Bregman Cost for Non-Gaussian Noise

One of the tasks of the Bayesian inverse problem is to find a good estimate based on the posterior probability density. The most common point estimators are the conditional mean (CM) and maximum a posteriori (MAP) estimates, which correspond to the mean and the mode of the posterior, respectively. From a theoretical point of view it has been argued that the MAP estimate is only in an asymptotic sense a Bayes estimator for the uniform cost function, while the CM estimate is a Bayes estimator for the means squared cost function. Recently, it has been proven that the MAP estimate is a proper Bayes estimator for the Bregman cost if the image is corrupted by Gaussian noise. In this work we extend this result to other noise models with log-concave likelihood density, by introducing two related Bregman cost functions for which the CM and the MAP estimates are proper Bayes estimators. Moreover, we also prove that the CM estimate outperforms the MAP estimate, when the error is measured in a certain Bregman distance, a result previously unknown also in the case of additive Gaussian noise

Identification of Multiple Hard X-Ray Sources in Solar Flares: A Bayesian Analysis of the 2002 February 20 Event

The hard X-ray emission in a solar flare is typically characterized by a number of discrete sources, each with its own spectral, temporal, and spatial variability. Establishing the relationship among these sources is critical to determining the role of each in the energy release and transport processes that occur within the flare. In this paper we present a novel method to identify and characterize each source of hard X-ray emission. The\uf0a0method permits a quantitative determination of the most likely number of subsources present, and of the relative probabilities that the hard X-ray emission in a given subregion of the flare is represented by a complicated multiple source structure or by a simpler single source. We apply the method to a well-studied flare on 2002 February 20 in order to assess competing claims as to the number of chromospheric footpoint sources present, and hence to the complexity of the underlying magnetic geometry/topology. Contrary to previous claims of the need for multiple sources to account for the chromospheric hard X-ray emission at different locations and times, we find that a simple two-footpoint-plus-coronal-source model is the most probable explanation for the data. We also find that one of the footpoint sources moves quite rapidly throughout the event, a factor that presumably complicated previous analyses. The inferred velocity of the footpoint corresponds to a very high induced electric field, compatible with the fields in thin reconnecting current sheets

Body mass index and baseline platelet count as predictive factors in Merkel cell carcinoma patients treated with avelumab

BackgroundMerkel cell carcinoma (MCC) is a rare and aggressive skin cancer, associated with a worse prognosis. The Immune Checkpoint Inhibitors (ICIs) avelumab and pembrolizumab have been recently approved as first-line treatment in metastatic MCC (mMCC). The clinical observation of improved outcomes in obese patients following treatment with ICIs, known as the “obesity paradox”, has been studied across many types of tumors. Probably due to the rarity of this tumor, data on mMMC patients are lacking.Patients and methodsThis is an observational, hospital-based, study to investigate the role of Body Mass Index (BMI) as predictive biomarker of ICI response in mMCC patients treated with avelumab as first-line treatment. The study population included the patients treated from February 2019 to October 2022 in an Italian referral center for rare tumors. Clinico-pathological characteristics, BMI, laboratory parameters (NLR and platelet count), and response to avelumab were analyzed from a MCC System database prospectively collected.ResultsThirty-two (32) patients were included. Notably, the presence of pre-treatment BMI ≥ 30 was significantly associated with longer PFS [BMI < 30 Group: median PFS, 4 months (95% CI: 2.5-5.4); BMI ≥ 30 Group: median PFS, not reached; p<0.001)[. Additionally, the median PFS was significantly higher in patients with higher PLT (median PFS: 10 months in the “low PLT” Group (95% CI: 4.9, 16.1) vs 33 months (95% CI: 24.3, 43.2) in the “high PLT” Group (p=0.006). The multivariable Cox regression model confirmed these results.ConclusionTo our knowledge, this is the first study that investigates the predictive role of BMI in MCC patients. Our data were consistent with the clinical observation of improved outcomes in obese patients across other tumor types. Thus, advanced age, a weakened immune system, and the obesity-associated “inflammaging”, are key factors that could impact the cancer immune responses of mMCC patients

Recupero termico da motori a gas naturale con ciclo Brayton invertito: analisi di un caso stradale e marittimo

In seguito a normative sempre più stringenti sulle emissioni nel settore dei trasporti, è cresciuto l'interesse nella riduzione dei consumi e nella ricerca di combustibili più puliti, come il gas naturale liquefatto (GNL). In quest'ottica, il recupero dell'energia residua dai gas di scarico da motori alternativi a combustione interna (MCI), rappresenta una delle tematiche più studiate. In questa trattazione, è stato analizzato un sistema di recupero termico da motori a combustione interna alimentati a gas naturale basato sul Ciclo Brayton Invertito (IBC), con l'obiettivo di valutarne la fattibilità tecnico-economica per due potenziali applicazioni: un mezzo pesante adibito al trasporto stradale di merci ed un traghetto. Per la scelta del punto di progetto per il sistema di recupero, nel caso di veicolo pesante destinato al trasporto merci a lungo raggio è fatto riferimento a tratte di tipo autostradale, percorse a velocità di crociera. Per quanto riguarda il traghetto, è stata considerata una velocità di crociera media relativa a traghetti bidirezionali per tratte medio-brevi. Per entrambi i casi di studio è stata condotta un'analisi termodinamica mediante il software Aspen HYSYS, ed è stata valutata la possibilità di utilizzo del processo di rigassificazione del GNL per migliorare il recupero energetico. Per quanto riguarda il risparmio di combustibile ottenibile nel caso di studio stradale è stato tenuto conto dell'aumento dei consumi relativo al peso del sistema IBC installato a bordo, aspetto trascurabile invece nel caso navale. I risultati mostrano una potenza massima recuperabile in termini percentuali rispetto alla potenza erogata dal motore di circa il 2% per il caso stradale e del 4,4% per il traghetto. Per quanto riguarda i risultati economici, questi hanno mostrato per il caso stradale un risparmio sul combustibile non sufficiente a giustificare l'investimento iniziale. Diversi sono invece i risultati ottenuti dall'analisi del caso navale che, per un profilo di utilizzo del sistema di recupero di circa 6000 ore equivalenti, hanno mostrato il rientro dell'investimento in circa 13 anni

Total Variation Based Parameter-Free Model for Impulse Noise Removal

AbstractWe propose a new two-phase method for reconstruction of blurred images corrupted by impulse noise. In the first phase, we use a noise detector to identify the pixels that are contaminated by noise, and then, in the second phase, we reconstruct the noisy pixels by solving an equality constrained total variation minimization problem that preserves the exact values of the noise-free pixels. For images that are only corrupted by impulse noise (i.e., not blurred) we apply the semismooth Newton's method to a reduced problem, and if the images are also blurred, we solve the equality constrained reconstruction problem using a first-order primal-dual algorithm. The proposed model improves the computational efficiency (in the denoising case) and has the advantage of being regularization parameter-free. Our numerical results suggest that the method is competitive in terms of its restoration capabilities with respect to the other two-phase methods.</jats:p

Whiteness Constraints in a Unified Variational Framework for Image Restoration

We propose a robust variational model for the restoration of images corrupted by blur and the general class of additive white noises. The key idea behind our proposal relies on a novel hard constraint imposed on the residual of the restoration, namely we characterize a residual whiteness set to which the restored image must belong. As the feasible set is unbounded, solution existence results for the proposed variational model are given. Moreover, based on theoretical derivations as well as on Monte Carlo simulations, we provide well-founded guidelines for setting the whiteness constraint limits. The solution of the non-trivial optimization problem, due to the non-smooth non-convex proposed model, is efficiently obtained by an alternating directions method of multipliers, which in particular reduces the solution to a sequence of convex optimization subproblems. Numerical results show the potentiality of the proposed model for restoring blurred images corrupted by several kinds of additive white noises

A Unified Framework for the Restoration of Images Corrupted by Additive White Noise

We propose a robust variational model for the restoration of images corrupted by blur and the general class of additive white noises. The solution of the non-trivial optimization problem, due to the non-smooth non-convex proposed model, is efficiently obtained by an Alternating Directions Method of Multipliers (ADMM), which in particular reduces the solution to a sequence of convex optimization sub-problems. Numerical results show the potentiality of the proposed model for restoring blurred images corrupted by several kinds of additive white noises