Phase-Change Memory in Neural Network Layers with Measurements-based Device Models

The search for energy efficient circuital implementations of neural networks has led to the exploration of phase-change memory (PCM) devices as their synaptic element, with the advantage of compact size and compatibility with CMOS fabrication technologies. In this work, we describe a methodology that, starting from measurements performed on a set of real PCM devices, enables the training of a neural network. The core of the procedure is the creation of a computational model, sufficiently general to include the effect of unwanted non-idealities, such as the voltage dependence of the conductances and the presence of surrounding circuitry. Results show that, depending on the task at hand, a different level of accuracy is required in the PCM model applied at train-time to match the performance of a traditional, reference network. Moreover, the trained networks are robust to the perturbation of the weight values, up to 10% standard deviation, with performance losses within 3.5% for the accuracy in the classification task being considered and an increase of the regression RMS error by 0.014 in a second task. The considered perturbation is compatible with the performance of state-of-the-art PCM programming techniques

Podolian cattle: reproductive activity, milk and future prospects

In the present study, an original article about Podolian cattle and its milk was performed. In detail, the following factors on reproductive career of Podolian cattle in semi-extensive and extensive rearing were analysed: age of calving, gestation lenght, calving interval length, abortions percentage, conception and calving period. Chemical and phisycal parameters (protein, fat and lactose), somatic cell count, lisozyme content and antiradical activity, with ABTS and DPPH assays, of Podolian milk in semiextensive and extensive rearing were evaluated. Finally, suggestions on future prospects of Podolian milk use were proposed: the preparation of hand soap with 5 percentage of podolian milk and the potential role of this breed for prevention and propagation of fire. The data concerning the reproductive career, milk and envinromental role of 677 cows registered in the Herdbook were analysed. The results showed that the 58.56% of the cows manifested a calving interval of 11-14 months. The reproductive activity occurred in spring; over 70% of the cows calved in the period February-April. The chemical-physical aspects of milk are in agreement with literature. It presents an high antioxidant activity values for each group (97.03% and 97.50% for ABTS and 52.09% and 52.60% for DPPH, semiextensive and extensive system respectively). The consumer test shows that the subjects appreciated the soap containing 5% of Podolian milk for different aspect. The data about environmental role were obtained from Podolian cows reared in fifteen grazing areas were monitored for five years during the summer pasture, when the Podolian cattle graze on green grazing areas located in Basilicata region (South of Italy). Therefore, an efficient management of grazing by Podolian cattle could be an important tool to prevent the fire propagation

Combined HW/SW Drift and Variability Mitigation for PCM-based Analog In-memory Computing for Neural Network Applications

Matrix-Vector Multiplications (MVMs) represent a heavy workload for both training and inference in Deep Neural Networks (DNNs) applications. Analog In-memory Computing (AIMC) systems based on Phase Change Memory (PCM) has been shown to be a valid competitor to enhance the energy efficiency of DNN accelerators. Although DNNs are quite resilient to computation inaccuracies, PCM non-idealities could strongly affect MVM operations precision, and thus the accuracy of DNNs. In this paper, a combined hardware and software solution to mitigate the impact of PCM non-idealities is presented. The drift of PCM cells conductance is compensated at the circuit level through the introduction of a conductance ratio at the core of the MVM computation. A model of the behaviour of PCM cells is employed to develop a device-aware training for DNNs and the accuracy is estimated in a CIFAR-10 classification task. This work is supported by a PCM-based AIMC prototype, designed in a 90-nm STMicroelectronics technology, and conceived to perform Multiply-and-Accumulate (MAC) computations, which are the kernel of MVMs. Results show that the MAC computation accuracy is around 95% even under the effect of cells drift. The use of a device-aware DNN training makes the networks less sensitive to weight variability, with a 15% increase in classification accuracy over a conventionally-trained Lenet-5 DNN, and a 36% gain when drift compensation is applied

Decoding Algorithms and HW Strategies to Mitigate Uncertainties in a PCM-Based Analog Encoder for Compressed Sensing

Analog In-Memory computing (AIMC) is a novel paradigm looking for solutions to prevent the unnecessary transfer of data by distributing computation within memory elements. One such operation is matrix-vector multiplication (MVM), a workhorse of many fields ranging from linear regression to Deep Learning. The same concept can be readily applied to the encoding stage in Compressed Sensing (CS) systems, where an MVM operation maps input signals into compressed measurements. With a focus on an encoder built on top of a Phase-Change Memory (PCM) AIMC platform, the effects of device non-idealities, namely programming spread and drift over time, are observed in terms of the reconstruction quality obtained for synthetic signals, sparse in the Discrete Cosine Transform (DCT) domain. PCM devices are simulated using statistical models summarizing the properties experimentally observed in an AIMC prototype, designed in a 90 nm STMicroelectronics technology. Different families of decoders are tested, and tradeoffs in terms of encoding energy are analyzed. Furthermore, the benefits of a hardware drift compensation strategy are also observed, highlighting its necessity to prevent the need for a complete reprogramming of the entire analog array. The results show >30 dB average reconstruction quality for mid-range conductances and a suitably selected decoder right after programming. Additionally, the hardware drift compensation strategy enables robust performance even when different drift conditions are tested

La zoocosmesi: nuova opportunità per l'allevamento bovino podolico.

Il latte di bovine podoliche, allevate su pascoli naturali di montagna non trattati con diserbanti e fertilizzanti chimici, rappresenta un ottimo costituente di base per la preparazione di cosmetici naturali essendo un tensore naturale, ricco in vitamine, sali minerali, antiossidanti, proteine, enzimi e lipidi, essenziali per la protezione e rigenerazione delle cellule. Nell’ambito di una più ampia ricerca inerente alla "Zoocosmesi per le imprese e l'innovazione di prodotto" si è svolta una prima indagine di mercato finalizzata alla valutazione della propensione all'acquisto di un nuovo prodotto cosmetico a base di latte podolico. L'indagine è stata condotta su un gruppo di 400 consumatori residenti in Basilicata, ai quali è stato somministrato un questionario semi-strutturato. I risultati hanno evidenziato che l’84% degli intervistati è disposta ad acquistare un prodotto definito "di nuova generazione" e il 69% evidenzia una propensione per prodotti innovativi a base di sostanze naturali

Longitudinal study on low-dose aspirin versus placebo administration in silent brain infarcts: the silence study

Background. We investigated low-dose aspirin (ASA) efficacy and safety in subjects with silent brain infarcts (SBIs) in preventing new cerebrovascular (CVD) events as well as cognitive impairment. Methods. We included subjects aged ≥45 years, with at least one SBI and no previous CVD. Subjects were followed up to 4 years assessing CVD and SBI incidence as primary endpoint and as secondary endpoints: (a) cardiovascular and adverse events and (b) cognitive impairment. Results. Thirty-six subjects received ASA while 47 were untreated. Primary endpoint occurred in 9 controls (19.1%) versus 2 (5.6%) in the ASA group (p=0.10). Secondary endpoints did not differ in the two groups. Only baseline leukoaraiosis predicts primary [OR 5.4 (95%CI 1.3-22.9, p=0.022)] and secondary endpoint-A [3.2 (95%CI 1.1-9.6, p=0.040)] occurrence. Conclusions. These data show an increase of new CVD events in the untreated group. Despite the study limitations, SBI seems to be a negative prognostic factor and ASA preventive treatment might improve SBI prognosis. EU Clinical trial is registered with EudraCT Number: 2005-000996-16; Sponsor Protocol Number: 694/30.06.04

Omecamtiv mecarbil in chronic heart failure with reduced ejection fraction, GALACTIC‐HF: baseline characteristics and comparison with contemporary clinical trials

Aims: The safety and efficacy of the novel selective cardiac myosin activator, omecamtiv mecarbil, in patients with heart failure with reduced ejection fraction (HFrEF) is tested in the Global Approach to Lowering Adverse Cardiac outcomes Through Improving Contractility in Heart Failure (GALACTIC‐HF) trial. Here we describe the baseline characteristics of participants in GALACTIC‐HF and how these compare with other contemporary trials. Methods and Results: Adults with established HFrEF, New York Heart Association functional class (NYHA) ≥ II, EF ≤35%, elevated natriuretic peptides and either current hospitalization for HF or history of hospitalization/ emergency department visit for HF within a year were randomized to either placebo or omecamtiv mecarbil (pharmacokinetic‐guided dosing: 25, 37.5 or 50 mg bid). 8256 patients [male (79%), non‐white (22%), mean age 65 years] were enrolled with a mean EF 27%, ischemic etiology in 54%, NYHA II 53% and III/IV 47%, and median NT‐proBNP 1971 pg/mL. HF therapies at baseline were among the most effectively employed in contemporary HF trials. GALACTIC‐HF randomized patients representative of recent HF registries and trials with substantial numbers of patients also having characteristics understudied in previous trials including more from North America (n = 1386), enrolled as inpatients (n = 2084), systolic blood pressure < 100 mmHg (n = 1127), estimated glomerular filtration rate < 30 mL/min/1.73 m2 (n = 528), and treated with sacubitril‐valsartan at baseline (n = 1594). Conclusions: GALACTIC‐HF enrolled a well‐treated, high‐risk population from both inpatient and outpatient settings, which will provide a definitive evaluation of the efficacy and safety of this novel therapy, as well as informing its potential future implementation

Large-scale Network Analysis on Distributed Architectures

Questa dissertazione esamina le sfide e i limiti che gli algoritmi di analisi di grafi incontrano in architetture distribuite costituite da personal computer. In particolare, analizza il comportamento dell'algoritmo del PageRank così come implementato in una popolare libreria C++ di analisi di grafi distribuiti, la Parallel Boost Graph Library (Parallel BGL). I risultati qui presentati mostrano che il modello di programmazione parallela Bulk Synchronous Parallel è inadatto all'implementazione efficiente del PageRank su cluster costituiti da personal computer. L'implementazione analizzata ha infatti evidenziato una scalabilità negativa, il tempo di esecuzione dell'algoritmo aumenta linearmente in funzione del numero di processori. Questi risultati sono stati ottenuti lanciando l'algoritmo del PageRank della Parallel BGL su un cluster di 43 PC dual-core con 2GB di RAM l'uno, usando diversi grafi scelti in modo da facilitare l'identificazione delle variabili che influenzano la scalabilità. Grafi rappresentanti modelli diversi hanno dato risultati differenti, mostrando che c'è una relazione tra il coefficiente di clustering e l'inclinazione della retta che rappresenta il tempo in funzione del numero di processori. Ad esempio, i grafi Erdős–Rényi, aventi un basso coefficiente di clustering, hanno rappresentato il caso peggiore nei test del PageRank, mentre i grafi Small-World, aventi un alto coefficiente di clustering, hanno rappresentato il caso migliore. Anche le dimensioni del grafo hanno mostrato un'influenza sul tempo di esecuzione particolarmente interessante. Infatti, si è mostrato che la relazione tra il numero di nodi e il numero di archi determina il tempo totale

LA NARRATIVA DI ALESSANDRO BONSANTI. (ITALIAN TEXT)

The aim of this study is to give an unpretentious and straightforward account of the place that Bonsanti occupies in twentieth century Italian literature. The reader who wants to know about Bonsanti and his works will find enough in this dissertation to bring himself up to date on critical estimates. The works of Bonsanti cover a period of fifty years, from his tentative beginning as a short story writer to his maturity as a capable novelist and playwright.^ Under the direction of his parents he attended Engineering School, but his studies were precluded due to financial difficulties. Finding himself in need of work, he moved to Milan, where he was hired as a bank clerk. He remained in this activity for three years, but we can not say that he found satisfaction in his work. His passion was literature. Bonsanti read Italian, European, and American authors, and he also showed profound interest in literary magazines such as La Ronda, Novecento, and Il Baretti. Immediately after the Milanese sojourn, Bonsanti moved back to Florence where he made contact with some of the leading figures of the antifascist movement. Together with Alberto Carocci he founded Solaria. Bonsanti\u27s early affiliation with important names in the literary world gave him a privileged start. Meanwhile, his first narrative attempts had begun. Already in 1928, while he was still in Milan, he had published in Fiera Letteraria his first short story, Briganti in Maremma.^ His early fiction is comprised mostly of short stories set in the historic-social climate of the early nineteenth century. Topics, characters, and actions are contemplated with detachment, the author looking from afar on the background of a lyrically delineated landscape that frames the long and frequent reflective monologues of the protagonists.^ With few variations one can find the same characteristics in subsequent works: Racconto militare, 1937; Introduzione al gran viaggio, 1940; La vipera e il toro, 1955; I cavalli di bronzo, 1956; Racconti lontani, 1962; La buca di San Colombano, 1964; La nuova stazione di Firenze, 1965; and two plays, Occtaviano and Don Giovanni under one title: Teatro domestico, 1970. One of the main differences rests in the fact that these later works reflect the period of the Solaria experience (1926-1934).^ Bonsanti\u27s style seems to link with the tradition of the nineteenth century novel in the Manzonian manner. He connects to Manzoni because of his polished style and perfection of language. The author finds the meaning of life in the revelatory gestures of the subconscious. He alternates or mixes the introspective methods dear to Proust with a deductive and moralizing vein. In his works, next to cherishing the idyllic evasion, Bonsanti becomes the acute investigator of character and mores. These tasks are achieved by introducing the prominent theme: memory. The psychological investigation seems to be marginal compared with the action of the novels, but in reality it constitutes the main structure.^ Given to the narrative of memory, the life of the character develops and concludes itself in an indefinite gamut of personal considerations, of passional and unbecoming motions, of turbulent feelings, and of impulses and particular solicitations. At times this intimacy is projected in environments dating back to the early nineteenth century, where the countryside becomes an integral part of the action and the feelings of the characters; at later times, starting with La buca di San Colombano the theme of remembrance is truly personified and it becomes the ragion d\u27essere of the author. Bonsanti\u27s observations seem to always have something new to add, giving more fulfillment to the portrait, and further depth to the introspection of the psyche.