7,111 research outputs found

    Probabilistic Inference from Arbitrary Uncertainty using Mixtures of Factorized Generalized Gaussians

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    This paper presents a general and efficient framework for probabilistic inference and learning from arbitrary uncertain information. It exploits the calculation properties of finite mixture models, conjugate families and factorization. Both the joint probability density of the variables and the likelihood function of the (objective or subjective) observation are approximated by a special mixture model, in such a way that any desired conditional distribution can be directly obtained without numerical integration. We have developed an extended version of the expectation maximization (EM) algorithm to estimate the parameters of mixture models from uncertain training examples (indirect observations). As a consequence, any piece of exact or uncertain information about both input and output values is consistently handled in the inference and learning stages. This ability, extremely useful in certain situations, is not found in most alternative methods. The proposed framework is formally justified from standard probabilistic principles and illustrative examples are provided in the fields of nonparametric pattern classification, nonlinear regression and pattern completion. Finally, experiments on a real application and comparative results over standard databases provide empirical evidence of the utility of the method in a wide range of applications

    A Study of Two-Temperature Non-Equilibrium Ising Models: Critical Behavior and Universality

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    We study a class of 2D non-equilibrium Ising models based on competing dynamics induced by contact with heat-baths at two different temperatures. We make a comparative study of the non-equilibrium versions of Metropolis, heat bath/Glauber and Swendsen-Wang dynamics and focus on their critical behavior in order to understand their universality classes. We present strong evidence that some of these dynamics have the same critical exponents and belong to the same universality class as the equilibrium 2D Ising model. We show that the bond version of the Swendsen-Wang update algorithm can be mapped into an equilibrium model at an effective temperature.Comment: 12 pages of LaTeX plus 18 pages of postscript figures in a uuencoded file (608k

    Stability and Reversible Oxidation of Sub-Nanometric Cu5 Metal Clusters: Integrated Experimental Study and Theoretical Modeling**

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    Sub-nanometer metal clusters have special physical and chemical properties, significantly different from those of nanoparticles. However, there is a major concern about their thermal stability and susceptibility to oxidation. In situ X-ray Absorption spectroscopy and Near Ambient Pressure X-ray Photoelectron spectroscopy results reveal that supported Cu5 clusters are resistant to irreversible oxidation at least up to 773 K, even in the presence of 0.15 mbar of oxygen. These experimental findings can be formally described by a theoretical model which combines dispersion-corrected DFT and first principles thermochemistry revealing that most of the adsorbed O2 molecules are transformed into superoxo and peroxo species by an interplay of collective charge transfer within the network of Cu atoms and large amplitude “breathing” motions. A chemical phase diagram for Cu oxidation states of the Cu5-oxygen system is presented, clearly different from the already known bulk and nano-structured chemistry of Cu

    Silicon quantum dots in photovoltaic devices: device fabrication, characterization and comparison of materials

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    The realization of crystalline silicon tandem solar cells relies on silicon nanocrystal (Si NC) quantum dots as the absorber of the top solar cell. Quantum confinement of charge carriers within the nanocrystals permits to achieve a band gap up to 2 eV which can be adjusted according to the size of the nanocrystals. This enables the construction of all-crystalline Si tandem solar cells, and increases the theoretical efficiency limit from 33 % to 42.5 % due to the addition of a second band gap. In this work, the electrical and photovoltaic properties of Si NC films are assessed and the most prominent material systems (SiO2, Si3N4, SiC) are compared. P-i-n solar cells are presented which feature Si NC as the intrinsic absorber layer and permit to characterize quantum confinement electrically on device level. P-i-n solar cells with Si NC in SiC in the i-region have yielded open circuit voltages of up to 370mV

    Multi-Wavelength Observations of the Blazar 1ES 1011+496 in Spring 2008

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    The BL Lac object 1ES 1011+496 was discovered at Very High Energy gamma-rays by MAGIC in spring 2007. Before that the source was little studied in different wavelengths. Therefore a multi-wavelength (MWL) campaign was organized in spring 2008. Along MAGIC, the MWL campaign included the Metsahovi radio observatory, Bell and KVA optical telescopes and the Swift and AGILE satellites. MAGIC observations span from March to May, 2008 for a total of 27.9 hours, of which 19.4 hours remained after quality cuts. The light curve showed no significant variability. The differential VHE spectrum could be described with a power-law function. Both results were similar to those obtained during the discovery. Swift XRT observations revealed an X-ray flare, characterized by a harder when brighter trend, as is typical for high synchrotron peak BL Lac objects (HBL). Strong optical variability was found during the campaign, but no conclusion on the connection between the optical and VHE gamma-ray bands could be drawn. The contemporaneous SED shows a synchrotron dominated source, unlike concluded in previous work based on nonsimultaneous data, and is well described by a standard one zone synchrotron self Compton model. We also performed a study on the source classification. While the optical and X-ray data taken during our campaign show typical characteristics of an HBL, we suggest, based on archival data, that 1ES 1011+496 is actually a borderline case between intermediate and high synchrotron peak frequency BL Lac objects.Comment: 13 pages, accepted for publication in MNRA

    The major upgrade of the MAGIC telescopes, Part II: A performance study using observations of the Crab Nebula

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    MAGIC is a system of two Imaging Atmospheric Cherenkov Telescopes located in the Canary island of La Palma, Spain. During summer 2011 and 2012 it underwent a series of upgrades, involving the exchange of the MAGIC-I camera and its trigger system, as well as the upgrade of the readout system of both telescopes. We use observations of the Crab Nebula taken at low and medium zenith angles to assess the key performance parameters of the MAGIC stereo system. For low zenith angle observations, the standard trigger threshold of the MAGIC telescopes is ~50GeV. The integral sensitivity for point-like sources with Crab Nebula-like spectrum above 220GeV is (0.66+/-0.03)% of Crab Nebula flux in 50 h of observations. The angular resolution, defined as the sigma of a 2-dimensional Gaussian distribution, at those energies is < 0.07 degree, while the energy resolution is 16%. We also re-evaluate the effect of the systematic uncertainty on the data taken with the MAGIC telescopes after the upgrade. We estimate that the systematic uncertainties can be divided in the following components: < 15% in energy scale, 11-18% in flux normalization and +/-0.15 for the energy spectrum power-law slope.Comment: 21 pages, 25 figures, accepted for publication in Astroparticle Physic

    EP05.02-003 Durvalumab after Chemoradiotherapy (CRT) in Unresectable Stage III NSCLC. Comparative Study of Two Cohorts in the Real-World Setting

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    [EN] Introduction: Durvalumab is the new standard of care for unresectable locally advanced NSCLC, with PD-L1 _1% and who did not have progression after CRT treatment in the European Union. Our study compares the effectiveness and the frequency of radiation pneumonitis in patients treated with concurrent CRT with or without durvalumab consolidation during the same period in real clinical practice. Methods: A single-center retrospective study. 71 treated patients with unresectable stage III NSCLC were included between March 2018 and December 2021, 37 with CRT followed by durvalumab and 34 with CRT alone. Real-world progression-free survival (rwPFS) and real-world overall survival (rwOS) were calculated since the date of the end CRT. Propensity score matching (PSM) 1:1 was used to account for differences in baseline characteristics. Results: Median age was 67 years (range 46-82). 25.4% of the patients were _75 years old. 78.9% were men and 53.5% former smokers. 54.9% had squamous histology and 28%, 51% and 21% stage IIIA, IIIB and IIIC disease, respectively. The most used scheme was carboplatinpaclitaxel (43.7%), receiving induction chemotherapy in up to 54.9% of patients. 73.2% received between 60-66 Gy doses of radiotherapy. Median time from end of CRT to onset durvalumab was 44 days (range 13-120) with a median of 14 infusions (range 6-27). Of the 34 patients without durvalumab treatment, the expression PD-L1 <1% (58.8%) was the most frequent cause for rejecting consolidation therapy. After PSM analysis, patients distributions were well balanced. With a median follow-up of 19.7 months (range 1.4-36.6); median rw-PFS was 9.3 months (95% CI, 5-13.5) without durvalumab and 17 months (95% CI, 11-22.9) with durvalumab (pÂĽ0.013). Median rw-OS was 19.3 months (95% CI, 3.8-34.8) without durvalumab and 29.9 months (95% CI, 23.3-36.6) with durvalumab (pÂĽ0.241) with a rw-OS% at 6, 18 and 24 months of 90%, 62% and 49% vs 100%, 86% and 74%, respectively. The rate of radiation pneumonitis was more frequent with durvalumab consolidation (56.8% against 44.1%), (pÂĽ0.346), especially within 3 months after CRT. G3 pneumonitis was only observed in the consolidation therapy. Conclusions: Our results demonstrate the effectiveness of durvalumab consolidation after CRT in real-world patients with unresectable stage III NSCLC. Further sample and longer follow-up are required to obtain more accurate results. Active surveillance and appropriate management for radiation pneumonitis are needed, in especially in candidates for consolidation treatmentS
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