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DTSTART;TZID=Europe/Madrid:20250206T123000
DTEND;TZID=Europe/Madrid:20250206T143000
DTSTAMP:20260501T061953
CREATED:20250130T124214Z
LAST-MODIFIED:20250130T124214Z
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SUMMARY:BIFI TALK: Giovanni Catania. UCM\, Madrid
DESCRIPTION:Title:Challenges and advances in the training of Energy-Based Models: theoretical insights on non-equilibrium sampling and overfitting \nAbstract \nIn the context of unsupervised learning and generative models in artificial intelligence\, energy-based models (EBMs) provide a simple way to describe arbitrary complex datasets\, by encoding their empirical distribution into a Boltzmann probability law with a given energy function. EBMs can be used to generate new data statistically equivalent to the training set\, and to extract microscopic information\, i.e. effective interactions among data components. In this talk\, I will review the basic foundations of EBMs from a statistical physics point of view\, highlighting their connection with maximum-entropy models. I will then focus on typical challenges/issues related to the training\, which is usually performed through an iterative maximum-likelihood procedure. The first problem is related to the sampling protocol\, which is required to estimate one of the terms appearing in the log-likelihood’s gradient: in this context\, I will discuss a recent work that theoretically describes recent proposed training strategies based on non-persistent short Markov Chain MonteCarlo (MCMC) runs as an efficient way to generate good-quality samples. The second part focuses on the impact of finite amount of data in the model’s reconstruction\, a problem related to the concept of overfitting in machine learning: I will discuss recent theoretical results that analyze the training dynamics of simple EBMs (focusing on the Gaussian model)\, and show how i) overfitting emerges from an interplay of different learning timescales associated to different principal components of the data and ii) how different data-correction protocols can be used to mitigate the impact of overfitting for EBMs that employ low-order sufficient statistics of the data. \n  \nThursday\, 6 February 2025\, 12:30 h\nConference Room. Edificio I+D \n 
URL:https://bifi.es/es/schedule/bifi-talk-giovanni-catania-ucm-madrid/
LOCATION:Edificio Institutos I+D\, Mariano Esquillor\, 50018 Zaragoza\, Zaragoza\, Zaragoza\, 50018\, España
CATEGORIES:Eventos
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DTSTART;TZID=Europe/Madrid:20250211T123000
DTEND;TZID=Europe/Madrid:20250211T143000
DTSTAMP:20260501T061953
CREATED:20250210T092951Z
LAST-MODIFIED:20250210T092951Z
UID:8498-1739277000-1739284200@bifi.es
SUMMARY:BIFI-TALK: James Krieger. CNB-CSIC\, Madrid
DESCRIPTION:BIFI-TALK: James Krieger. CNB-CSIC\, Madrid \nTitle: A Perspective on CryoEM\, Heterogeneity and Dynamics \nAbstract \nProteins are dynamic objects that change their shape (conformation) and move around and interact with other molecules (composition) to carry out functions. Cryogenic electron microscopy (CryoEM) is a valuable technique for capturing the resulting heterogeneity\, thanks to many developments in hardware and software. \nNevertheless\, understanding dynamics and function from CryoEM is still a challenge. The last few years has seen a second revolution in image processing to handle heterogeneity in new ways\, driven by developments in machine learning.Many new approaches have been tried\, giving the field much to think about. \nI will reflect on the challenges of analysing CryoEM images and the successes and limitations achieved with new heterogeneity methods\, focusing on two methods developed in our lab: Zernike3D and HetSIREN. \nI will give examples based on synthetic data\, widely used public data sets and specific systems that we have studied\, particularly the coronavirus Spike protein. \nThursday\, 11 February 2025\, 12:30 h\nConference Room. Edificio I+D \n 
URL:https://bifi.es/es/schedule/bifi-talk-james-krieger-cnb-csic-madrid/
LOCATION:Edificio Institutos I+D\, Mariano Esquillor\, 50018 Zaragoza\, Zaragoza\, Zaragoza\, 50018\, España
CATEGORIES:Eventos
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DTSTART;TZID=Europe/Madrid:20250221T123000
DTEND;TZID=Europe/Madrid:20250221T143000
DTSTAMP:20260501T061953
CREATED:20250210T093342Z
LAST-MODIFIED:20250210T093431Z
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SUMMARY:BIFI TALK: Angel Perez Lara\, Universidad de Granada
DESCRIPTION:BIFI TALK: Ángel Pérez Lara\, Universidad de Granada \nTitle: Molecular mechanism of neurotransmitter release machinery \nAbstract \nTransmission of information between neurons relies on the neurotransmitter release from synaptic vesicles into the synaptic cleft upon the influx of Ca2+\, a process known as synaptic exocytosis. Synaptic exocytosis is mediated by the SNARE proteins syntaxin 1 (syx-1A)\, synaptobrevin-2 (syb-2)\, and SNAP-25\, which form the core of the supramolecular fusion machinery. However\, SNARE proteins require additional regulatory proteins to control the early steps of their assembly\, such as Munc-18 and Munc-13\, and proteins that are specialized for fast\, calcium-dependent synaptic exocytosis\, such as synaptotagmin and complexin. Additionally\, after exocytosis\, the SNARE complex needs to be disassembled by the NSF/a-SNAP complex to recycle the individual SNARE proteins for another round of neurotransmitter release. \nUnderstanding the molecular mechanisms underlying synaptic vesicle exocytosis and recycling is a central goal of molecular neuroscience. Despite major efforts by many laboratories\, we have still no coherent picture of the sequence of the protein associations and dissociations\, and the related conformational changes. Our lab aims to characterize the sequence of protein associations and dissociations of the assembly and disassembly of the SNARE complex -the choreography-\, and its regulation\, providing an in-depth understanding of the synaptic vesicle exocytosis. \nFriday\, 21 February 2025\, 12:30 h\nConference Room. Edificio I+D
URL:https://bifi.es/es/schedule/bifi-talk-angel-perez-lara-universidad-de-granada/
LOCATION:Edificio Institutos I+D\, Mariano Esquillor\, 50018 Zaragoza\, Zaragoza\, Zaragoza\, 50018\, España
CATEGORIES:Eventos
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