nanoscale charge mapping under realis tic experimental conditions.In the second part\, we study the temporal sta bility of CE-induced charges and identify the key material factors that de termine whether KPFM can capture meaningful charge patterns. Through time- resolved experiments combining a custom-built transfer system with both mi croscopic and macroscopic measurements\, we demonstrate that only the best insulators\, such as SiO$_2$\, preserve CE charge long enough for station ary imaging. For less conductive polymers\, such as PDMS\, charge decays w ithin the duration of a single KPFM scan due to bulk conduction. Using a s imple capacitor-based model\, we reproduce the observed decay dynamics and confirm that the transferred charge decays characteristic to the sample's bulk conductivity. Further\, we always observe homogeneous charge transfe r.In the third part\, we address the question: can we form a triboelectric series with identical materials? Using controlled repetitive contact expe riments\, we show that nominally identical materials can progressively ord er themselves into a triboelectric series\, where surfaces with more conta ct history charge negatively relative to fresher ones. By constructing a m inimal model based on this contact bias''\, we replicate the evolution fro m random to ordered charging observed in experiments. Supporting surface a nalyses\, including atomic force microscopy\, reveal that repeated contact induces nanoscale morphological changes\, suggesting a mechanism tightly coupled to mechanical strain. These results highlight the crucial role of surface history and nanoscale mechanics in dictating charge transfer\, mot ivating further exploration of mechanisms such as mechanochemical bond cle avage and flexoelectric polarization. LOCATION:Sunstone Bldg / Ground floor / Big Seminar Room B (I23.EG.102) and Zoom\, ISTA ORGANIZER: SUMMARY:Felix Pertl: Thesis Defense: Experimental probing of nanoscale char ge features and surface morphology changes during tribocharging URL:https://talks-calendar.ista.ac.at/events/6537 END:VEVENT BEGIN:VEVENT DTSTAMP:20260711T010058Z UID:1785744000@ist.ac.at DTSTART:20260803T100000 DTEND:20260803T110000 DESCRIPTION:Speaker: Marek Randuch\nhosted by Michael Sixt\nAbstract: Root growth inhibition (RG) by auxin and other cues (e.g. eATP\, RALF peptide) involves rapid\, non-transcriptional pathways. Specific steps leading to g rowth inhibition are unclear. Notably\, the RG inhibition is associated wi th increases in cytosolic Ca2+\, plasma membrane depolarization and apopla st alkalization. However\, the causal relationship between them is unclear . To untangle these processes\, we utilized multiplexed reporter imaging to observe pairwise the real-time dynamics of these three processes. Furth ermore\, we tested causal relationships. We employed microfluidics for rap id medium exchange and leveraged new optogenetically regulated channels.  Our comprehensive approach uncovered a network with tight feedback loops. Results indicate that cytosolic Ca2+ serves as the universal initial signa l\, triggering both plasma membrane depolarization and subsequent apoplast alkalization following auxin perception. his conclusion provides a basis for the fundamental regulatory mechanism governing growth but also opens q uestions about the molecular mechanisms behind it. LOCATION:Office Bldg West / Ground floor / Heinzel Seminar Room (I21.EG.101 ) and Zoom\, ISTA ORGANIZER: SUMMARY:Marek Randuch: Thesis Defense: Fast growth responses in plants: Pho spho‐proteomic and growth regulation URL:https://talks-calendar.ista.ac.at/events/6553 END:VEVENT END:VCALENDAR