Mathematical model which describes the time dependence of a point in a geometrical space
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Upskilling instead of conditioning - coaching expert Marianne Davies shares her dynamic approach to coaching and training that has coaches, riders AND horses wanting more Marianne Davies is an expert in coaching riders and developing equestrian coaches. She is a senior coaching developer for UK Coaching and runs her own coaching business, Dynamics Coaching and in her spare time she is completing a PhD and leading ground breaking research in coaching science. This week she shares her dynamic approach to coaching that sees both the horse and rider as active participants in the learning process, which is quite different from behaviourist approaches, such as those used in equitation science. Marianne explains the science behind her approach, and in the second half of the episode she gives some really practical advice for riders and explains how to set up training situations to help your horse learn. It's a great conversation, we hope you enjoy it! Terminology Affordance - opportunity to do something that a horse or person perceives - when coaching and training our horses, we can change the environment to make it easier for the horse (or the rider) to recognise an opportunity so they can attempt a desirable movement or posture. Constraints-led approach to learning - introductory article https://adaptivemovement.net/blog/brief-introduction-to-the-constraints-led-approach/ Papers mentioned in the podcast Wulf & Lethwaite (2016) Optimizing performance through intrinsic motivation and attention for learning: The OPTIMAL theory of motor learning https://pubmed.ncbi.nlm.nih.gov/26833314/ Scott Kelso (1995) Dynamical system theory and human movement and learning. https://scholar.google.com/citations?user=-VlkX4YAAAAJ
Outline00:00 - Intro00:58 - Early steps… in physics!05:17 - AI in Edinburgh08:00 - Connectionism10:37 - Robot learning19:02 - Imitation learning23:00 - On pursuing a PhD24:45 - Californian chronicles30:10 - Modularity33:20 - Challenges in robot learning39:44 - Dexterous manipulation43:52 - Dynamical systems47:37 - Combining ML and control51:25 - Human-robot interaction54:24 - Safety and compliance57:54 - Deadlines for papers1:06:38 - Advice to future students1:07:08 - OutroLinksAude's lab: http://tinyurl.com/4nsx2kraRobot learning: http://tinyurl.com/2ty25t2rConnectionism: http://tinyurl.com/mrd76zfxI. Demiris: http://tinyurl.com/nhhn6ymuHebbian learning: http://tinyurl.com/35ey7um5DRAMA (paper): http://tinyurl.com/4fvbs867Imitation learning: http://tinyurl.com/2af3aew4Mirror neurons: http://tinyurl.com/4nd3sm75G. Rizzolatti: http://tinyurl.com/5b4xfab5Embodied cognition: http://tinyurl.com/5284kp8fA biologically inspired robotic model for learning by imitation: http://tinyurl.com/4j33nphvM. Airbib: http://tinyurl.com/3bu3y5dzRecent Advances in Robot Learning from Demonstration: http://tinyurl.com/487pm3xkSynthetic brain imaging (paper): http://tinyurl.com/38uerwk7Catching Objects in Flight (paper): http://tinyurl.com/38d8fk9mFeasibility not optimality (video): http://tinyurl.com/mwa8b7etLearning multiple-attractors (paper): http://tinyurl.com/2j3yxwm8On human compliance (paper): http://tinyurl.com/4vp2kmhwDeadlines for conferences: http://tinyurl.com/mpwntktySupport the showPodcast infoPodcast website: https://www.incontrolpodcast.com/Apple Podcasts: https://tinyurl.com/5n84j85jSpotify: https://tinyurl.com/4rwztj3cRSS: https://tinyurl.com/yc2fcv4yYoutube: https://tinyurl.com/bdbvhsj6Facebook: https://tinyurl.com/3z24yr43Twitter: https://twitter.com/IncontrolPInstagram: https://tinyurl.com/35cu4kr4Acknowledgments and sponsorsThis episode was supported by the National Centre of Competence in Research on «Dependable, ubiquitous automation» and the IFAC Activity fund. The podcast benefits from the help of an incredibly talented and passionate team. Special thanks to L. Seward, E. Cahard, F. Banis, F. Dörfler, J. Lygeros, ETH studio and mirrorlake . Music was composed by A New Element.
Recorded on Aug 29, 2023 in München, Germany. Video version available on YouTube.Can we meaningfully talk about causality in dynamical systems?Some people are puzzled when it comes to dynamical systems and the idea of causation.Dynamical systems well-known in physics, social sciences, and biology are often thought of as a special family of systems, where it might be difficult to meaningfully talk about causal direction. Naftali Weinberger devoted his career to examining the relationships between system dynamics, causality and the phenomena known broadly as "complexity". We explore what does "intervention" mean in a dynamical system and we deconstruct common intuitions about causality and system's equilibrium. We discuss the importance of time scales when defining a causal system, analyze what could have inspired Bertrand Russell to say that causality is a "relic of a bygone age" and ponder the phenomenon of emergence. Finally, Naftali shares his advice for those of us just starting exploring the uncharted territory of causal inference and discovery. Warning: this conversation might bend your sense of reality. Use with caution! Ready to dive in? About The GuestNaftali Weinberger, PhD is a Researcher at Munich Center for Mathematical Philosophy at LMU. His research is focused on causality, dynamical systems and fairness. He works with scientists, researchers and philosophers around the globe helping them address challenges in diverse fields like climate change, psychometrics, fairness and more. Connect with Naftali: Naftali on Twitter/XNaftali on BlueSky Naftali's web pageAbout The HostAleksander (Alex) Molak is an independent machine learning researcher, educator, entrepreneur and a best-selling author in the area of causality.Connect with Alex:Alex on the InternetLinks are available hereCausal Bandits TeamProject Coordinator: Taiba MalikVideo and Audio Editing: Navneet SharmCausal Bandits PodcastCausal AI || Causal Machine Learning || Causal Inference & DiscoveryWeb: https://causalbanditspodcast.comConnect on LinkedIn: https://www.linkedin.com/in/aleksandermolak/Join Causal Python Weekly: https://causalpython.io The Causal Book: https://amzn.to/3QhsRz4
Support the show to get full episodes and join the Discord community. Check out my free video series about what's missing in AI and Neuroscience Eric Shea-Brown is a theoretical neuroscientist and principle investigator of the working group on neural dynamics at the University of Washington. In this episode, we talk a lot about dynamics and dimensionality in neural networks... how to think about them, why they matter, how Eric's perspectives have changed through his career. We discuss a handful of his specific research findings about dynamics and dimensionality, like how dimensionality changes when one is performing a task versus when you're just sort of going about your day, what we can say about dynamics just by looking at different structural connection motifs, how different modes of learning can rely on different dimensionalities, and more.We also talk about how he goes about choosing what to work on and how to work on it. You'll hear in our discussion how much credit Eric gives to those surrounding him and those who came before him - he drops tons of references and names, so get ready if you want to follow up on some of the many lines of research he mentions. Eric's website. Related papers Predictive learning as a network mechanism for extracting low-dimensional latent space representations. A scale-dependent measure of system dimensionality. From lazy to rich to exclusive task representations in neural networks and neural codes. Feedback through graph motifs relates structure and function in complex networks. 0:00 - Intro 4:15 - Reflecting on the rise of dynamical systems in neuroscience 11:15 - DST view on macro scale 15:56 - Intuitions 22:07 - Eric's approach 31:13 - Are brains more or less impressive to you now? 38:45 - Why is dimensionality important? 50:03 - High-D in Low-D 54:14 - Dynamical motifs 1:14:56 - Theory for its own sake 1:18:43 - Rich vs. lazy learning 1:22:58 - Latent variables 1:26:58 - What assumptions give you most pause?
SSOF App & Community: https://sweetscienceoffighting.com/ssof-underground/ SSOF Rash Guard & Shorts Discount - Code "SWEETSCIENCE"https://sweetscienceoffighting.com/sweet-science-rash-guard Iron Neck - Code "SSOF10" https://sweetscienceoffighting.com/ironneck Craig Twentyman has a wealth of experience working within rugby having spent 12 years at Rugby Australia with their 7s and 15s teams. He then moved to rugby league with the NZ Warriors and now heads the NZ Black Ferns Women's rugby team as their strength & conditioning coach. Timestamps 0:00 Craig's background 5:00 Getting bigger without losing speed and power 10:00 Dynamical systems theory concepts to maintain speed 23:10 Training week structure for building muscle as an athlete 27:05 Building muscle when competing often 28:44 Training splits 30:30 Craig's favorite power exercises 32:40 Muscle slack theory 35:10 How strong is strong enough 44:00 Conditioning transfer to sport Craig's Instagram: https://www.instagram.com/craigtwentyman LinkedIn: https://www.linkedin.com/in/craig-twentyman-66397833 ★ ★ FREE Stuff! ★ ★ For The Strikers - 5 Powerful Tips For Developing Devastating KO Power! https://sweetscienceoffighting.com/devastating-ko-power-yt/ For The Grapplers - 9 Tricks To Build Specific BJJ Strength Without The Rampant Steroid Abuse! https://sweetscienceoffighting.com/7-awesome-ways-to-get-stronger-for-grappling-bjj/ For The MMA Athlete - 6 Secrets From The Pros To Never Gas Out https://sweetscienceoffighting.com/6-secrets-from-the-pros-to-never-gas-out/ Online Training Programs:
------------------Support the channel------------ Patreon: https://www.patreon.com/thedissenter PayPal: paypal.me/thedissenter PayPal Subscription 3 Dollars: https://tinyurl.com/ybn6bg9l PayPal Subscription 5 Dollars: https://tinyurl.com/ycmr9gpz PayPal Subscription 10 Dollars: https://tinyurl.com/y9r3fc9m This show is sponsored by Enlites, Learning & Development done differently. Check the website here: http://enlites.com/ Dr. Inês Hipólito is a faculty member at Macquarie University, where she serves as a Lecturer of Philosophy of AI and a researcher at the Ethics and Agency Research Center. Furthermore, she holds the position of Ethicist of AI at Verses, a pioneering cognitive computing company specializing in next-generation AI, with Karl Friston serving as Chief Research bridging the gap between academia and industry, contributing to ethical considerations embedded within cutting-edge AI advancements. As a co-founder and vice-president of the International Society of the Philosophy of the Sciences of the Mind, she is a passionate advocate for diversity and inclusivity in the field, serving as an elected member of the Women in Philosophy Committee and the Committee in Diversity and Inclusivity at the Australasian Association of Philosophy. In this episode, we talk about dynamical approaches in cognitive science. We start by discussing the differences between computational-representational approaches and dynamical approaches in cognitive science. We talk about 4E cognition. We then get into a recent paper by Dr. Hipólito, Mind as Motion, and talk about a shift in psychology towards dynamical approaches, and the role of the sociocultural context. We discuss if psychological experiences have any intrinsic value, and if science is independent of any sociocultural context. Finally, we discuss if AI systems can become human-like if they are not embodied. -- A HUGE THANK YOU TO MY PATRONS/SUPPORTERS: PER HELGE LARSEN, JERRY MULLER, HANS FREDRIK SUNDE, BERNARDO SEIXAS, OLAF ALEX, ADAM KESSEL, MATTHEW WHITINGBIRD, ARNAUD WOLFF, TIM HOLLOSY, HENRIK AHLENIUS, JOHN CONNORS, FILIP FORS CONNOLLY, DAN DEMETRIOU, ROBERT WINDHAGER, RUI INACIO, ZOOP, MARCO NEVES, COLIN HOLBROOK, SIMON COLUMBUS, PHIL KAVANAGH, MIKKEL STORMYR, SAMUEL ANDREEFF, FRANCIS FORDE, TIAGO NUNES, FERGAL CUSSEN, HAL HERZOG, NUNO MACHADO, JONATHAN LEIBRANT, JOÃO LINHARES, STANTON T, SAMUEL CORREA, ERIK HAINES, MARK SMITH, JOÃO EIRA, TOM HUMMEL, SARDUS FRANCE, DAVID SLOAN WILSON, YACILA DEZA-ARAUJO, ROMAIN ROCH, DIEGO LONDOÑO CORREA, YANICK PUNTER, ADANER USMANI, CHARLOTTE BLEASE, NICOLE BARBARO, ADAM HUNT, PAWEL OSTASZEWSKI, NELLEKE BAK, GUY MADISON, GARY G HELLMANN, SAIMA AFZAL, ADRIAN JAEGGI, PAULO TOLENTINO, JOÃO BARBOSA, JULIAN PRICE, EDWARD HALL, HEDIN BRØNNER, DOUGLAS FRY, FRANCA BORTOLOTTI, GABRIEL PONS CORTÈS, URSULA LITZCKE, SCOTT, ZACHARY FISH, TIM DUFFY, SUNNY SMITH, JON WISMAN, DANIEL FRIEDMAN, WILLIAM BUCKNER, PAUL-GEORGE ARNAUD, LUKE GLOWACKI, GEORGIOS THEOPHANOUS, CHRIS WILLIAMSON, PETER WOLOSZYN, DAVID WILLIAMS, DIOGO COSTA, ANTON ERIKSSON, CHARLES MOREY, ALEX CHAU, AMAURI MARTÍNEZ, CORALIE CHEVALLIER, BANGALORE ATHEISTS, LARRY D. LEE JR., OLD HERRINGBONE, STARRY, MICHAEL BAILEY, DAN SPERBER, ROBERT GRESSIS, IGOR N, JEFF MCMAHAN, JAKE ZUEHL, BARNABAS RADICS, MARK CAMPBELL, TOMAS DAUBNER, LUKE NISSEN, CHRIS STORY, KIMBERLY JOHNSON, BENJAMIN GELBART, JESSICA NOWICKI, LINDA BRANDIN, NIKLAS CARLSSON, ISMAËL BENSLIMANE, GEORGE CHORIATIS, VALENTIN STEINMANN, PER KRAULIS, KATE VON GOELER, ALEXANDER HUBBARD, LIAM DUNAWAY, BR, MASOUD ALIMOHAMMADI, PURPENDICULAR, JONAS HERTNER, AND GREGORY HASTINGS! A SPECIAL THANKS TO MY PRODUCERS, YZAR WEHBE, JIM FRANK, ŁUKASZ STAFINIAK, TOM VANEGDOM, BERNARD HUGUENEY, CURTIS DIXON, BENEDIKT MUELLER, THOMAS TRUMBLE, KATHRINE AND PATRICK TOBIN, JONCARLO MONTENEGRO, AL NICK ORTIZ, NICK GOLDEN, AND ROSEY! AND TO MY EXECUTIVE PRODUCERS, MATTHEW LAVENDER, SERGIU CODREANU, AND BOGDAN KANIVETS!
في الحلقة 90 لـ #بودكاست
Dr Rob outlines three aspects of genetics that tell us that, scientifically, the human species is doomed to eventual extinction. These include the rate of mutation accumulation in our population over time, the inability of natural selection to remove most of those mutations, and the sheer number of children that would be required to remove the mutations, given perfect selection. These all argue that there is no hope, collectively, in any evolutionary process. Thus, biblically, the only hope for us individually is through belief in Jesus. Links: Genetic entropy Basener et al. 2023 Dynamical systems and fitness maximization in evolutionary biology Fisher's failure and the dramatic end of neo-Darwinism Genealogy vs Phylogeny: The War Continues
Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.07.15.549166v1?rss=1 Authors: Boute, J., Destexhe, A. Abstract: In the awake brain, cerebral cortex displays asynchronous-irregular (AI) states, where neurons fire irregularly and with low correlation. Neural networks can display AI states that are self-sustained through recurrent connections, or in some cases, need an external input to sustain activity. In this paper, we aim at comparing these two dynamics and their consequences on responsiveness. We first show that the first Lyapunov exponent (FLE) can differ between self-sustained and driven networks, the former displaying a higher FLE than the late. Next, we show that this impact the dynamics of the system, leading to a tendency for self-sustained networks to be more responsive, both properties that can also be captured by mean-field models. We conclude that there is a dynamical and excitability difference between the two types of networks besides their apparent similar collective firing. The model predicts that calculating FLE from population activities in experimental data could provide a way to identify if real neural networks are self-sustained or driven. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC
We introduce a new class of time-continuous recurrent neural network models. Instead of declaring a learning system's dynamics by implicit nonlinearities, we construct networks of linear first-order dynamical systems modulated via nonlinear interlinked gates. The resulting models represent dynamical systems with varying (i.e., liquid) time-constants coupled to their hidden state, with outputs being computed by numerical differential equation solvers. These neural networks exhibit stable and bounded behavior, yield superior expressivity within the family of neural ordinary differential equations, and give rise to improved performance on time-series prediction tasks. To demonstrate these properties, we first take a theoretical approach to find bounds over their dynamics, and compute their expressive power by the trajectory length measure in a latent trajectory space. We then conduct a series of time-series prediction experiments to manifest the approximation capability of Liquid Time-Constant Networks (LTCs) compared to classical and modern RNNs. 2020: Ramin M. Hasani, Mathias Lechner, Alexander Amini, D. Rus, R. Grosu Recurrent neural network, Time series, Dynamical system, Nonlinear system, Approximation, Experiment, Numerical analysis, Artificial neural network https://arxiv.org/pdf/2006.04439v3.pdf
Welcome to The Nonlinear Library, where we use Text-to-Speech software to convert the best writing from the Rationalist and EA communities into audio. This is: Apparently, of the 195 Million the DoD allocated in University Research Funding Awards in 2022, more than half of them concerned AI or compute hardware research, published by mako yass on July 7, 2023 on LessWrong. Suggests some really interesting focus, so I thought I should mention it. The awards concerned "pursuing basic research spanning multiple scientific disciplines", which makes it pretty interesting that three fifths of them are either directly AI and compute hardware research, or have applications to compute hardware research. From a merit-based review of approximately 340 proposals received, a panel of experts narrowed the proposals to a subset, from which the 28 final awards were selected (Only 26 were listed in the table. I wonder if the other two were a strategic omission.) Take a look at the table of project topics. Bold means probably directly AI/compute, italic means probably primarily applicable to AI/compute. Social Network-Transcendent Behavioral Dynamics Learning Dynamics and Detecting Causal Pathways in Coupled Online- Offline Systems Microelectronic Test Science Exploiting Latent Energy and Electromagnetic Radiation Comprehensive Minimally/non- invasive Multifaceted Assessment of Nano-/ microelectronic Devices (CoMMAND) Cavity Molecular Polaritons MURI: Polariton Chemistry Effects of Radiation Damage on Performance of Wide-Bandgap Electronics REDESIGN: Radiation Effects preDiction through Experimentally validated Simulation of Gallium Nitride Understanding Neural Systems Integration for Competent Autonomy in Decision and Control FLAP: Fast, Lexicographic Agile Integrates Decision and Control in a Spike-Resolved, Sensorimotor Program Nonlinear Optical Material Design with Extreme Interband Nonlinearities Atomic-scale Manipulations of Interband Optical Nonlinearities - (AtoMs➝IONs) Synthetic Quantum Matter Reimagining Atoms and Photons in SYnthetic, DYnamical, and INteracting Quantum matter Composability of Synthetic Biological Circuits Rules of Composition in Synthetic Biology Across Scales of Complexity: Theory and Tools Bio-architected Responsive Materials with 3D Nanoscale Order 3D Nanomaterial Architectures with Programmable Reconfiguration States and Functions Topological Seeds of Complex Response in Materials Programming Multistable Origami and Kirigami Structures via Topological Design Connectivity and Transport in Disordered Hyperuniform Networks Transport in Disordered Hyperuniform Systems and Networks Uncovering the Underlying Neurobiological Mechanisms of Cognitive Fatigue Understanding and Predicting Cognitive Fatigue across Multiple Timescales, Distinct Aspects of Cognition, and Different Individuals with Multiscale Whole Cortex Models Gut-Neuronal Signaling Through Polymeric Mucin via Chemical Probes and Imaging Mucin-mimetic Interventions to Modulate the Gut-Brain Axis ELECTROBIOLOGY: Electronic Control of Biological Communication Faster, More Efficient, and Hybrid Computation in Microbial Bioelectronic Systems ARO Rice University Novel Routes to Majorana Qubits for Topologically- Protected Quantum Information Epitaxial phase-biased Josephson junctions Molecular Doping of Organic Electronic Materials Next Generation Molecular Dopants for Organic Electronics: From Fundamentals to New Device Concepts Learning from Hearing Neurobehavioral, Physiological, and Computational Processes of Auditory Object Learning in Mammals Hydrodynamics of Fish Schooling Revealing the Hydrodynamic Principles of Three-dimensional Fish Schools; From Biology to Schooling Robotics Self-learning for Real-world Perception Intentional multi-modal self-learning to perceive and understand the real world Fundamental Non-equilibrium Processes in Weakly Ionized Hypersonic Flows Development of Validated Hypersonic Plasma Kinetics Models Including Atomic Excitation I...
Link to original articleWelcome to The Nonlinear Library, where we use Text-to-Speech software to convert the best writing from the Rationalist and EA communities into audio. This is: Apparently, of the 195 Million the DoD allocated in University Research Funding Awards in 2022, more than half of them concerned AI or compute hardware research, published by mako yass on July 7, 2023 on LessWrong. Suggests some really interesting focus, so I thought I should mention it. The awards concerned "pursuing basic research spanning multiple scientific disciplines", which makes it pretty interesting that three fifths of them are either directly AI and compute hardware research, or have applications to compute hardware research. From a merit-based review of approximately 340 proposals received, a panel of experts narrowed the proposals to a subset, from which the 28 final awards were selected (Only 26 were listed in the table. I wonder if the other two were a strategic omission.) Take a look at the table of project topics. Bold means probably directly AI/compute, italic means probably primarily applicable to AI/compute. Social Network-Transcendent Behavioral Dynamics Learning Dynamics and Detecting Causal Pathways in Coupled Online- Offline Systems Microelectronic Test Science Exploiting Latent Energy and Electromagnetic Radiation Comprehensive Minimally/non- invasive Multifaceted Assessment of Nano-/ microelectronic Devices (CoMMAND) Cavity Molecular Polaritons MURI: Polariton Chemistry Effects of Radiation Damage on Performance of Wide-Bandgap Electronics REDESIGN: Radiation Effects preDiction through Experimentally validated Simulation of Gallium Nitride Understanding Neural Systems Integration for Competent Autonomy in Decision and Control FLAP: Fast, Lexicographic Agile Integrates Decision and Control in a Spike-Resolved, Sensorimotor Program Nonlinear Optical Material Design with Extreme Interband Nonlinearities Atomic-scale Manipulations of Interband Optical Nonlinearities - (AtoMs➝IONs) Synthetic Quantum Matter Reimagining Atoms and Photons in SYnthetic, DYnamical, and INteracting Quantum matter Composability of Synthetic Biological Circuits Rules of Composition in Synthetic Biology Across Scales of Complexity: Theory and Tools Bio-architected Responsive Materials with 3D Nanoscale Order 3D Nanomaterial Architectures with Programmable Reconfiguration States and Functions Topological Seeds of Complex Response in Materials Programming Multistable Origami and Kirigami Structures via Topological Design Connectivity and Transport in Disordered Hyperuniform Networks Transport in Disordered Hyperuniform Systems and Networks Uncovering the Underlying Neurobiological Mechanisms of Cognitive Fatigue Understanding and Predicting Cognitive Fatigue across Multiple Timescales, Distinct Aspects of Cognition, and Different Individuals with Multiscale Whole Cortex Models Gut-Neuronal Signaling Through Polymeric Mucin via Chemical Probes and Imaging Mucin-mimetic Interventions to Modulate the Gut-Brain Axis ELECTROBIOLOGY: Electronic Control of Biological Communication Faster, More Efficient, and Hybrid Computation in Microbial Bioelectronic Systems ARO Rice University Novel Routes to Majorana Qubits for Topologically- Protected Quantum Information Epitaxial phase-biased Josephson junctions Molecular Doping of Organic Electronic Materials Next Generation Molecular Dopants for Organic Electronics: From Fundamentals to New Device Concepts Learning from Hearing Neurobehavioral, Physiological, and Computational Processes of Auditory Object Learning in Mammals Hydrodynamics of Fish Schooling Revealing the Hydrodynamic Principles of Three-dimensional Fish Schools; From Biology to Schooling Robotics Self-learning for Real-world Perception Intentional multi-modal self-learning to perceive and understand the real world Fundamental Non-equilibrium Processes in Weakly Ionized Hypersonic Flows Development of Validated Hypersonic Plasma Kinetics Models Including Atomic Excitation I...
Hello Interactors,We're now into summer, but I wanted to sneak in one last cartography post. It's a leap from last week's post into the field of human dynamics. If you don't want to read the whole thing (shame on you
Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.04.09.536154v1?rss=1 Authors: Jajcay, N., Hlinka, J. Abstract: One of the interesting aspects of EEG data is the presence of temporally stable and spatially coherent patterns of activity, known as microstates, which have been linked to various cognitive and clinical phenomena. However, there is still no general agreement on the interpretation of microstate analysis. Various clustering algorithms have been used for microstate computation, and multiple studies suggest that the microstate time series may provide insight into the neural activity of the brain in the resting state. This study addresses two gaps in the literature. Firstly, by applying several state-of-the-art microstate algorithms to a large dataset of EEG recordings, we aim to characterise and describe various microstate algorithms. We demonstrate and discuss why the three "classically" used algorithms ((T)AAHC and modified K-Means) yield virtually the same results, while HMM algorithm generates the most dissimilar results. Secondly, we aim to test the hypothesis that dynamical microstate properties might be, to a large extent, determined by the linear characteristics of the underlying EEG signal, in particular, by the cross-covariance and autocorrelation structure of the EEG data. To this end, we generated a Fourier transform surrogate of the EEG signal to compare microstate properties. Here, we found that these are largely similar, thus hinting that microstate properties depend to a very high degree on the linear covariance and autocorrelation structure of the underlying EEG data. Finally, we treated the EEG data as a vector autoregression process, estimated its parameters, and generated surrogate stationary and linear data from fitted VAR. We observed that such a linear model generates microstates highly comparable to those estimated from real EEG data, supporting the conclusion that a linear EEG model can help with the methodological and clinical interpretation of both static and dynamic human brain microstate properties. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC
Books in the Video: Series Playlist: https://www.youtube.com/playlist?list... Facebook: https://www.facebook.com/Vervaeke.John/ Twitter: https://twitter.com/vervaeke_john Thirty-first episode of Dr. John Vervaeke's Awakening from the Meaning Crisis.
Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.03.24.534142v1?rss=1 Authors: Vardalakis, N., Aussel, A., Rougier, N. P., Wagner, F. B. Abstract: Neurostimulation of the hippocampal formation has shown promising results for modulating memory but the underlying mechanisms remain unclear. In particular, the effects on hippocampal theta-nested gamma oscillations and theta phase reset, which are both crucial for memory processes, are unknown. Moreover, these effects cannot be investigated using current computational models, which consider theta oscillations with a fixed amplitude and phase velocity. Here, we developed a novel computational model that includes the medial septum, represented as a set of abstract Kuramoto oscillators producing a dynamical theta rhythm with phase reset, and the hippocampal formation, composed of biophysically-realistic neurons and able to generate theta-nested gamma oscillations under theta drive. We showed that this system can exhibit bistability in a specific range of parameters and that a single stimulation pulse could switch the network behavior from non-oscillatory to a state producing theta-nested gamma oscillations. Next, we demonstrated that for a theta input too weak to generate theta-nested gamma oscillations, pulse train stimulation at the theta frequency could restore seemingly physiological oscillations. Importantly, the presence of phase reset influenced whether these two effects depended on the phase at which stimulation onset was delivered, which has practical implications for designing neurostimulation protocols that are triggered by the phase of ongoing theta oscillations. This novel model opens new avenues for studying the effects of neurostimulation on the hippocampal formation. Furthermore, our hybrid approach that combines different levels of abstraction could be extended in future work to other neural circuits that produce dynamical brain rhythms. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC
Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.03.13.532479v1?rss=1 Authors: Abbaspourazad, H., Erturk, E., Pesaran, B., Shanechi, M. M. Abstract: Inferring complex spatiotemporal dynamics in neural population activity is critical for investigating neural mechanisms and developing neurotechnology. These activity patterns are noisy observations of lower-dimensional latent factors and their nonlinear dynamical structure. A major unaddressed challenge is to model this nonlinear structure, but in a manner that allows for flexible inference, whether causally, non-causally, or in the presence of missing neural observations. We address this challenge by developing DFINE, a new neural network that separates the model into dynamic and manifold latent factors, such that the dynamics can be modeled in tractable form. We show that DFINE achieves flexible nonlinear inference across diverse behaviors and brain regions. Further, despite enabling flexible inference unlike prior neural network models of population activity, DFINE also better predicts the behavior and neural activity, and better captures the latent neural manifold structure. DFINE can both enhance future neurotechnology and facilitate investigations across diverse domains of neuroscience. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC
Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.02.24.529950v1?rss=1 Authors: Hettinger, Z. R., Hu, S., Mamiya, H., Sahu, A., Iijima, H., Wang, K., Gilmer, G., Miller, A., Nasello, G., D'Amore, A., Vorp, D., Rando, T. A., Xing, J., Ambrosio, F. Abstract: Loss of muscle stem cell (MuSC) self-renewal with aging reflects a combination of influences from the intracellular (e.g., post-transcriptional modifications) and extracellular (e.g., matrix stiffness) environment. Whereas conventional single cell analyses have revealed valuable insights into factors contributing to impaired self-renewal with age, most are limited by static measurements that fail to capture nonlinear dynamics. Using bioengineered matrices mimicking the stiffness of young and old muscle, we showed that while young MuSCs were unaffected by aged matrices, old MuSCs were phenotypically rejuvenated by young matrices. Dynamical modeling of RNA velocity vector fields in silico revealed that soft matrices promoted a self-renewing state in old MuSCs by attenuating RNA decay. Vector field perturbations demonstrated that the effects of matrix stiffness on MuSC self-renewal could be circumvented by fine-tuning the expression of the RNA decay machinery. These results demonstrate that post-transcriptional dynamics dictate the negative effect of aged matrices on MuSC self-renewal. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC
Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2023.01.12.523643v1?rss=1 Authors: Ebert, S., Buffet, T., Sermet, B. S., Marre, O., Cessac, B. Abstract: A fundamental task for the brain is to generate predictions of future sensory inputs, and signal errors in these predictions. Many neurons have been shown to signal omitted stimuli during periodic stimulation, even in the retina. However, the mechanisms of this error signaling are unclear. Here we show that depressing inhibitory synapses enable the retina to signal an omitted stimulus in a flash sequence. While ganglion cells, the retinal output, responded to an omitted flash with a constant latency over many frequencies of the flash sequence, we found that this was not the case once inhibition was blocked. We built a simple circuit model and showed that depressing inhibitory synapses were a necessary component to reproduce our experimental findings. We also generated new predictions with this model, that we confirmed experimentally. Depressing inhibitory synapses could thus be a key component to generate the predictive responses observed in many brain areas. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC
Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2022.12.16.520768v1?rss=1 Authors: O'Shea, D. J., Duncker, L., Goo, W., Sun, X., Vyas, S., Trautmann, E. M., Diester, I., Ramakrishnan, C., Deisseroth, K., Sahani, M., Shenoy, K. V. Abstract: The rich repertoire of skilled mammalian behavior is the product of neural circuits that generate robust and flexible patterns of activity distributed across populations of neurons. Decades of associative studies have linked many behaviors to specific patterns of population activity, but association alone cannot reveal the dynamical mechanisms that shape those patterns. Are local neural circuits high- dimensional dynamical reservoirs able to generate arbitrary superpositions of patterns with appropriate excitation? Or might circuit dynamics be shaped in response to behavioral context so as to generate only the low-dimensional patterns needed for the task at hand? Here, we address these questions within primate motor cortex by delivering optogenetic and electrical microstimulation perturbations during reaching behavior. We develop a novel analytic approach that relates measured activity to theoretically tractable, dynamical models of excitatory and inhibitory neurons. This computational model captures the dynamical effects of these perturbations and demonstrates that motor cortical activity during reaching is shaped by a self-contained, low-dimensional dynamical system. The subspace containing task-relevant dynamics proves to be oriented so as to be robust to strong non-normal amplification within cortical circuits. This task dynamics space exhibits a privileged causal relationship with behavior, in that stimulation in motor cortex perturb reach kinematics only to the extent that it alters neural states within this subspace. Our results resolve long-standing questions about the dynamical structure of cortical activity associated with movement, and illuminate the dynamical perturbation experiments needed to understand how neural circuits throughout the brain generate complex behavior. Copy rights belong to original authors. Visit the link for more info Podcast created by Paper Player, LLC
On the sociology and hierarchy of voids: a study of seven CAVITY nearby galaxy voids and their dynamical CosmicFlows-3 environment by H. M. Courtois et al. on Wednesday 30 November Context. The present study addresses a key question for our understanding of the relation between void galaxies and their environment: the relationship between luminous and dark matter in and around voids. Aims. To explore how empty of matter local Universe voids are, we study the full (dark+luminous) matter content of seven nearby cosmic voids that are fully contained within the CosmicFlows-3 volume. Methods. The cosmic voids matter density profiles are independently obtained using two different methods. They are built on one hand from the galaxy redshift space 2 points-correlation function and, on the other hand, using peculiar velocity gradients from the CosmicFlows-3 dataset. Results. The results are noticeable since when using the redshift survey, all voids show a radial positive gradient of galaxies, while based on the dynamical analysis, only three of these voids display a clear underdensity of matter in their center. Conclusions. It is the first time such a detailed observational analysis of voids is conducted, showing that void emptiness should be derived from dynamical information. Yet, from this limited study, the Hercules void is the best candidate for a local Universe pure "pristine volume" expanding in 3 directions with no dark matter located in that void. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.16388v1
On the sociology and hierarchy of voids: a study of seven CAVITY nearby galaxy voids and their dynamical CosmicFlows-3 environment by H. M. Courtois et al. on Wednesday 30 November Context. The present study addresses a key question for our understanding of the relation between void galaxies and their environment: the relationship between luminous and dark matter in and around voids. Aims. To explore how empty of matter local Universe voids are, we study the full (dark+luminous) matter content of seven nearby cosmic voids that are fully contained within the CosmicFlows-3 volume. Methods. The cosmic voids matter density profiles are independently obtained using two different methods. They are built on one hand from the galaxy redshift space 2 points-correlation function and, on the other hand, using peculiar velocity gradients from the CosmicFlows-3 dataset. Results. The results are noticeable since when using the redshift survey, all voids show a radial positive gradient of galaxies, while based on the dynamical analysis, only three of these voids display a clear underdensity of matter in their center. Conclusions. It is the first time such a detailed observational analysis of voids is conducted, showing that void emptiness should be derived from dynamical information. Yet, from this limited study, the Hercules void is the best candidate for a local Universe pure "pristine volume" expanding in 3 directions with no dark matter located in that void. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.16388v1
The dynamical state of the globular clusters Rup 106 and IC 4499 by Giacomo Beccari et al. on Wednesday 30 November The dynamical evolution of globular clusters is theoretically described by a series of well known events typical of N-body systems. Still, the identification of observational signatures able to empirically describe the stage of dynamical evolution of a stellar system of the density typical of a globular cluster, represents a challenge. In this paper we study the dynamical age of the globular clusters Rup 106 and IC 4499. To this aim, we study the radial distribution of the Blue Straggler Stars via the A+ parameter and of the slope of the Main Sequence Mass Function. Both tracers show that Rup 106 and IC 4499 are dynamically young clusters where dynamical friction has just started to segregate massive stars towards the clusters' centre. In fact, we observe that the Blue Straggler stars are more centrally concentrated in both clusters than the reference population. On the same line, we find that in both cases the slope of the mass function significantly decreases as a function of the cluster-centric distances. This result provides additional support for the use of the the radial distribution of the blue stragglers as a powerful observationally convenient indicator of the cluster dynamical age. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.12884v2
On the sociology and hierarchy of voids: a study of seven CAVITY nearby galaxy voids and their dynamical CosmicFlows-3 environment by H. M. Courtois et al. on Wednesday 30 November Context. The present study addresses a key question for our understanding of the relation between void galaxies and their environment: the relationship between luminous and dark matter in and around voids. Aims. To explore how empty of matter local Universe voids are, we study the full (dark+luminous) matter content of seven nearby cosmic voids that are fully contained within the CosmicFlows-3 volume. Methods. The cosmic voids matter density profiles are independently obtained using two different methods. They are built on one hand from the galaxy redshift space 2 points-correlation function and, on the other hand, using peculiar velocity gradients from the CosmicFlows-3 dataset. Results. The results are noticeable since when using the redshift survey, all voids show a radial positive gradient of galaxies, while based on the dynamical analysis, only three of these voids display a clear underdensity of matter in their center. Conclusions. It is the first time such a detailed observational analysis of voids is conducted, showing that void emptiness should be derived from dynamical information. Yet, from this limited study, the Hercules void is the best candidate for a local Universe pure "pristine volume" expanding in 3 directions with no dark matter located in that void. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.16388v1
The dynamical state of the globular clusters Rup 106 and IC 4499 by Giacomo Beccari et al. on Wednesday 30 November The dynamical evolution of globular clusters is theoretically described by a series of well known events typical of N-body systems. Still, the identification of observational signatures able to empirically describe the stage of dynamical evolution of a stellar system of the density typical of a globular cluster, represents a challenge. In this paper we study the dynamical age of the globular clusters Rup 106 and IC 4499. To this aim, we study the radial distribution of the Blue Straggler Stars via the A+ parameter and of the slope of the Main Sequence Mass Function. Both tracers show that Rup 106 and IC 4499 are dynamically young clusters where dynamical friction has just started to segregate massive stars towards the clusters' centre. In fact, we observe that the Blue Straggler stars are more centrally concentrated in both clusters than the reference population. On the same line, we find that in both cases the slope of the mass function significantly decreases as a function of the cluster-centric distances. This result provides additional support for the use of the the radial distribution of the blue stragglers as a powerful observationally convenient indicator of the cluster dynamical age. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.12884v2
The dynamical state of the globular clusters Rup 106 and IC 4499 by Giacomo Beccari et al. on Wednesday 30 November The dynamical evolution of globular clusters is theoretically described by a series of well known events typical of N-body systems. Still, the identification of observational signatures able to empirically describe the stage of dynamical evolution of a stellar system of the density typical of a globular cluster, represents a challenge. In this paper we study the dynamical age of the globular clusters Rup 106 and IC 4499. To this aim, we study the radial distribution of the Blue Straggler Stars via the A+ parameter and of the slope of the Main Sequence Mass Function. Both tracers show that Rup 106 and IC 4499 are dynamically young clusters where dynamical friction has just started to segregate massive stars towards the clusters' centre. In fact, we observe that the Blue Straggler stars are more centrally concentrated in both clusters than the reference population. On the same line, we find that in both cases the slope of the mass function significantly decreases as a function of the cluster-centric distances. This result provides additional support for the use of the the radial distribution of the blue stragglers as a powerful observationally convenient indicator of the cluster dynamical age. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.12884v2
Resonant Dynamical Friction: Analytical Description by Yonadav Barry Ginat et al. on Tuesday 29 November We derive an analytical model for the so-called phenomenon of `resonant dynamical friction', where a disc of stars around a super-massive black hole interacts with a massive perturber, so as to align its inclination with the disc's orientation. We show that it stems from singular behaviour of the orbit-averaged equations of motion, which leads to a rapid alignment of the argument of the ascending node $Omega$ of each of the disc stars, with that of the perturber, $Omega_{rm p}$, with a phase-difference of $90^circ$, for all stars whose maximum possible $dot{Omega}$ (maximised over all values of $Omega$ for all the disc stars), is greater than $dot{Omega}_{rm p}$; this corresponds approximately to all stars whose semi-major axes are less than twice that of the perturber. This persists until the perturber enters the disc. The predictions of this model agree with a suite of numerical $N$-body simulations which we perform to explore this phenomenon, for a wide range of initial conditions, masses, emph{etc.}, and are an instance of a general phenomenon. Similar effects could occur in the context of planetary systems, too. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.14784v1
The effect of saturated thermal conduction on clouds in a hot plasma by Bastian Sander et al. on Tuesday 29 November We numerically investigate the internal evolution of multiphase clouds, which are at rest with respect to an ambient, highly ionized medium (HIM) representing the hot component of the circumgalactic medium (CGM). Time-dependent saturated thermal conduction and its implications like condensation rates and mixing efficiency are assessed in multiphase clouds. Our simulations are carried out by using the adaptive mesh refinement code Flash. We perform a grid of models of which we present here those characteristic for the presented study. The model clouds are initially in both hydrostatic and thermal equilibrium and are in pressure balance with the HIM. Thus, they have steep gradients in both temperature and density at the interface to HIM leading to non-negligible thermal conduction. Several physical processes are considered numerically or semi-analytically: thermal conduction, radiative cooling and external heating of gas, self-gravity, mass diffusion, and dissociation of molecules and ionization of atoms. It turns out that saturated thermal conduction triggers a continuous condensation irrespective of cloud mass. Dynamical interactions with ambient HIM all relate to the radial density gradient in the clouds: (1) mass flux due to condensation is the higher the more homogeneous the clouds are; (2) mixing of condensed gas with cloud gas is easier in low-mass clouds, because of their shallower radial density gradient; thus (3) accreted gas is distributed more efficiently. A distinct and sub-structured transition zone forms at the interface between cloud and HIM, which starts at smaller radii and is much narrower as deduced from analytical theory. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.15284v1
Non-thermal emission from mildly relativistic dynamical ejecta of neutron star mergers by Gilad Sadeh et al. on Tuesday 29 November Binary neutron star mergers are expected to produce fast dynamical ejecta, with mildly relativistic velocities extending to $beta=v/c>0.6$. We consider the radio to X-ray synchrotron emission produced by collisionless shocks driven by such fast ejecta into the interstellar medium. Analytic expressions are given for spherical ejecta with broken power-law mass (or energy) distributions, $M(>gammabeta)propto(gammabeta)^{-s}$ with $s=s_{rm KN}$ at $gammabetagamma_0beta_0$ (where $gamma$ is the Lorentz factor). For parameter values characteristic of merger calculation results -- a "shallow" mass distribution, $1
Non-thermal emission from mildly relativistic dynamical ejecta of neutron star mergers by Gilad Sadeh et al. on Monday 28 November Binary neutron star mergers are expected to produce fast dynamical ejecta, with mildly relativistic velocities extending to $beta=v/c>0.6$. We consider the radio to X-ray synchrotron emission produced by collisionless shocks driven by such fast ejecta into the interstellar medium. Analytic expressions are given for spherical ejecta with broken power-law mass (or energy) distributions, $M(>gammabeta)propto(gammabeta)^{-s}$ with $s=s_{rm KN}$ at $gammabetagamma_0beta_0$ (where $gamma$ is the Lorentz factor). For parameter values characteristic of merger calculation results -- a "shallow" mass distribution, $1
Resonant Dynamical Friction: Analytical Description by Yonadav Barry Ginat et al. on Monday 28 November We derive an analytical model for the so-called phenomenon of `resonant dynamical friction', where a disc of stars around a super-massive black hole interacts with a massive perturber, so as to align its inclination with the disc's orientation. We show that it stems from singular behaviour of the orbit-averaged equations of motion, which leads to a rapid alignment of the argument of the ascending node $Omega$ of each of the disc stars, with that of the perturber, $Omega_{rm p}$, with a phase-difference of $90^circ$, for all stars whose maximum possible $dot{Omega}$ (maximised over all values of $Omega$ for all the disc stars), is greater than $dot{Omega}_{rm p}$; this corresponds approximately to all stars whose semi-major axes are less than twice that of the perturber. This persists until the perturber enters the disc. The predictions of this model agree with a suite of numerical $N$-body simulations which we perform to explore this phenomenon, for a wide range of initial conditions, masses, emph{etc.}, and are an instance of a general phenomenon. Similar effects could occur in the context of planetary systems, too. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.14784v1
The effect of saturated thermal conduction on clouds in a hot plasma by Bastian Sander et al. on Monday 28 November We numerically investigate the internal evolution of multiphase clouds, which are at rest with respect to an ambient, highly ionized medium (HIM) representing the hot component of the circumgalactic medium (CGM). Time-dependent saturated thermal conduction and its implications like condensation rates and mixing efficiency are assessed in multiphase clouds. Our simulations are carried out by using the adaptive mesh refinement code Flash. We perform a grid of models of which we present here those characteristic for the presented study. The model clouds are initially in both hydrostatic and thermal equilibrium and are in pressure balance with the HIM. Thus, they have steep gradients in both temperature and density at the interface to HIM leading to non-negligible thermal conduction. Several physical processes are considered numerically or semi-analytically: thermal conduction, radiative cooling and external heating of gas, self-gravity, mass diffusion, and dissociation of molecules and ionization of atoms. It turns out that saturated thermal conduction triggers a continuous condensation irrespective of cloud mass. Dynamical interactions with ambient HIM all relate to the radial density gradient in the clouds: (1) mass flux due to condensation is the higher the more homogeneous the clouds are; (2) mixing of condensed gas with cloud gas is easier in low-mass clouds, because of their shallower radial density gradient; thus (3) accreted gas is distributed more efficiently. A distinct and sub-structured transition zone forms at the interface between cloud and HIM, which starts at smaller radii and is much narrower as deduced from analytical theory. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.15284v1
The dynamical state of the globular clusters Rup 106 and IC 4499 by Giacomo Beccari et al. on Thursday 24 November The dynamical evolution of globular clusters is theoretically described by a series of well known events typical of N-body systems. Still, the identification of observational signatures able to empirically describe the stage of dynamical evolution of a stellar system of the density typical of a globular cluster, represents a challenge. In this paper we study the dynamical age of the globular clusters Rup 106 and IC 4499. To this aim, we study the radial distribution of the Blue Straggler Stars via the A+ parameter and of the slope of the Main Sequence Mass Function. Both tracers show that Rup 106 and IC 4499 are dynamically young clusters where dynamical friction has just started to segregate massive stars towards the clusters' centre. In fact, we observe that the Blue Straggler stars are more centrally concentrated in both clusters than the reference population. On the same line, we find that in both cases the slope of the mass function significantly decreases as a function of the cluster-centric distances. This result provides additional support for the use of the the radial distribution of the blue stragglers as a powerful observationally convenient indicator of the cluster dynamical age. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.12884v1
The dynamical state of the globular clusters Rup 106 and IC 4499 by Giacomo Beccari et al. on Wednesday 23 November The dynamical evolution of globular clusters is theoretically described by a series of well known events typical of N-body systems. Still, the identification of observational signatures able to empirically describe the stage of dynamical evolution of a stellar system of the density typical of a globular cluster, represents a challenge. In this paper we study the dynamical age of the globular clusters Rup 106 and IC 4499. To this aim, we study the radial distribution of the Blue Straggler Stars via the A+ parameter and of the slope of the Main Sequence Mass Function. Both tracers show that Rup 106 and IC 4499 are dynamically young clusters where dynamical friction has just started to segregate massive stars towards the clusters' centre. In fact, we observe that the Blue Straggler stars are more centrally concentrated in both clusters than the reference population. On the same line, we find that in both cases the slope of the mass function significantly decreases as a function of the cluster-centric distances. This result provides additional support for the use of the the radial distribution of the blue stragglers as a powerful observationally convenient indicator of the cluster dynamical age. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.12884v1
Understanding the role of morphology and environment on the dynamical evolution of isolated galaxy triplets by P. Vásquez-Bustos et al. on Tuesday 22 November The environment where galaxies reside affects their evolutionary histories. Galaxy triplets (systems composed of three physically bound galaxies) constitute one of simplest group of galaxies and are therefore excellent laboratories to study evolutionary mechanisms where effects of the environment are minimal. We present a statistical study of the dynamical properties of isolated galaxy triplets as a function of their local and large scale environments. To explore the connection of the dynamical evolution on the systems with the evolution of the galaxies composing the triplets, we consider observational properties as morphology and star formation rate (SFR). We used the SDSS-based catalog of Isolated Triplets (SIT), which contains 315 triplets. We classified each triplet according to galaxy morphologies and defined a parameter $Q_{trip}$ to quantify the total local tidal strengths in the systems. To quantify the dynamical stage of the system we used the parameters harmonic radius, $R_H$, velocity dispersion, $sigma_{vr}$, crossing time, $H_0t_c$, and virial mass, $M_{vir}$. Triplets composed of three early type galaxies present smallest $R_H$, indicating that they are in general more compact than triplets with one or more late type galaxies. Among triplets with low values of $R_H$ and $H_0t_c$, SIT triplets with $Q_{trip}$-2 show compact configurations due to interactions within the system, such as on-going mergers. We found that there is no dominant galaxy in triplets in terms of properties of stellar populations such as global colour and SFR. Moreover, the global SFR in isolated triplets composed of two or more early-type galaxies increases with the stellar mass ratio of the galaxies with respect to the central galaxy, therefore the system is globally 'rejuvenated'. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.10290v1
GRaM-X: A new GPU-accelerated dynamical spacetime GRMHD code for Exascale computing with the Einstein Toolkit by Swapnil Shankar et al. on Tuesday 22 November We present GRaM-X (General Relativistic accelerated Magnetohydrodynamics on AMReX), a new GPU-accelerated dynamical-spacetime general relativistic magnetohydrodynamics (GRMHD) code which extends the GRMHD capability of Einstein Toolkit to GPU-based exascale systems. GRaM-X supports 3D adaptive mesh refinement (AMR) on GPUs via a new AMR driver for the Einstein Toolkit called CarpetX which in turn leverages AMReX, an AMR library developed for use by the United States DOE's Exascale Computing Project (ECP). We use the Z4c formalism to evolve the equations of GR and the Valencia formulation to evolve the equations of GRMHD. GRaM-X supports both analytic as well as tabulated equations of state. We implement TVD and WENO reconstruction methods as well as the HLLE Riemann solver. We test the accuracy of the code using a range of tests on static spacetime, e.g. 1D MHD shocktubes, the 2D magnetic rotor and a cylindrical explosion, as well as on dynamical spacetimes, i.e. the oscillations of a 3D TOV star. We find excellent agreement with analytic results and results of other codes reported in literature. We also perform scaling tests and find that GRaM-X shows a weak scaling efficiency of $sim 40-50%$ on 2304 nodes (13824 NVIDIA V100 GPUs) with respect to single-node performance on OLCF's supercomputer Summit. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.17509v2
As a matter of dynamical range -- scale dependent energy dynamics in MHD turbulence by Philipp Grete et al. on Monday 21 November Magnetized turbulence is ubiquitous in many astrophysical and terrestrial plasmas but no universal theory exists. Even the detailed energy dynamics in magnetohydrodynamic (MHD) turbulence are still not well understood. We present a suite of subsonic, super-Alfv'enic, high plasma-beta MHD turbulence simulations that only vary in their dynamical range, i.e., in their separation between the large-scale forcing and dissipation scales, and their dissipation mechanism (implicit large eddy simulation, ILES, versus and direct numerical simulation, DNS). Using an energy transfer analysis framework we calculate the effective, numerical viscosities and resistivities and demonstrate and that all ILES calculations of MHD turbulence are resolved and correspond to an equivalent visco-resistive MHD turbulence calculation. Increasing the number of grid points used in an ILES corresponds to lowering the dissipation coefficients, i.e., larger (kinetic and magnetic) Reynolds numbers for a constant forcing scale. Independently, we use this same framework to demonstrate that -- contrary to hydrodynamic turbulence -- the cross-scale energy fluxes are not constant in MHD turbulence. This applies both to different mediators (such as cascade processes or magnetic tension) for a given dynamical range as well as to a dependence on the dynamical range itself, which determines the physical properties of the flow. We do not observe any indication of convergence even at the highest resolution (largest Reynolds numbers) simulation at $2{,}048^3$ cells, calling into question whether an asymptotic regime in MHD turbulence exists, and, if so, what it looks like. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.09750v1
GRaM-X: A new GPU-accelerated dynamical spacetime GRMHD code for Exascale computing with the Einstein Toolkit by Swapnil Shankar et al. on Monday 21 November We present GRaM-X (General Relativistic accelerated Magnetohydrodynamics on AMReX), a new GPU-accelerated dynamical-spacetime general relativistic magnetohydrodynamics (GRMHD) code which extends the GRMHD capability of Einstein Toolkit to GPU-based exascale systems. GRaM-X supports 3D adaptive mesh refinement (AMR) on GPUs via a new AMR driver for the Einstein Toolkit called CarpetX which in turn leverages AMReX, an AMR library developed for use by the United States DOE's Exascale Computing Project (ECP). We use the Z4c formalism to evolve the equations of GR and the Valencia formulation to evolve the equations of GRMHD. GRaM-X supports both analytic as well as tabulated equations of state. We implement TVD and WENO reconstruction methods as well as the HLLE Riemann solver. We test the accuracy of the code using a range of tests on static spacetime, e.g. 1D MHD shocktubes, the 2D magnetic rotor and a cylindrical explosion, as well as on dynamical spacetimes, i.e. the oscillations of a 3D TOV star. We find excellent agreement with analytic results and results of other codes reported in literature. We also perform scaling tests and find that GRaM-X shows a weak scaling efficiency of $sim 40-50%$ on 2304 nodes (13824 NVIDIA V100 GPUs) with respect to single-node performance on OLCF's supercomputer Summit. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.17509v2
DEMNUni: comparing nonlinear power spectra prescriptions in the presence of massive neutrinos and dynamical dark energy by G. Parimbelli et al. on Monday 21 November We provide an accurate comparison, against large cosmological $N$-body simulations, of different prescriptions for modelling nonlinear matter power spectra in the presence of massive neutrinos and dynamical dark energy. We test the current most widely used approaches: fitting functions (HALOFIT and HMcode), the halo-model reaction (ReACT) and emulators (baccoemu and EuclidEmulator2). Focussing on redshifts $zleq2$ and scales $klesssim 1 h/$Mpc (where the simulation mass resolution provides $sim 1%$ accuracy), we find that HMcode and ReACT considerably improve over the HALOFIT prescriptions of Smith and Takahashi (both combined with the Bird correction), with an overall agreement of 2% for all the cosmological scenarios considered. Concerning emulators, we find that, especially at low redshifts, EuclidEmulator2 remarkably agrees with the simulated spectra at $lesssim 1%$ level in scenarios with dynamical dark energy and massless neutrinos, reaching a maximum difference of $sim 2%$ at $z=2$. baccoemu has a similar behaviour as EuclidEmulator2, except for a couple of dark energy models. In cosmologies with massive neutrinos, at $z=0$ all the nonlinear prescriptions improve their agreement with respect to the massless neutrino case, except for the Bird and TakaBird models which, however, are not tailored to $w_0$--$w_a$ models. At $z>0$ we do not find a similar improvement when including massive neutrinos, probably due to the lower impact of neutrino free-streaming at higher redshifts; rather at $z=2$ EuclidEmulator2 exceeds $2%$ agreement for some dark energy equation of state. When considering ratios between the matter power spectrum computed in a given cosmological model and its $Lambda$CDM counterpart, all the tested prescriptions agree with simulated data, at sub-percent or percent level, depending on $z$. [ABRIDGED] arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2207.13677v2
Astrometric Accelerations as Dynamical Beacons: Discovery and Characterization of HIP 21152 B, the First T-Dwarf Companion in the Hyades by Kyle Franson et al. on Monday 21 November Benchmark brown dwarf companions with well-determined ages and model-independent masses are powerful tools to test substellar evolutionary models and probe the formation of giant planets and brown dwarfs. Here, we report the independent discovery of HIP~21152~B, the first imaged brown dwarf companion in the Hyades, and conduct a comprehensive orbital and atmospheric characterization of the system. HIP~21152 was targeted in an ongoing high-contrast imaging campaign of stars exhibiting proper motion changes between Hipparcos and Gaia, and was also recently identified by Bonavita et al. (2022) and Kuzuhara et al. (2022). Our Keck/NIRC2 and SCExAO/CHARIS imaging of HIP~21152 revealed a comoving companion at a separation of $0.37^{primeprime}$ (16 au). We perform a joint orbit fit of all available relative astrometry and radial velocities together with the Hipparcos-Gaia proper motions, yielding a dynamical mass of $24^{+6}_{-4},mathrm{M_{Jup}}$, which is $1{-}2{sigma}$ lower than evolutionary model predictions. Hybrid grids that include the evolution of cloud properties best reproduce the dynamical mass. We also identify a comoving wide-separation ($1837^{primeprime}$ or $7.9 times 10^4 , mathrm{au}$) early-L dwarf with an inferred mass near the hydrogen-burning limit. Finally, we analyze the spectra and photometry of HIP~21152~B using the Saumon & Marley (2008) atmospheric models and a suite of retrievals. The best-fit grid-based models have $f_{mathrm{sed}}=2$, indicating the presence of clouds, $T_{mathrm{eff}}=1400 , mathrm{K}$, and $log{g}=4.5 , mathrm{dex}$. These results are consistent with the object's spectral type of $mathrm{T0pm1}$. As the first benchmark brown dwarf companion in the Hyades, HIP~21152~B joins the small but growing number of substellar companions with well-determined ages and dynamical masses. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.09840v1
Understanding the role of morphology and environment on the dynamical evolution of isolated galaxy triplets by P. Vásquez-Bustos et al. on Monday 21 November The environment where galaxies reside affects their evolutionary histories. Galaxy triplets (systems composed of three physically bound galaxies) constitute one of simplest group of galaxies and are therefore excellent laboratories to study evolutionary mechanisms where effects of the environment are minimal. We present a statistical study of the dynamical properties of isolated galaxy triplets as a function of their local and large scale environments. To explore the connection of the dynamical evolution on the systems with the evolution of the galaxies composing the triplets, we consider observational properties as morphology and star formation rate (SFR). We used the SDSS-based catalog of Isolated Triplets (SIT), which contains 315 triplets. We classified each triplet according to galaxy morphologies and defined a parameter $Q_{trip}$ to quantify the total local tidal strengths in the systems. To quantify the dynamical stage of the system we used the parameters harmonic radius, $R_H$, velocity dispersion, $sigma_{vr}$, crossing time, $H_0t_c$, and virial mass, $M_{vir}$. Triplets composed of three early type galaxies present smallest $R_H$, indicating that they are in general more compact than triplets with one or more late type galaxies. Among triplets with low values of $R_H$ and $H_0t_c$, SIT triplets with $Q_{trip}$-2 show compact configurations due to interactions within the system, such as on-going mergers. We found that there is no dominant galaxy in triplets in terms of properties of stellar populations such as global colour and SFR. Moreover, the global SFR in isolated triplets composed of two or more early-type galaxies increases with the stellar mass ratio of the galaxies with respect to the central galaxy, therefore the system is globally 'rejuvenated'. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.10290v1
Understanding the role of morphology and environment on the dynamical evolution of isolated galaxy triplets by P. Vásquez-Bustos et al. on Monday 21 November The environment where galaxies reside affects their evolutionary histories. Galaxy triplets (systems composed of three physically bound galaxies) constitute one of simplest group of galaxies and are therefore excellent laboratories to study evolutionary mechanisms where effects of the environment are minimal. We present a statistical study of the dynamical properties of isolated galaxy triplets as a function of their local and large scale environments. To explore the connection of the dynamical evolution on the systems with the evolution of the galaxies composing the triplets, we consider observational properties as morphology and star formation rate (SFR). We used the SDSS-based catalog of Isolated Triplets (SIT), which contains 315 triplets. We classified each triplet according to galaxy morphologies and defined a parameter $Q_{trip}$ to quantify the total local tidal strengths in the systems. To quantify the dynamical stage of the system we used the parameters harmonic radius, $R_H$, velocity dispersion, $sigma_{vr}$, crossing time, $H_0t_c$, and virial mass, $M_{vir}$. Triplets composed of three early type galaxies present smallest $R_H$, indicating that they are in general more compact than triplets with one or more late type galaxies. Among triplets with low values of $R_H$ and $H_0t_c$, SIT triplets with $Q_{trip}$-2 show compact configurations due to interactions within the system, such as on-going mergers. We found that there is no dominant galaxy in triplets in terms of properties of stellar populations such as global colour and SFR. Moreover, the global SFR in isolated triplets composed of two or more early-type galaxies increases with the stellar mass ratio of the galaxies with respect to the central galaxy, therefore the system is globally 'rejuvenated'. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.10290v1
TOI-1136 is a Young, Coplanar, Aligned Planetary System in a Pristine Resonant Chain by Fei Dai et al. on Tuesday 18 October Convergent disk migration has long been suspected to be responsible for forming planetary systems with a chain of mean-motion resonances (MMR). Dynamical evolution over time could disrupt the delicate resonant configuration. We present TOI-1136, a 700-Myr-old G star hosting at least 6 transiting planets between $sim$2 and 5 $R_oplus$. The orbital period ratios deviate from exact commensurability by only $10^{-4}$, smaller than the $sim$,$10^{-2}$ deviations seen in typical Kepler near-resonant systems. A transit-timing analysis measured the masses of the planets (3-8$M_oplus$) and demonstrated that the planets in TOI-1136 are in true resonances with librating resonant angles. Based on a Rossiter-McLaughlin measurement of planet d, the star's rotation appears to be aligned with the planetary orbital planes. The well-aligned planetary system and the lack of detected binary companion together suggest that TOI-1136's resonant chain formed in an isolated, quiescent disk with no stellar fly-by, disk warp, or significant axial asymmetry. With period ratios near 3:2, 2:1, 3:2, 7:5, and 3:2, TOI-1136 is the first known resonant chain involving a second-order MMR (7:5) between two first-order MMR. The formation of the delicate 7:5 resonance places strong constraints on the system's migration history. Short-scale (starting from $sim$0.1 AU) Type-I migration with an inner disk edge is most consistent with the formation of TOI-1136. A low disk surface density ($Sigma_{rm 1AU}lesssim10^3$g~cm$^{-2}$; lower than the minimum-mass solar nebula) and the resultant slower migration rate likely facilitated the formation of the 7:5 second-order MMR. TOI-1136's deep resonance suggests that it has not undergone much resonant repulsion during its 700-Myr lifetime. One can rule out rapid tidal dissipation within a rocky planet b or obliquity tides within the largest planets d and f. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.09283v1
TOI-1136 is a Young, Coplanar, Aligned Planetary System in a Pristine Resonant Chain by Fei Dai et al. on Tuesday 18 October Convergent disk migration has long been suspected to be responsible for forming planetary systems with a chain of mean-motion resonances (MMR). Dynamical evolution over time could disrupt the delicate resonant configuration. We present TOI-1136, a 700-Myr-old G star hosting at least 6 transiting planets between $sim$2 and 5 $R_oplus$. The orbital period ratios deviate from exact commensurability by only $10^{-4}$, smaller than the $sim$,$10^{-2}$ deviations seen in typical Kepler near-resonant systems. A transit-timing analysis measured the masses of the planets (3-8$M_oplus$) and demonstrated that the planets in TOI-1136 are in true resonances with librating resonant angles. Based on a Rossiter-McLaughlin measurement of planet d, the star's rotation appears to be aligned with the planetary orbital planes. The well-aligned planetary system and the lack of detected binary companion together suggest that TOI-1136's resonant chain formed in an isolated, quiescent disk with no stellar fly-by, disk warp, or significant axial asymmetry. With period ratios near 3:2, 2:1, 3:2, 7:5, and 3:2, TOI-1136 is the first known resonant chain involving a second-order MMR (7:5) between two first-order MMR. The formation of the delicate 7:5 resonance places strong constraints on the system's migration history. Short-scale (starting from $sim$0.1 AU) Type-I migration with an inner disk edge is most consistent with the formation of TOI-1136. A low disk surface density ($Sigma_{rm 1AU}lesssim10^3$g~cm$^{-2}$; lower than the minimum-mass solar nebula) and the resultant slower migration rate likely facilitated the formation of the 7:5 second-order MMR. TOI-1136's deep resonance suggests that it has not undergone much resonant repulsion during its 700-Myr lifetime. One can rule out rapid tidal dissipation within a rocky planet b or obliquity tides within the largest planets d and f. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.09283v1
TOI-1136 is a Young, Coplanar, Aligned Planetary System in a Pristine Resonant Chain by Fei Dai et al. on Tuesday 18 October Convergent disk migration has long been suspected to be responsible for forming planetary systems with a chain of mean-motion resonances (MMR). Dynamical evolution over time could disrupt the delicate resonant configuration. We present TOI-1136, a 700-Myr-old G star hosting at least 6 transiting planets between $sim$2 and 5 $R_oplus$. The orbital period ratios deviate from exact commensurability by only $10^{-4}$, smaller than the $sim$,$10^{-2}$ deviations seen in typical Kepler near-resonant systems. A transit-timing analysis measured the masses of the planets (3-8$M_oplus$) and demonstrated that the planets in TOI-1136 are in true resonances with librating resonant angles. Based on a Rossiter-McLaughlin measurement of planet d, the star's rotation appears to be aligned with the planetary orbital planes. The well-aligned planetary system and the lack of detected binary companion together suggest that TOI-1136's resonant chain formed in an isolated, quiescent disk with no stellar fly-by, disk warp, or significant axial asymmetry. With period ratios near 3:2, 2:1, 3:2, 7:5, and 3:2, TOI-1136 is the first known resonant chain involving a second-order MMR (7:5) between two first-order MMR. The formation of the delicate 7:5 resonance places strong constraints on the system's migration history. Short-scale (starting from $sim$0.1 AU) Type-I migration with an inner disk edge is most consistent with the formation of TOI-1136. A low disk surface density ($Sigma_{rm 1AU}lesssim10^3$g~cm$^{-2}$; lower than the minimum-mass solar nebula) and the resultant slower migration rate likely facilitated the formation of the 7:5 second-order MMR. TOI-1136's deep resonance suggests that it has not undergone much resonant repulsion during its 700-Myr lifetime. One can rule out rapid tidal dissipation within a rocky planet b or obliquity tides within the largest planets d and f. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.09283v1
TOI-1136 is a Young, Coplanar, Aligned Planetary System in a Pristine Resonant Chain by Fei Dai et al. on Tuesday 18 October Convergent disk migration has long been suspected to be responsible for forming planetary systems with a chain of mean-motion resonances (MMR). Dynamical evolution over time could disrupt the delicate resonant configuration. We present TOI-1136, a 700-Myr-old G star hosting at least 6 transiting planets between $sim$2 and 5 $R_oplus$. The orbital period ratios deviate from exact commensurability by only $10^{-4}$, smaller than the $sim$,$10^{-2}$ deviations seen in typical Kepler near-resonant systems. A transit-timing analysis measured the masses of the planets (3-8$M_oplus$) and demonstrated that the planets in TOI-1136 are in true resonances with librating resonant angles. Based on a Rossiter-McLaughlin measurement of planet d, the star's rotation appears to be aligned with the planetary orbital planes. The well-aligned planetary system and the lack of detected binary companion together suggest that TOI-1136's resonant chain formed in an isolated, quiescent disk with no stellar fly-by, disk warp, or significant axial asymmetry. With period ratios near 3:2, 2:1, 3:2, 7:5, and 3:2, TOI-1136 is the first known resonant chain involving a second-order MMR (7:5) between two first-order MMR. The formation of the delicate 7:5 resonance places strong constraints on the system's migration history. Short-scale (starting from $sim$0.1 AU) Type-I migration with an inner disk edge is most consistent with the formation of TOI-1136. A low disk surface density ($Sigma_{rm 1AU}lesssim10^3$g~cm$^{-2}$; lower than the minimum-mass solar nebula) and the resultant slower migration rate likely facilitated the formation of the 7:5 second-order MMR. TOI-1136's deep resonance suggests that it has not undergone much resonant repulsion during its 700-Myr lifetime. One can rule out rapid tidal dissipation within a rocky planet b or obliquity tides within the largest planets d and f. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2210.09283v1
Hey Everyone, Today, we have another amazing guest. It's Esteban Moro (1)!Esteban is a researcher, data scientist and professor at Universidad Carlos III (UC3M) in Spain and Visiting Professor at MIT Media Lab and MIT Connection Science at IDSS. Previously, I was researcher at University of Oxford. He is a native of Salamanca (Spain) … we talk about that … and hold a PhD in Physics.Esteban's work lies in the intersection of big data and computational social science, with special attention to human dynamics, collective intelligence, social networks and urban mobility in problems like viral marketing, natural disaster management, or economical segregation in cities. Esteban is creative and exploring in his work, and has made important contributions in a number of topics, especially recently using massive datasets to understand problems like how humans communicate, how to political opinion spreads in social networks or building alternative wellbeing indexes. His work has appeared in major journals including PNAS or Science Advances and is regularly covered by media outlets The Atlantic, The Washington Post, The Wall Street Journal, El País (Spain).In our conversation, we talk about his career, his science, and go deep with his 2011 paper “Dynamical strength of social ties in information spreading” (2), which is not only an interesting paper … but also comes with a very nice story of how we can build communities in science by collaborating even between competing groups.References(1) http://estebanmoro.org(2) https://journals.aps.org/pre/abstract/10.1103/PhysRevE.83.045102CreditsThe podcast has theme music by Waylon Thornton (and a little bit by me as well). WT's songs are "American Heart" and "Seven". Via freemusicarchive.org and licenced under CC BY-NC-SA. The podcast was funded in part by the Villum Foundation.
Hello Interactors, There’s but a short window of time When the dirt is in its prime Not too cold or wet Or the seeds will not set Last week the fields were lakes This week the soil bakes Gone is the mud and grime So into the tractors they all climbIt’s time to get those seeds in the ground! If you have the space. The state of Iowa, where I grew up, has this as their slogan: ‘A Place to Grow’. But those places are being displaced by homes at a record pace.As interactors, you’re special individuals self-selected to be a part of an evolutionary journey. You’re also members of an attentive community so I welcome your participation.Please leave your comments below or email me directly.Now let’s go…GROW BABY GROWWe bought our first corn on the cob this week. It’s from California. Growing up in Iowa we didn’t see corn until late summer. To get corn stalks to be ‘knee high by the fourth of July’ meant getting the seeds in the ground by the end of May. That’s now. Iowa farmers have been stressed out these last couple weeks. The planting window was closing fast and the state was getting unseasonable rain and cold temperatures. Ten days ago one farmer in northeast Iowa said he could ride his boat across his fields.Such is the life of a farmer. But the weather turned in their favor this week. They’ve been busy. On May 23rd the USDA reported 86% of Iowa’s corn crop had been planted and 47% of seeds planted earlier are already sprouting. But corn, soybeans, and oats are all behind schedule. Let’s hope the wacky weather patterns don’t wreak havoc on these weathered wonder-workers. I like my corn tortillas, tofu, and oat milk. Though, most Iowa grains and soybeans are fed to livestock, not people.And we know people like their burgers and bacon. Increased commodity prices are the number one reason some farmers give for why farmland value in Iowa is through the roof. Last year a farmer in Eastern Iowa’s Johnson County made headlines when he sold 40 acres of two 80-acre tracts for $26,000 per acre. That’s over $2,000,000 for 40 acres (the equivalent of 20 soccer fields).But that pricey southern most 40 acres is comprised of Klinger soil – a claylike sandy substrate formed by glacier tills. This soil is perfect for the native prairie grass but crops struggle. So this opportunistic farmer decided to plant a more profitable crop that has no agricultural value at all. Houses. He sold the worst soil for the most money to a developer who is expanding the sprawl of a nearby small town city called Swisher; population 914. It’s a 15 minute drive south of Iowa’s second largest city, Cedar Rapids.The conversion of farmland into housing developments is a common sight across Iowa. The U.S. Department of Agriculture (USDA) does an agricultural census every five years and the last one was done in 2017. The 2022 version is due later this year. From 2012 to 2017 Iowa lost 2,533 farms. That leaves 86,104 farms remaining. There were over 10,000 more farms in 1997 and nearly 20,000 more when I left Iowa in 1984. The amount of land dedicated to farming shrank by 59,000 acres.Much of this reduction is from consolidation. The number of large farms (>2000 acres) grew 15% to 1,892 over five years. By comparison, there were barely 300 large farms in 1987. From 2012 to 2017 large farms had gobbled 10% of up mid-sized farms (500-999 acres). Small farms (fewer than 9 acres) grew 36% to 9,120. That’s a big jump in five years, but only 1000 more than 30 years ago.These figures from the USDA tell the story of farmland consolidation across Iowa since the 1980s. But to get a picture of how farmland sold to developers contributes to the sprawl of urban areas, more and more researchers are turning to satellite imagery. In 2018 two researchers from Iowa State University were lead authors on a paper demonstrating novel image processing techniques for mapping the dynamics of urban growth. They took a series of satellite images from 1985 to 2015 of a region encompassing the Des Moines Metropolitan Area. They then trained software to differentiate between the natural and built environment by looking at the color of the pixels in the images. Pixels turning from looking ‘natural’ to looking ‘urban’ over time revealed a growing gray blob of concrete known as urban sprawl.They found, with 90% accuracy, that the Des Moines Metropolitan Area urban boundary more than doubled between 1985 and 2015. Over those thirty years the area grew linearly from 58 square miles in 1985 to just over 135 square miles in 2015. Most of which, of course, was farmland. At this growth rate, it will continue to double again every 30 years.Area growth like this is usually the result of an increasing population. The Des Moines Metropolitan Area is no exception. From 2010 to 2020, the population in this area grew 17% from 606,465 to 709,466. You might imagine the city of Des Moines being at the heart of this growth given it’s the center of the metropolitan area, but you’d be wrong. Of the top ten most populated cities in the area, Des Moines proper grew the least at 5.3% and has been relatively flat for decades. The fastest growing city from 2010 to 2020 was a town just north of Des Moines called Grimes. It grew a whopping 87%. Another town to the north, Ankeny, was second at 49% and my home town, Norwalk, just to the south, grew the third fastest at 43%.These are some of the fastest growing cities in the country. Impressive. Until you consider the overall population of the state of Iowa only grew 4.8% compared to the U.S. population rate of 7.4%.It's a curious fact that the Des Moines Metropolitan Area is growing in population at a rate far greater than the state is. This means Iowans are 1) moving to metropolitan areas from rural areas, 2) between cities within a metropolitan area, or 3) to another state all together. I reached out to a friend who recently moved from West Des Moines to Des Moines after they became empty nesters. He said they didn’t need as big a house and wanted to be closer to restaurants and entertainment. His wife added that they looked at surrounding suburbs but the house in Des Moines offered the best value.I then contacted another friend who sells real estate in the area. She told me people are obsessed with new construction. Her clients repeat the same refrain, “I want a new kitchen with granite countertops, white cabinets, and a tile floor.” My friend has an eye for houses with good bones and an affinity for mid-century classics. She tries to sell their vision to her clients by fixing up these older homes, but there’s little interest. She said, “It’s like so much else in their life. Out with the old, in with the new. Why fix it when a new one will due?” So she spends a lot of time driving to the fringes showing new construction in cities like Grimes, Ankeny, and Norwalk.THE RADICAL, THE DYNAMICAL, AND THE MEGLOMANIACAL The hollowing out of city centers as people move to the fringes, the ‘donuting’ of metropolitan areas, is common. Especially in the Midwest. Detroit gets all the attention, but the rust belt is filled with them. It occurs in cities around the world.In 1969, a professor from the MIT Sloan School of Management, Jay Wright Forrester, developed a theory and computer model for this phenomenon in a booked titled Urban Dynamics. If you’ve ever played the computer game SimCity then you have Forrester to thank. The game is built on his model. We have many things for which to thank Forrester. He helped to invent random access computer memory (RAM). He was also a pioneer in computer graphics before computers; he figured out how to get a ball to bounce on an oscilloscope screen. And the current reverberations of supply chain perturbations is called the Forrester Effect as described in his 1961 book called Industrial Dynamics. Forrester is thus the founder of the field of system dynamics – the study of nonlinear behavior of complex systems over time. And cities are indeed complex systems…mostly due to the complexities of human behavior.Forrester’s book was groundbreaking but also controversial. To validate the theory with an actual city, the U.S. Department of Housing and Urban Development (HUD) – which was also five years old at the time – sponsored a two year study. Four cities were chosen as cites in 1971 and they were all within a 40 mile radius of MIT. The first experimental city was Lowell, Massachusetts.Louis Alfeld was the Director of the program. In 1994 – on the 25th anniversary of the publishing of Urban Dynamics – he reflected on the execution of the experiments and the lack of progress since. The effect of human behavior on complex systems is apparent even in the administration of the study. HUD assigned the harshest critics of the theory to be on the committee which complicated things from the start. Alfeld recalls,“Although we attempted to engage the committee in a constructive dialogue concerning the model’s utility, the members had neither the time nor the inclination to study system dynamics. Criticisms concerning data and validation techniques displaced issues of system structure and user needs. Neither side understood the other’s point of view.”Because HUD committee members were trained in traditional economics and only trusted well-cited existing academic literature, they continually dismissed and rejected every premise of systems theory. It prompted Forrester himself to respond with these words,“It is unfortunate that you have not found it possible to spend more time with us in order to better understand system dynamics and its application to the dynamic modeling of social systems. Many of the issues you raise seem to rest on assumptions that reflect practices in other kinds of modeling but which do not apply in the same way to system dynamics models. In fact, the strength of system dynamics arises from these differences.”In contrast to HUD’s skepticism, Forrester and Alfeld found the leadership at Lowell to be more open to these theories. Their city was in decay after falling ungracefully from a century of manufacturing success. Their buildings were crumbling and the city faced a persistent 12% unemployment rate. They were eager to try something new.One of the foundations of urban dynamics centers on available land as a resource. Defined as a nonlinear function, it says the rate of construction is constrained by the amount of land on which to build. New cities start out with abundant land, but being the first company to build comes with risk. Will employees follow? Will the resources be available to turn a profit? But one building can attract more buildings and if all goes well the competition for good land increases and growth, fueled by demand, explodes. This in turn inflates the price of attractive available land. Inflation then slows growth until all the land is consumed and new construction halts. Over time these buildings decay, businesses fold, and the city begins to decline economically and socially as people and customers leave. The only way a city constrained by space can maintain equilibrium in this closed system is to tear down old buildings and build anew on existing land. This was the fate Lowell faced.The city government enacted policies that reflected the theory of urban dynamics. They created incentives to local companies to remodel existing buildings and expand business. They took steps to curb further deterioration of existing housing left vacant by affluent residents who fled. This in turn made more housing accessible to lower income residents who rushed the city like a flood. These policies resulted in strict codes that forced a refurbishing and reinvestment in the city.After two years Lowell showed signs of improving. Alfeld and the city were encouraged to keep experimenting. But HUD had encouraged the city to set the parameters of the model to mimic metrics from Lowell’s previous historic economic boom the century prior. Falling short of these expectations in two years, the committee was not convinced Forrester’s theory of urban dynamics resulted in sufficient enough of an improvement to continue.Hard quantitative evidence these traditional economists demanded was indeed lacking, in part due to HUD’s inability to operate a mainframe. But in the end the committee seemed more interested in the numbers than in the positive qualitative effects evident in the city and its residents. As Alfeld grimly summarizes,“The interface gap between model and critic contributed to the communication gap. In the final accounting, neither our success in Lowell nor our outpouring of reports and papers could bridge that gap. HUD judged that we had nothing to offer and urban dynamics dropped out of academic sight, its potential contribution to resolving America’s urban crisis ignored for the past quarter-century.”THE AGING ARIAN AGRARIANThe Des Moines Metropolitan Area is not space constrained like Lowell, Massachusetts. And while the city of Des Moines has reinvigorated the downtown area, the seemingly unlimited surrounding land availability and patterns of sprawl reveal no intention to contain the sprawl, protect farmland (or natural grassland) and reinvest in what is already built. This will likely lead to each inner concentric ring of the donut hole to age and decline just as the city of Des Moines did. This will create a larger donut hole in the center as the outer perimeter of the donut continues to encroach on more and more prime farmland. Land that is owned by dying farmers.One Iowa State University study revealed that “in 2017, over half the farmland (60 percent) in Iowa was owned by people over the age of 65. This was five percentage points higher than in 2007, and twice the level in 1982. In addition, farmland owners who were 75 years or older owned a record 35 percent of all acres in Iowa as of July 2017.” A 2021 study showed that “Iowa farmland owners are older than the general population. On average, the full-time and part-time farmers in [the] study were 62 years old. The retired farmers were, on average, 77.7 years old, and the non-farmer owners were 68.7 years old.” Non-farmers can include surviving spouses who don’t farm or off-farm heirs to the land. Also, “Of the farmland [] analyzed, 29.5% was owned by full-time farmers, 12.9% by parttime farmers, 22.7% by retired farmers, and 34.9% by non-farming owners.” With 60% of farmland owned by soon-to-be retirees and a sizable portion of 35% owned by heirs who’d rather have the money than to farm, what does this say about the future of farming in Iowa?Iowa, and the country, has a farming succession problem. One study suggests that lack of knowledge transfer and co-creation of crop yields will be one of the biggest challenges facing the foodscape of the Midwest. But when it comes to succession strategies, the Iowa farmers in this study,“were on average motivated strongly by social factors—e.g., desires to maintain agrarian cultures, rural communities, and family farms. (It is worth mentioning that these sentiments could be colored by the fact that these were also established growers—e.g., those privileged by policies like the Farm Bill—who were well capitalized and could afford to focus on non-economic factors.)”That’s not to say these farmers haven’t suffered economic hardship. And the economics of farming are complicated and messy. But this researcher found new farmers to more interested in the sustainability of the land and in farming than those who inherited a farm. Those farmers are now looking to retire and their children typically aren’t interested in farming. The author continues,“Intergenerational knowledge transfer, from one generation to the next (though not necessarily within the same family), is a critical element in the creation of foodscapes populated with farms of all scales and commodity profiles and by farmers from diverse socio-economic backgrounds, including farm/nonfarm backgrounds, genders, sexual orientations, ethnicities, and religions.”This requires building communities that welcome this kind of diversity, which most do not. People from Myanmar is one of Des Moines fastest growing minority groups, but an ethnic minority advocacy group says, “It's very challenging. I talk to my friends on the coasts. People (without family here) don't want to move to Iowa…In Iowa, we don't have investments and resources for immigrants, for refugee-led, community-based groups."There are groups trying to help. For example, The Practical Farmers of Iowa have been working since 1985 to “equip farmers to build resilient farms and communities.” Also, there’s the Women Food and Agriculture Network whose “mission is to engage women in building an ecological and just food and agricultural system through individual and community power.” Many of those fast growing small farms in Iowa fit the profile of these groups. It’s an encouraging sign for the health and diversity of small scale farming in Iowa.But there are only 600 minority farmers in Iowa. What are the odds these aging white male farmers of selling their property to a Myanmar farmer or an ambitious woman graduate from the Iowa State College of Agriculture? How likely is an aging retiree willing teach a black family from the south with farming experience how to grow soybeans in Iowa? If a farmer isn’t willing to co-create or sell their farm to a first generation farmer who isn’t a Christian white heterosexual male who’s interested in perpetuating the ‘old-boys club’, then they’ll likely just sell it to another aging white male farmer like them. This will further consolidate Iowa farmland that will likely end up in a trust fund for their heirs. Many of whom will wait for the expanding urban gray blobs to reach their land and then they’ll likely cash in on a $2,000,000 offer from a real estate developer.And with 81% of Iowa being white, with an estimated 90% of them living in the suburban fringes away from what little diversity there is in Des Moines, you can bet the person buying that newly built white home with granite countertops will be as white as their kitchen cabinets. At the same time, it’s great these families found a good home. I grew up on fertile Iowa soil as part of Norwalk’s first round of sprawl and it benefitted me.Either way at least the seeds got in the ground on time. They can eat that yummy corn on the cob this summer with their hamburger made from Iowa beef. It will all take place on a grassy lawn that once grew the corn they’ll be eating…or the corn that fed the cow in their burger. Come to think of it, maybe their corn will come from California too…and the hamburger. This is a public episode. If you would like to discuss this with other subscribers or get access to bonus episodes, visit interplace.io
Support the show to get full episodes and join the Discord community. Eve discusses many of the lessons she has learned studying a small nervous system, the crustacean stomatogastric nervous system (STG). The STG has only about 30 neurons and its connections and neurophysiology are well-understood. Yet Eve's work has shown it functions under a remarkable diversity of conditions, and does so is a remarkable variety of ways. We discuss her work on the STG specifically, and what her work implies about trying to study much larger nervous systems, like our human brains. The Marder Lab.Twitter: @MarderLab.Related to our conversation:Understanding Brains: Details, Intuition, and Big Data.Emerging principles governing the operation of neural networks (Eve mentions this regarding "building blocks" of neural networks). 0:00 - Intro 3:58 - Background 8:00 - Levels of ambiguity 9:47 - Stomatogastric nervous system 17:13 - Structure vs. function 26:08 - Role of theory 34:56 - Technology vs. understanding 38:25 - Higher cognitive function 44:35 - Adaptability, resilience, evolution 50:23 - Climate change 56:11 - Deep learning 57:12 - Dynamical systems
Richard Shuttleworth has over 20 years coach education and support experience in elite level sport, focusing on skill acquisition. He has worked at the Australian Institute of Sport with Olympic level coaches, various national sporting organisations, Super Rugby franchises, the NRL, Football Federation Australia and Australian Rules clubs. He was the Professional Coach Development Manager for the RFU for 4 years before moving into his latest role as a High Performance Coach Development Consultant. Richard has a BSc in Coaching Science, a MSc in Sport Psychology and a PhD in Skill Acquisition.Twitter: @skillacq
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