Dense Hebbian neural networks: a replica symmetric picture of unsupervised learning

We consider dense, associative neural-networks trained with no supervision and we investigate their computational capabilities analytically, via a statistical-mechanics approach, and numerically, via Monte Carlo simulations. In particular, we obtain a phase diagram summarizing their performance as a function of the control parameters such as the quality and quantity of the training dataset and the network storage, 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 analytic side, we implement large deviations and stability analysis within Guerra's interpolation to tackle the not-Gaussian distributions involved in the post-synaptic potentials while, from the computational counterpart, we insert Plefka approximation in the Monte Carlo scheme, to speed up the evaluation of the synaptic tensors, overall obtaining a novel and broad approach to investigate neural networks in general

Dense Hebbian neural networks: a replica symmetric picture of supervised learning

We consider dense, associative neural-networks trained by a teacher (i.e., with supervision) and we investigate their computational capabilities analytically, via statistical-mechanics of spin glasses, and numerically, via Monte Carlo simulations. In particular, we obtain a phase diagram summarizing their performance as a function of the control parameters such as quality and quantity of the training dataset, network storage and noise, that is valid in the limit of large network size and structureless datasets: these networks may work in a ultra-storage regime (where they can handle a huge amount of patterns, if compared with shallow neural networks) or in a ultra-detection regime (where they can perform pattern recognition at prohibitive signal-to-noise ratios, if compared with shallow neural networks). Guided by the random theory as a reference framework, we also test numerically learning, storing and retrieval capabilities shown by these networks on structured datasets as MNist and Fashion MNist. As technical remarks, from the analytic side, we implement large deviations and stability analysis within Guerra's interpolation to tackle the not-Gaussian distributions involved in the post-synaptic potentials while, from the computational counterpart, we insert Plefka approximation in the Monte Carlo scheme, to speed up the evaluation of the synaptic tensors, overall obtaining a novel and broad approach to investigate supervised learning in neural networks, beyond the shallow limit, in general.Comment: arXiv admin note: text overlap with arXiv:2211.1406

The FPGA based trigger and data acquisition system for the CERN NA62 experiment

The main goal of the NA62 experiment at CERN is to measure the branching ratio of the ultra-rare K+ → π+vv decay, collecting about 100 events to test the Standard Model of Particle Physics. Readout uniformity of sub-detectors, scalability, efficient online selection and lossless high rate readout are key issues. The TDCB and TEL62 boards are the common blocks of the NA62 TDAQ system. TDCBs measure hit times from sub-detectors, TEL62s process and store them in a buffer, extracting only those requested by the trigger system following the matching of trigger primitives produced inside TEL62s themselves. During the NA62 Technical Run at the end of 2012 the TALK board has been used as prototype version of the L0 Trigger Processor

A high-resolution TDC-based board for a fully digital trigger and data acquisition system in the NA62 experiment at CERN

A Time to Digital Converter (TDC) based system, to be used for most sub-detectors in the high-flux rare-decay experiment NA62 at CERN SPS, was built as part of the NA62 fully digital Trigger and Data AcQuisition system (TDAQ), in which the TDC Board (TDCB) and a general-purpose motherboard (TEL62) will play a fundamental role. While TDCBs, housing four High Performance Time to Digital Converters (HPTDC), measure hit times from sub-detectors, the motherboard processes and stores them in a buffer, produces trigger primitives from different detectors and extracts only data related to the lowest trigger level decision, once this is taken on the basis of the trigger primitives themselves. The features of the TDCB board developed by the Pisa NA62 group are extensively discussed and performance data is presented in order to show its compliance with the experiment requirements.Comment: 6 pages, 7 figures, presented to IEEE RT 2014 Conference and I want to publish in TN

The Mu2e Crystal Calorimeter: An Overview

The Mu2e experiment at Fermilab will search for the standard model-forbidden, charged lepton flavour-violating conversion of a negative muon into an electron in the field of an aluminium nucleus. The distinctive signal signature is represented by a mono-energetic electron with an energy near the muon's rest mass. The experiment aims to improve the current single-event sensitivity by four orders of magnitude by means of a high-intensity pulsed muon beam and a high-precision tracking system. The electromagnetic calorimeter complements the tracker by providing high rejection power in muon to electron identification and a seed for track reconstruction while working in vacuum in presence of a 1 T axial magnetic field and in a harsh radiation environment. For 100 MeV electrons, the calorimeter should achieve: (a) a time resolution better than 0.5 ns, (b) an energy resolution <10%, and (c) a position resolution of 1 cm. The calorimeter design consists of two disks, each loaded with 674 undoped CsI crystals read out by two large-area arrays of UV-extended SiPMs and custom analogue and digital electronics. We describe here the status of construction for all calorimeter components and the performance measurements conducted on the large-sized prototype with electron beams and minimum ionizing particles at a cosmic ray test stand. A discussion of the calorimeter's engineering aspects and the on-going assembly is also reported

Mu2e Crystal Calorimeter Readout Electronics: Design and Characterisation

The Mu2e experiment at Fermi National Accelerator Laboratory will search for the charged-lepton flavour-violating neutrinoless conversion of negative muons into electrons in the Coulomb field of an Al nucleus. The conversion electron with a monoenergetic 104.967 MeV signature will be identified by a complementary measurement carried out by a high-resolution tracker and an electromagnetic calorimeter, improving by four orders of magnitude the current single-event sensitivity. The calorimeter—composed of 1348 pure CsI crystals arranged in two annular disks—has a high granularity, 10% energy resolution and 500 ps timing resolution for 100 MeV electrons. The readout, based on large-area UV-extended SiPMs, features a fully custom readout chain, from the analogue front-end electronics to the digitisation boards. The readout electronics design was validated for operation in vacuum and under magnetic fields. An extensive radiation hardness certification campaign certified the FEE design for doses up to 100 krad and 1012 n1MeVeq/cm2 and for single-event effects. A final vertical slice test on the final readout chain was carried out with cosmic rays on a large-scale calorimeter prototype

DESIGN AND IMPLEMENTATION OF AN INTEGRATED FULLY DIGITAL TRIGGER AND DATA ACQUISITION SYSTEM FOR HIGH ENERGY PHYSICS EXPERIMENTS

The work reported in this thesis has been performed within the project “Experiment to detect KL Very Rare decays” (KLEVER). KLEVER aims at using powerful programmable systems in the first stages of the data collection and selection process in particle experiments at accelerators, i.e. the use of hardware processors based on Field-Programmable Gate Arrays (FPGAs) and Graphic Processing Units GPUs. The FPGAs are placed at the front-end stage of detectors, immediately after digitization, thus allowing data processing at an earlier stage of the acquisition and trigger chain. We aim also to exploit the use of highly parallelized processors, the GPUs, in order to process data at early selection stages. In recent years GPUs were increasingly used to build high-performing computing systems at reasonable prices, but the growth of their computing power and the reduction of their intrinsic latency is such that they are nowadays suited for real-time application. Both these possibilities entail an effort of integration and adaptation, as these systems were developed for totally different purposes, such as the automotive and the video-games market. In particular the intention is to probe the performances of FPGAs and GPUs processors by building a system acting as an easily updatable test bench of the attainable collection and selection capabilities of large amounts of data. This will allow to evaluate the present technological limits, which in turn represent the most important bottleneck for a high-precision physics experiment studying ultra-rare decays. My work was focused on the development of the Trigger and Data Acquisition System for the experiment NA62. The NA62 experiment is placed in the CERN North Area in the Super Proton Synchrotron accelerator extraction site and it aims at measuring the Branching Ratio of the ultra-rare decay in order to provide a stringent test of the Standard Model. Since the value predicted by the Standard Model is very precise, the measurement of this quantity represents an excellent way to investigate the existence of New Physics, or in case of agreement with the Standard Model(SM) to improve the current knowledge of the |Vtd| parameter of the CKM matrix. The use of a high-rate kaon beam will result in an event rate of about 15 MHz, so high that it is impossible to store data on disk without a very selective reduction. The experiment use devised three trigger levels, allowing to reduce the data rate fed to the readout PC farm down to 10 kHz. High Energy Physics environment, the historical approach to Trigger and data Ac- Quisition (TDAQ) system, the state of the art and the integrated fully-digital system approach proposed in this thesis work are described in chapter 1. In chapter 2 the NA62 experimental setup is described, composed of an upstream part, with detectors used to identify and measure the propriety of the K+ inside the beam, and a downstream part where the decay products are detected. The first part of this work concerns the hardware and firmware development of the common trigger and data acquisition system for the majority of detectors in NA62. The unified trigger and data acquisition system, where the trigger is integrated inside the DAQ, and allowing a good control of the trigger using the same data available at readout, and a excellent flexibility, is presented in chapter 3. The second part of the work describes the NA62 L0 standard trigger and the studies performed for a L0 trigger based on GPU. The L0 hardware trigger is described in chapter 4 and the attention is focused on the trigger firmware developed for the RICH detector. The use of GPU in high energy physics, the NA62 GPU trigger and the GPURICH firmware are described in chapter 5. Il lavoro riportato in questa tesi è stata eseguito nell’ambito del progetto "Experiment to detect KL Very Rare decays "(KLEVER).Obiettivo di KLEVER sono lo studio e la realizzazione di sistemi integrati per l’elaborazione dei dati acquisiti da esperimenti di fisica delle alte energie, basati su processori massicciamente paralleli; KLEVER si propone di esplorare le possibilita‘ attuali offerte dai processori implementabili in FPGA e dai processori grafici (GPU). Le FPGA sono posizionate vicino ai front end dei rivelatori e ricevono quindi i dati digitalizzati da usare nella selezione degli eventi gia’ negli stadi piu’ a monte della catena di acquisizione. Le GPU sono processori molto avanzati utilizzati nelle schede grafiche ed negli ultimi anni vengono utilizzati in modo sempre piu’ massiccio anche per realizzare sistemi di calcolo di grande potenza a costi contenuti. La crescita continua della loro potenza e la diminuzione dei tempi di latenza permette oggi di considerare tali processori anche per possibili applicazioni in tempo reale negli esperimenti di Fisica delle particelle agli acceleratori. Entrambe queste possibilità comportano uno sforzo di integrazione e adattamento, in quanto questi sistemi sono stati sviluppati per impieghi totalmente diversi, come ad esempio nell’industria automobilistica e nel mercato videogiochi. In particolare si intende sondare le prestazioni dei processori FPGA e GPU costruendo un sistema che agisca come un banco di prova facilmente aggiornabile delle capacità di raccolta e selezione raggiungibili di grandi quantità di dati. Ciò consentirà di impostare gli attuali limiti tecnologici, che a loro volta rappresentano più importante collo di bottiglia per un esperimento di fisica ad alta precisione determinato a studiare decadimenti ultra rari. Il mio lavoro si è concentrato sullo sviluppo del trigger e del sistema di acquisizione dati per l’esperimento NA62. L’esperimento NA62 è collocato nella North Area del CERN sul sito di estrazione dell’acceleratore Super Proton Synchroton e ha lo scopo di misurare il Branching Ratio del decadimento ultra raro per fornire una prova rigorosa del Modello standard. Dal momento che il valore previsto dal modello standard è molto preciso, la misura di questa quantità rappresenta un ottimo modo per indagare l’esistenza di nuova fisica, o in caso di accordo con il Modello Standard (SM) per migliorare le attuali conoscenze del parametro |Vtd| della matrice CKM. L’uso di un fascio ad alta intensità si traduce in un rate di eventi di circa 15 MHz, valore talmente elevato che rende impossibile la memorizzazione dei dati su disco senza una riduzione molto selettiva. Tre livelli di trigger sono stati realizzati in modo tale da ridurre a 10 KHz il rate di dati da inviare alla PC farm. Una introduzione sul mondo della fisica delle alte energie, un cenno a come si sono evoluti i sistemi di trigger e acquisizione dati, una panoramica sullo stato dell’arte e una introduzione al sistema integrato di trigger e acquisizione dati completamente digitale proposto sono descritti nel capitolo 1. Nel capitolo 2 viene descritto l’apparato sperimentale di NA62, composto da una parte a monte per la identificazione e la misura del K+ nel fascio e una parte a valle dove vengono identificati i prodotti del decadimento. La prima parte del mio lavoro riguarda il progetto e la realizzazione dell’ hardware del sistema di trigger e acquisizione dati comune per la maggior parte dei rivelatori in NA62 e lo sviluppo del firmware ad esso associato. Il sistema integrato di trigger e acquisizione dati , in cui il trigger può utilizzare tutti i dati digitalizzati, è presentato nel capitolo 3. La seconda parte del mio lavoro descrive il trigger standard di Livello 0 (L0) di NA62 e gli studi eseguiti per realizzare un trigger innovativo di livello 0 basato sulle GPU. Il trigger standard L0 è descritto nel capitolo 4. Nello stesso capitolo viene descritto ampiamente il firmware di trigger sviluppato per il rivelatore RICH. L’utilizzo delle GPU in fisica delle alte energie, il trigger basato sulle GPU in NA62 e il firmware GPU-RICH sono descritti nel capitolo 5

Può la dialisi dinamica essere considerata un metodo attendibile per studiare il rilascio di farmaci da sistemi nanoparticellari?

Scopo del lavoro: Gli studi riportati in letteratura sulla cinetica di rilascio in vitro di farmaci da nanoparticelle sono stati effettuati in modo acritico, prevalentemente utilizzando il metodo della dialisi dinamica. L’obiettivo di questa tesi è valutare la reale pertinenza dei dati di dialisi con il rilascio del farmaco da sistemi nanoparticellari. Metodi: A scopo esemplificativo sono state usate nanoparticelle a base di chitosano medicate con diclofenac (DCF) o ofloxacina (OFX). Le nanoparticelle sono state preparate per reticolazione ionotropica con tripolifosfato e caratterizzate per dimensioni ed efficienza di incapsulamento. Per ciascun farmaco, è stata effettuata la dialisi dinamica della dispersione di nanoparticelle, della soluzione contenente chitosano cloridrato (ChHCl) disciolto e della soluzione del solo farmaco. Inoltre sono stati fatti esperimenti in cui a predeterminati intervalli di tempo la dialisi veniva interrotta per determinare la concentrazione del farmaco nella fase ricevente, nella matrice nanoparticellare e nel mezzo di dispersione delle nanoparticelle e da qui costruire la cinetica del farmaco nelle tre fasi. Il rilascio di ciascun farmaco dalle nanoparticelle è stato determinato anche con il metodo della ultracentrifugazione. La dispersione nanoparticellare veniva mantenuta sotto agitazione a 37°C e ad intervalli di tempo prestabiliti ne veniva prelevata un’aliquota che veniva analizzata per il farmaco dopo ultracentrifugazione. Risultati: Sebbene i dati relativi alla cinetica del farmaco nella fase ricevente possano essere interpretati in termini di rilascio sostenuto dalle nanoparticelle, i dati della cinetica del farmaco nella matrice nanoparticellare e nel mezzo di dispersione mostrano che, con entrambi i farmaci, il processo è in realtà controllato dalla permeazione del farmaco attraverso la membrana da dialisi. L’analisi dei dati relativi alla cinetica del farmaco nella fase ricevente rivela un’interazione reversibile del DCF con la superficie delle nanoparticelle disperse, simile all’interazione di questo farmaco con il ChHCl disciolto. Questo tipo di interazione non è stata osservata con OFX. I risultati ottenuti con il metodo dell’ultracentrifugazione sono in accordo con questa interpretazione dei dati di dialisi. Conclusioni: Gli esempi studiati in questa tesi mostrano che i dati di dialisi dinamica ottenuti da una dispersione nanoparticellare non sono necessariamente descrittivi del rilascio sostenuto del farmaco dalle nanoparticelle, quindi, se interpretati in modo acritico, possono essere fuorvianti

The TEL62: A real-time board for the NA62 Trigger and Data AcQuisition. Data flow and firmware design

The main goal of the NA62 experiment at CERN SPS is to measure the branching ratio of the ultra-rare K+→π+νν decay, collecting about 100 events in two years of data taking to test the Standard Model of Particle Physics. Readout uniformity of sub-detectors, scalability, efficient online selection and lossless high rate readout are key issues. The TEL62 boards are the common blocks of the NA62 Trigger and Data AcQuisition (TDAQ) system. TEL62s process and store hits coming from the subdetectors in a buffer according to their timestamp, extracting only those requested by the trigger system, which merges trigger primitives also produced by TEL62s. The complete dataflow and firmware organization are described