86,538 research outputs found
Parallel Learning by Multitasking Neural Networks
No full textA modern challenge of Artificial Intelligence is learning multiple patterns
at once (i.e.parallel learning). While this can not be accomplished by standard
Hebbian associative neural networks, in this paper we show how the Multitasking
Hebbian Network (a variation on theme of the Hopfield model working on sparse
data-sets) is naturally able to perform this complex task. We focus on systems
processing in parallel a finite (up to logarithmic growth in the size of the
network) amount of patterns, mirroring the low-storage level of standard
associative neural networks at work with pattern recognition. For mild dilution
in the patterns, the network handles them hierarchically, distributing the
amplitudes of their signals as power-laws w.r.t. their information content
(hierarchical regime), while, for strong dilution, all the signals pertaining
to all the patterns are raised with the same strength (parallel regime).
Further, confined to the low-storage setting (i.e., far from the spin glass
limit), the presence of a teacher neither alters the multitasking performances
nor changes the thresholds for learning: the latter are the same whatever the
training protocol is supervised or unsupervised. Results obtained through
statistical mechanics, signal-to-noise technique and Monte Carlo simulations
are overall in perfect agreement and carry interesting insights on multiple
learning at once: for instance, whenever the cost-function of the model is
minimized in parallel on several patterns (in its description via Statistical
Mechanics), the same happens to the standard sum-squared error Loss function
(typically used in Machine Learning)
Replica Symmetry Breaking in Dense Hebbian Neural Networks
No full textUnderstanding the glassy nature of neural networks is pivotal both for theoretical and computational advances in Machine Learning and Theoretical Artificial Intelligence. Keeping the focus on dense associative Hebbian neural networks (i.e. Hopfield networks with polynomial interactions of even degree P> 2), the purpose of this paper is twofold: at first we develop rigorous mathematical approaches to address properly a statistical mechanical picture of the phenomenon of replica symmetry breaking (RSB) in these networks, then—deepening results stemmed via these routes—we aim to inspect the glassiness that they hide. In particular, regarding the methodology, we provide two techniques: the former (closer to mathematical physics in spirit) is an adaptation of the transport PDE to this case, while the latter (more probabilistic in its nature) is an extension of Guerra’s interpolation breakthrough. Beyond coherence among the results, either in replica symmetric and in the one-step replica symmetry breaking level of description, we prove the Gardner’s picture (heuristically achieved through the replica trick) and we identify the maximal storage capacity by a ground-state analysis in the Baldi-Venkatesh high-storage regime. In the second part of the paper we investigate the glassy structure of these networks: at difference with the replica symmetric scenario (RS), RSB actually stabilizes the spin-glass phase. We report huge differences w.r.t. the standard pairwise Hopfield limit: in particular, it is known that it is possible to express the free energy of the Hopfield neural network (and, in a cascade fashion, all its properties) as a linear combination of the free energies of a hard spin glass (i.e. the Sherrington–Kirkpatrick model) and a soft spin glass (the Gaussian or ”spherical” model). While this continues to hold also in the first step of RSB for the Hopfield model, this is no longer true when interactions are more than pairwise (whatever the level of description, RS or RSB). For dense networks solely the free energy of the hard spin glass survives. As the Sherrington–Kirkpatrick spin glass is full-RSB (i.e. Parisi theory holds for that model), while the Gaussian spin-glass is replica symmetric, these different representation theorems prove a huge diversity in the underlying glassiness of associative neural networks
Dense Hebbian neural networks: A replica symmetric picture of unsupervised learning
No full textWe consider dense, associative neural-networks trained with no supervision and we investigate their computational capabilities analytically, via statistical-mechanics tools, and numerically, via Monte Carlo simulations. In particular, we obtain a phase diagram summarizing their performance as a function of the control parameters (e.g. quality and quantity of the training dataset, network storage, noise) that is valid in the limit of large network size and structureless datasets. Moreover, we establish a bridge between macroscopic observables standardly used in statistical mechanics and loss functions typically used in the machine learning.
As technical remarks, from the analytical side, we extend Guerra’s interpolation to tackle the non-Gaussian distributions involved in the post-synaptic potentials while, from the computational counterpart, we insert Plefka’s approximation in the Monte Carlo scheme, to speed up the evaluation of the synaptic tensor, overall obtaining a novel and broad approach to investigate unsupervised learning in neural networks, beyond the shallow limit
HIGH FREE AND GLYCOCONJUGATED AND LOW TAUROCONJUGATED BA LEVELS IN SERUM ARE THE MIRROR OF INTESTINAL EVENTS AND HEPATIC UPTAKE
No full textFasting serum bile acid (BA) composition in healthy people is still
unknown: only recently an adequate technology to measure in the same sample both free and conjugated BAs has been developed. Aim of this study was to evaluate serum BA levels and composition in healthy subjects. Methods: 30 healthy young subjects (15 females and 15 males) [no gallstone disease, no abnormal liver tests, no liver steatosis on ultrasonography; mean age 26.5±0.8 (range 22−40 yrs)] were selected. A blood sample was taken in the morning after a standardized overnight fasting period (8 hours). Serum samples, diluted 1:6 (v/v) with NaOH 0.1N and heated to 64oC for 30 minute, were loaded on conditioned cartridge and
washed with 10 ml of water. The cartridge was eluted with 5 ml of methyl alcohol; the eluate was dried under vacuum and then reconstituted with the mobile phase (70:30 v/v ammonium acetate buffer/acetonitrile) and injected into HPLC-ESI-MS instrument. The recovery of each BA ranged from 80% to 96% and accordingly corrected.
Results: Total serum BA levels were 3.65±0.40 mmol/L (male:4.2±0.7; female:3.1±0.4 mmol/L, p = ns); total cholate levels were 0.65±0.11 mmol/L (M:0.79±0.18; F: 0.52±0.13 mmol/L, p = ns); total chenodeoxycholate levels were 1.7±0.2 mmol/L (M: 2.0±0.32; F: 1.4±0.24 mmol/L, p = ns); total deoxycholate levels were 0.8±0.13 mmol/L (M: 0.9±0.24; F: 0.72±0.10 mmol/L, p = ns); total lithocholate levels were below the detectability threshold; total ursodeoxycholate levels were 0.51±0.03 mmol/L (M: 0.55±0.051; F: 0.50±0.05 mmol/L, p = ns). Free BA levels were 1.9±0.3 mmol/L (male: 2.4±0.5; female: 1.4±0.19 mmol/L, p = ns); total glycoconjugate levels were 1.5±0.14 mmol/L (M: 1.7±0.18; F: 1.32±0.22 mmol/L, p = ns); total tauroconjugate levels were 0.29±0.05 mmol/L (M: 0.17±0.03; F: 0.41±0.09 mmol/L,
p = 0.02). Conclusions: Free and glycoconjugated BAs undergo passive diffusion and facilitated transport along the entire small intestine, accounting for their higher fractional serum level. Tauroconjugated BAs absorption occurs only in the distal ileum through an active transport system, and their hepatic uptake is extremely efficient, accounting for their lower spill into the systemic circulation; their higher levels in females suggest a pivotal role of oestrogens in the modulation of the transport systems involved in
Bas enterohepatic circulation
Lamivudine treatment for severe acute HBV hepatitis.
No full textTreatment for acute hepatitis B is recommended in order to reduce the risk of progression to fulminant hepatitis and the need of OLT. We report our experience on treatment with high dose lamivudine, in patients with severe acute HBV infection. The diagnosis was based on clinical and virological findings and exclusion of other known causes of liver damage. The decision to treat was based on the prolongation of INR together with increasing values of bilirubin and ALT. Four patients received Lamivudine 200 mg/daily until clearance of serum HBV-DNA and then 100 mg/daily until clearance of HBsAg and appearance of anti-HBs antibodies. One patient received 100 mg/daily because of chronic renal impairment. The median period of hospitalization was 13 days, and none of the patients had complications, related either to underlying disease or to therapy. The complete normalization of serum transaminases and bilirubin occurred on average after 5.5 weeks and 3 weeks respectively. All patients cleared serum HBV-DNA within three months, lost HBeAg and HBsAg and seroconverted to anti-HBe; four patients developed anti-HBs at a protective titre. Early antiviral treatment attenuates the clinical and biochemical impairment leading to fast healing and promoting complete recovery
[Executive function deficits in ADHD and Asperger syndrome]
No full textThe aim of this study is to evaluate the executive functioning of children with attention deficit hyperactivity disorder combined subtype (ADHD-C) and Asperger syndrome (AS) compared to a control group
Supervised and unsupervised protocols for hetero-associative neural networks
No full textThis paper introduces a learning framework for Three-Directional Associative Memory (TAM) models, extending the classical Hebbian paradigm to both supervised and unsupervised protocols within an hetero-associative setting. These neural networks consist of three interconnected layers of binary neurons interacting via generalized Hebbian synaptic couplings that allow learning, storage and retrieval of structured triplets of patterns. By relying upon glassy statistical mechanical techniques (mainly replica theory and Guerra interpolation), we analyze the emergent computational properties of these networks, at work with random (Rademacher) datasets and at the replica-symmetric level of description: we obtain a set of self-consistency equations for the order parameters that quantify the critical dataset sizes (i.e. their thresholds for learning) and describe the retrieval performance of these networks, highlighting the differences between supervised and unsupervised protocols. Numerical simulations validate our theoretical findings and demonstrate the robustness of the captured picture about TAMs also at work with structured datasets. In particular, this study provides insights into the cooperative interplay of layers, beyond that of the neurons within the layers, with potential implications for optimal design of artificial neural network architectures
Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
[Newspaper Clipping: Author Claims Evidence of Second JFK Assassin #1]
No full textNewspaper article titled "Author Claims Evidence of Second JFK Assassin." The article states that author Richard J. Whalen concluded "that there is circumstantial evidence to support the theory of a second assassin in the shooting of President John F. Kennedy.
- …
