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Prototype Analysis in Hopfield Networks With Hebbian Learning.

We discuss prototype formation in the Hopfield network. Typically, Hebbian learning with highly correlated states leads to degraded memory performance. We show that this type of learning can lead to prototype formation, where unlearned states emerge as representatives of large correlated subsets of states, alleviating capacity woes. This process has similarities to prototype learning in human cognition. We provide a substantial literature review of prototype learning in associative memories, covering contributions from psychology, statistical physics, and computer science. We analyze prototype formation from a theoretical perspective and derive a stability condition for these states based on the number of examples of the prototype presented for learning, the noise in those examples, and the number of nonexample states presented. The stability condition is used to construct a probability of stability for a prototype state as the factors of stability change. We also note similarities to traditional network analysis, allowing us to find a prototype capacity. We corroborate these expectations of prototype formation with experiments using a simple Hopfield network with standard Hebbian learning. We extend our experiments to a Hopfield network trained on data with multiple prototypes and find the network is capable of stabilizing multiple prototypes concurrently. We measure the basins of attraction of the multiple prototype states, finding attractor strength grows with the number of examples and the agreement of examples. We link the stability and dominance of prototype states to the energy profile of these states, particularly when comparing the profile shape to target states or other spurious states.

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Crucial role of Aquaporin-4 extended isoform in brain water Homeostasis and Amyloid-β clearance: implications for Edema and neurodegenerative diseases

The water channel aquaporin-4 (AQP4) is crucial for water balance in the mammalian brain. AQP4 has two main canonical isoforms, M23, which forms supramolecular structures called Orthogonal Arrays of Particles (OAP) and M1, which does not, along with two extended isoforms (M23ex and M1ex). This study examines these isoforms’ roles, particularly AQP4ex, which influences water channel activity and localization at the blood-brain barrier. Using mice lacking both AQP4ex isoforms (AQP4ex-KO) and lacking both AQP4M23 isoforms (OAP-null) mice, we explored brain water dynamics under osmotic stress induced by an acute water intoxication (AWI) model. AQP4ex-KO mice had lower basal brain water content than WT and OAP-null mice. During AWI, brain water content increased rapidly in WT and AQP4ex-KO mice, but was delayed in OAP-null mice. AQP4ex-KO mice had the highest water content increase at 20 min. Immunoblot analysis showed stable total AQP4 in WT mice initially, with increases at 30 min. AQP4ex and its phosphorylated form (p-AQP4ex) levels rose quickly, but the p-AQP4ex/AQP4ex ratio dropped at 20 min. AQP4ex-KO mice showed a compensatory rise in canonical AQP4 at 20 min post-AWI. These findings highlight the important role of AQP4ex in water content dynamics in both normal and pathological states. To evaluate brain waste clearance, amyloid-β (Aβ) removal was assessed using a fluorescent Aβ intra-parenchyma injection model. AQP4ex-KO mice demonstrated markedly impaired Aβ clearance, with extended diffusion distances and reduced fluorescence in cervical lymph nodes, indicating inefficient drainage from the brain parenchyma. Mechanistically, the polarization of AQP4 at astrocytic endfeet is essential for efficient clearance flow, aiding interstitial fluid movement into the CSF and lymphatic system. In AQP4ex-KO mice, disrupted polarization forces reliance on slower, passive diffusion for solute clearance, significantly reducing Aβ removal efficiency and altering extracellular space dynamics. Our results underscore the importance of AQP4ex in both brain water homeostasis and solute clearance, particularly Aβ. These findings highlight AQP4ex as a potential therapeutic target for enhancing waste clearance mechanisms in the brain, which could have significant implications for treating brain edema and neurodegenerative diseases like Alzheimer’s.

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J-PLUS: Bayesian object classification with a strum of BANNJOS

With its 12 optical filters, the Javalambre-Photometric Local Universe Survey (J-PLUS) provides an unprecedented multicolor view of the local Universe. The third data release (DR3) covers 3,192 deg$^2$ and contains 47.4 million objects. However, the classification algorithms currently implemented in the J-PLUS pipeline are deterministic and based solely on the morphology of the sources. Our goal is to classify the sources identified in the J-PLUS DR3 images as stars, quasi-stellar objects (QSOs), or galaxies. For this task, we present a machine learning pipeline that utilizes Bayesian neural networks to provide the full probability distribution function (PDF) of the classification. has been trained on photometric, astrometric, and morphological data from J-PLUS DR3 DR3, and using over 1.2 million objects with spectroscopic classification from DR18 DR9, the Early Data Release, and DR3. Results were validated on a test set of about $1.4 10^5$ objects and cross-checked against theoretical model predictions. outperforms all previous classifiers in terms of accuracy, precision, and completeness across the entire magnitude range. It delivers over $95<!PCT!>$ accuracy for objects brighter than $r = 21.5$ mag and $ 90<!PCT!>$ accuracy for those up to $r = 22$ mag, where J-PLUS completeness is $ 25<!PCT!>$. is also the first object classifier to provide the full PDF of the classification, enabling precise object selection for high purity or completeness, and for identifying objects with complex features, such as active galactic nuclei with resolved host galaxies. effectively classified J-PLUS sources into around 20 million galaxies, one million QSOs, and 26 million stars, with full PDFs for each, which allow for later refinement of the sample. The upcoming J-PAS survey, with its 56 color bands, will further enhance 's ability to detail the nature of each source.

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Weekday-to-weekend sleep duration patterns among young adults and outcomes related to health and academic performance

BackgroundTo examine whether weekday-to-weekend sleep duration (WWD) difference and specific WWD patterns are associated with mental and somatic health and academic performance in a student population.MethodsThis study utilized cross-sectional data from the SHoT-2018 survey which includes responses from 50,054 full-time university/college students in Norway. Participants completed online questionnaires and reported sleep duration separately for weekdays and weekends. Medium sleep duration was defined as 7 to 9 h, short sleep duration as < 7 h and long sleep duration as > 9 h. Regression analyses were used to examine whether the degree and patterns of WWD was associated with health-related outcomes and academic performance.ResultsThe mean age of the sample was 23.2 years and comprised of 68.8% women. Most students (81.7%) slept longer on weekends compared to weekdays and 30.0% of the students reported a mean sleep duration shorter than 7 h. WWD difference was positively associated with higher odds of overweight/obesity, dissatisfaction with life, psychological distress, somatic burden and failed study exam. Concerning WWD patterns, the odds of students reporting unfavorably on the outcomes were particularly high for those who slept short on both weekdays and weekends, while those who slept short on weekdays seemed to benefit from sleeping longer (“catching up”) on weekends.ConclusionsOverall, WWD was associated with adverse health outcomes for students. Short sleep duration both on weekday and weekend was associated with the most detrimental outcomes in terms of health and academic performance, while sleeping in on weekends may alleviate some of the detriments.

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