86,653 research outputs found
Vanishing of the p-part of the Shafarevich-Tate group of a modular form and its consequences for Anticyclotomic Iwasawa Theory
No full textIn questa tesi dimostriamo una generalizzazione, per il twist autoduale della rappresentazione associata ad una forma modulare di peso , di un recente risultato A. Matar, J. Nekovar, “Kolyvagin’s result on the vanishing of \sha(E/K)[p^\infty] and its consequences for anticyclotomic Iwasawa theory”, in: J. Théor. Nombres Bordeaux 31.2 (2019), in teoria di Iwasawa anticiclotomica per curve ellittiche.
Più precisamente diamo una definizione della (-parte dei) gruppi di Shafarevich-Tate \sha_{\mathfrak{p}^\infty}(f/K) e \sha_{\mathfrak{p}^\infty}(f/K_\infty) di sopra un campo quadratico immaginario che soddifi l'ipotesi di Heegner e sopra la sua -estensione anticiclotomica e mostriamo che se il ciclo di Heegner generalizzato di base non è di torsione e non è divisibile per , allora \sha_{\mathfrak{p}^\infty}(f/K) = \sha_{\mathfrak{p}^\infty}(f/K_\infty) = 0; inoltre il duale di Pontryagin del gruppo di Selmer di Bloch-Kato della rappresentazione , dove è il reticolo -stabile dentro costruito da Nekovar in “Kolyvagin’s method for Chow groups of Kuga-Sato varieties”, in: Invent. Math.n 107.1 (1992), è libero di rango sull'algebra di Iwasawa.In this thesis we prove a generalization, for the self-dual twist of the representation attached to a modular forms of even weight , of a recent result of A. Matar, J. Nekovar, “Kolyvagin’s result on the vanishing of \sha(E/K)[p^\infty] and its consequences for anticyclotomic Iwasawa theory”, in: J. Théor. Nombres Bordeaux 31.2 (2019), in the anticyclotomic Iwasawa Theory for elliptic curves.
More precisely we give a definition for the (-part of the) Shafarevich-Tate groups \sha_{\mathfrak{p}^\infty}(f/K) and \sha_{\mathfrak{p}^\infty}(f/K_\infty) of over an imaginary quadratic field satisfying the Heegner hypothesis and over its anticyclotomic -extension and we show that if the basic generalized Heegner cycle is non-torsion and not divisible by , then \sha_{\mathfrak{p}^\infty}(f/K) = \sha_{\mathfrak{p}^\infty}(f/K_\infty) = 0; moreover the Pontryagin dual of the Bloch-Kato Selmer group of the representation , where is the -stable lattice inside constructed by Nekovar in “Kolyvagin’s method for Chow groups of Kuga-Sato varieties”, in: Invent. Math.n 107.1 (1992), is free of rank over the Iwasawa algebra
: A Novel Analog Model Mimicking Megathrust Seismic Cycles
No full textIn the last decades, seismotectonic analog models have been developed to better understand many aspects of the seismic cycle. Differently from other lab-quake experiments, seismotectonic models mimic the first order characteristics of the seismic cycle in a scaled fashion. Here we introduce Foamquake: a novel seismotectonic model with a granular frictional interface that as a whole behaves elastoplastically. The model experiences cycles of elastic loading and release via spontaneous nucleation of frictional instabilities at the base of an elastic foam wedge, hereafter called foamquakes. These analog earthquakes show source parameters (i.e., moment-duration and moment-rupture area) scaling as great interplate earthquakes and a coseismic displacement of few tens of meters when scaled to nature. Models with two asperities separated by a barrier can be performed with Foamquake given the 3D nature of the setup. Such model configuration generates sequences of full and partial ruptures with different recurrence intervals as well as rupture cascades. By tuning the normal load acting on individual asperities, Foamquake reproduces superimposed cycles rupture patterns such as those observed along natural megathrusts. The physical properties of asperities and barriers affect model seismic behavior. Asperities with similar properties and low yield strength fail preferentially in a simultaneous manner. The combination of all those characteristics suggests that Foamquake is a valuable tool for investigating megathrust seismicity and seismic processes that depend on the 3D nature of the subduction environment
Forecasting Surface Velocity Fields Associated With Laboratory Seismic Cycles Using Deep Learning
No full textAbstract It has been recently demonstrated that Machine Learning (ML) can predict laboratory earthquakes. Here we propose a prediction framework that allows forecasting future surface velocity fields from past ones for analog experiments of megathrust seismic cycles. Using data from two types of experiments, we explore the prediction performances of multiple Deep Learning (DL) and ML algorithms. In such a self-supervised regression, no feature extraction is required and the entire seismic cycle is forecasted. The onset, magnitude, and propagation of analog earthquakes can thus be predicted at different prediction horizons. From all architectures tested in this study, convolutional recurrent neural networks (CNN-LSTM and CONVLSTM) provide the best predictions although their performances depend on experiment characteristics and hyperparameters tuning. Analog earthquakes can be successfully anticipated up to a horizon of the order of their duration. This laboratory-based study may open new avenues for transfer learning applications with data from natural subduction zones
Tunneling-based CMOS Floating Gate Synapse for Low Power Spike Timing Dependent Plasticity
No full textWe propose a CMOS architecture for spiking neural networks with permanent memory and online learning. It uses a three-transistors synapse with a floating node that stores the synaptic weight, programmed by using only Fowler-Nordheim tunneling current in the pA range for ultra-low power operation. A neuron with a conditioning circuit programs the floating gate synapse following the spike timing dependent plasticity rule. Simulations using a standard 150 nm CMOS process show the online learning capabilities of the architecture
An evaluation of an enzyme immunoassay method for immunoreactive trypsin in dried blood spots
No full textA novel monoclonal antibody based enzyme immunoassay (EIA) method for the measurement of the human cationic trypsinogen (NeoScreen, AGEN Biomedical Ltd., Acacia Ridge, Australia) in dried blood spots for the neonatal screening of cystic fibrosis was evaluated. The calibration standards provided as dried blood spots by AGEN are highly unstable and must be replaced with user prepared materials. Reference values from control individuals were obtained by parametric methods. A preliminary comparison with a polyclonal antibody based RIA method (Trypsik, SORIN Biomedica, Saluggia, Italy) was performed. Regression analysis between the RIA and the EIA methods gave a coefficient of correlation of 0.58 for RIA values < 40 •g/L and of 0.77 for RIA values ≥ 40 •g/L. Average CV of the within-run imprecision for the EIA method was 19.6% and for the RIA method 28.8%. CVs of the between-run imprecision at low, intermediate and high values for the EIA method were 23.7%, 15.8%, 15.6% and for the RIA method 20.6%, 14.4%, 11.2%. The diagnostic accuracy analyzed by a Receiver Operating Characteristics (ROC) curve of the RIA method gave a maximum accuracy of 190.9 while that of a simulated ROC curve for the EIA method was 193.0. We found that the precision and the diagnostic accuracy of the EIA method (AGEN) are equal to or better than those of one of the RIA methods
Tunneling-based CMOS Floating Gate Synapse for Low Power Spike Timing Dependent Plasticity
No full textWe propose a CMOS architecture for spiking neural networks with permanent memory and online learning. It uses a three-transistors synapse with a floating node that stores the synaptic weight, programmed by using only Fowler-Nordheim tunneling current in the pA range for ultra-low power operation. A neuron with a conditioning circuit programs the floating gate synapse following the spike timing dependent plasticity rule. Simulations using a standard 150 nm CMOS process show the online learning capabilities of the architecture
CyberKnife®; Imaging-dose evaluation during IGRT-SRSand IGRT-SBRT treatments
No full textIl sistema di radiochirurgia robotica CyberKnife® è utilizzato per trattamenti di radoiochirurgia e radioterapia stereotassica intra ed extracranica guidati dalle immagini (IGRT). I trattamenti di tumori localizzati vengono erogati in singole (radiochirurgia stereotassica SRS[8]) o poche sedute (radioterapia stereotassica SBRT[11]) con un’elevata dose di radiazioni ionizzanti. Per questa ragione è necessaria un’elevata accuratezza nella localizzazione del bersaglio, ottenuta con il sistema di imaging (TLS).
Il TLS consiste di due sorgenti ortogonali di raggi X diagnostici fissate al soffitto orientati verso due rivelatori integrati nel pavimento. Tale sistema richiede l’acquisizione di numerose coppie di radiografie allo scopo di localizzare la posizione del bersaglio. Tali immagini vengono effettuate con frequenza e dati espositivi decisi dal TSRM, per tutta la durata del trattamento.
Scopo di questo studio è la determinazione dell’Air Kerma relativo al TLS del sistema CyberKnife® presente presso l’Istituto Europeo di Oncologia (Milano – Italia) ed una valutazione della dose imaging-dipendente su una popolazione clinica di pazienti sottoposti a trattamenti radioterapici con CyberKnife®.
Tutte le misure sono state effettuate con una camera a ionizzazione posta al centro dell’imaging della sala di trattamento di CyberKnife®, nel punto di intersezione degli assi principali dei due fasci di raggi X. La camera è stata connessa ad un elettrometro e tutte le letture sono state corrette per condizioni ambientali (pressione atmosferica e temperatura della stanza) e per la costante di calibrazione. Sono stati ottenuti i valori di Air Kerma variando i parametri espositivi del sistema di imaging di CyberKnife® (differenza di potenziale e carica elettrica). Questi dati hanno permesso la costruzione di un’equazione con cui è possibile stimare realisticamente la dose aggiuntiva di radiazioni dovuta all’imaging; i valori misurati ed i valori calcolati per i medesimi punti sono stati confrontati per stimare l’accuratezza della nostra equazione. È stato poi effettuato un controllo dei parametri espositivi di un campione di popolazione clinica trattato presso il nostro centro per il quale abbiamo calcolato i valori di Air Kerma. Questi valori sono infine stati confrontati con i valori forniti dal software del sistema CyberKnife®.
I valori di Air Kerma da noi calcolati hanno mostrato, in media, una variazione pari a ±1.8%, con un massimo del ±4.4% quando confrontati con i valori misurati di Air Kerma. Infine l’analisi dei valori di Air Kerma del campione clinico ha mostrato una sottostima della dose dovuta all’imaging da parte del software del sistema CyberKnife® quando paragonata con la dose calcolata da noi.
L’Air Kerma dipende dai valori di differenza di potenziale e carica elettrica selezionati dal TSRM e dal numero complessivo di coppie di radiografie necessarie per un trattamento completo di SRS o SBRT.
La localizzazione di bersagli con il sistema 6D Skull richiede, in genere, un numero inferiore di immagini e valori inferiori di differenza di potenziale e carica elettrica rispetto a trattamenti con X-Sight Spine, tutto ciò porta ad una più bassa dose dovuta all’imaging per pazienti trattati con il sistema 6D Skull. In media, la dose aggiuntiva dovuta all’imaging per il nostro campione è stata stimata essere lo 0.1% (per 6D Skull) e 0.3% (per X-Sight Spine) della dose terapeutica.(IGRT) intra and extracranial stereotactic radiotherapy and radiosurgery. The treatments of localized tumors are performed in a single (stereotactic radiosurgery SRS[8]) or few sessions (stereotactic radiotherapy SBRT[11]) with a high ionizing radiation rate. For this reason a high level of accuracy on target localization, obtained by the imaging guided system (TLS), is necessary.
The TLS consists in two orthogonal diagnostic X-ray sources fixed to the ceiling and aimed towards two flat panel detectors integrated into the floor. This system requires the acquisition of several pairs of images in order to localize the target position. These images are performed with frequency and exposition data decided by the radiographer, during the entire treatment.
Aim of this study is the evaluation of TLS Air Kerma of CyberKnife system, installed at the European Institute of Oncology (Milan – Italy) and an evaluation of the imaging-dependant dose in a clinical patient population receiving CyberKnife radiotherapy treatment.
All the measurements were performed with an ionization chamber positioned at the center point of imaging of the CyberKnife® treatment room, in the point of intersection of the two main axes of X-ray beams. The chamber was connected to an electrometer and all the readings were corrected for environmental conditions (atmospheric pressure and room temperature) and calibration constant. A series of Air Kerma values were obtained by varying the exposure parameters of CyberKnife® imaging system (electric potential difference and electric charge). These permitted to create a polynomial equation that allows a realistic evaluation of the dose due to the imaging. The measured and calculated values for the same points were compared in order to estimate the accuracy of our equation. An overview of the exposure parameters in a sample of clinical population treated in our centre, were then performed. With these parameters we calculated the Air Kerma values. These values were then compared with the values provided by the software of the CyberKnife®.
The Air Kerma values we calculated showed a percentage variation value of ±1.8%, with a maximum of ±4.4% when compared with measured Air Kerma values. The analysis of the Air Kerma values of the clinical sample showed that the CyberKnife® software underestimate the dose of the imaging when compared with the dose we calculated.
The Air Kerma depends on electric potential difference and electric charge values choose by the radiographer and on the overall number of radiographic pairs, needed for a complete SRS or SBRT treatment.
In general the target localization with the 6D Skull system, needs a lower number of images and lower electric potential difference and electric charge values than X-Sight Spine, so the imaging-dependent dose is lower for patients when the 6D Skull tracking system is used.
In our clinical sample the estimated average dose added by the imaging is 0.1% (for 6D Skull) and 0.3% (for X-Sight Spine) of the therapeutic dose
Malignant Mesothelioma of Spermatic Cord in an Elderly Man with a History of Asbestos Exposure
No full textWe report a case of malignant mesothelioma of the spermatic cord in 80-year-old man presented with retained testis, hydrocele, and right inguinal mass. The patient had a long history of asbestos exposure as a railway worker. The patient was submitted to inguinal radical orchiectomy. One year after surgery, the patient is alive without signs of disease. Malignant mesothelioma of spermatic cord is a very rare disease, but this diagnosis should be suspected in patient with a history of asbestos exposure
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