Summary
Score-driven models have recently been introduced as a general framework to specify time-varying parameters of conditional densities. The score enjoys stochastic properties that make these ...models easy to implement and convenient to apply in several contexts, ranging from biostatistics to finance. Score-driven parameter updates have been shown to be optimal in terms of locally reducing a local version of the Kullback–Leibler divergence between the true conditional density and the postulated density of the model. A key limitation of such an optimality property is that it holds only locally both in the parameter space and sample space, yielding to a definition of local Kullback–Leibler divergence that is in fact not a divergence measure. The current paper shows that score-driven updates satisfy stronger optimality properties that are based on a global definition of Kullback–Leibler divergence. In particular, it is shown that score-driven updates reduce the distance between the expected updated parameter and the pseudo-true parameter. Furthermore, depending on the conditional density and the scaling of the score, the optimality result can hold globally over the parameter space, which can be viewed as a generalization of the monotonicity property of the stochastic gradient descent scheme. Several examples illustrate how the results derived in the paper apply to specific models under different easy-to-check assumptions, and provide a formal method to select the link function and the scaling of the score.
Improving the detection efficiency in nuclear emulsion trackers Alexandrov, A.; Bozza, C.; Buonaura, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2015, Letnik:
776
Journal Article
Recenzirano
Nuclear emulsion films are a tracking device with unique space resolution. Their use in nowadays large-scale experiments relies on the availability of automated microscope operating at very high ...speed. In this paper we describe the features and the latest improvements of the European Scanning System, a last-generation automated microscope for emulsion scanning. In particular, we present a new method for the recovery of tracking inefficiencies. Stacks of double coated emulsion films have been exposed to a 10GeV/c pion beam. Efficiencies as high as 98% have been achieved for minimum ionising particle tracks perpendicular to the emulsion films and of 93% for tracks with tan(θ)≃0.8.
We consider the problem of tracking an unknown time varying parameter that characterizes the probabilistic evolution of a sequence of independent observations. To this aim, we propose a stochastic ...gradient descent-based recursive scheme in which the log-likelihood of the observations acts as time varying gain function. We prove convergence in mean-square error in a suitable neighbourhood of the unknown time varying parameter and illustrate the details of our findings in the case where data are generated from distributions belonging to the exponential family.
During the past 20 years, historians have made great strides in studying the engagement of rural communities with the formation of nations and states in nineteenth-century Latin America. The ...formation of citizenship, popular liberalism, local pueblo sovereignty, and alternative nationalisms and the influence of local struggles on state institutions have all been plotted, from very local communities to regions. However, the recent emphasis on the integration of peasant communities into regional and national history has largely failed to highlight the importance of provincial cities, even as it gives ample evidence of how important they became as bridges between the local, the regional, and the national.
Glucocorticoids (GCs) are considered drugs of choice for treating nasal polyps (NPs). However, a subset of patients shows a limited clinical response even to high doses of GCs. Altered expression of ...glucocorticoid receptors (GRs), namely GR-alpha; and GR-beta;, is a potential mechanism underlying GC insensitivity. GCs modulate the expression of several cytokines, including transforming growth factor-beta (TGF-beta), which may contribute to cellular proliferation in NPs. The study investigates some biomolecular features of GC-resistant NPs, and examines possible differences from normal mucosa (NM).
Radioligand binding assay (binding) was used to determine GR-alpha; binding capacity; Western blotting was used to evaluate GR-alpha;, GR-beta;, and TGF-beta; expression and GR-alpha; subcellular distribution. NPs were sampled in 32 patients during ethmoidectomy; NM was taken from 15 healthy patients during rhinoplasty.
GR-alpha; was present in NPs and NM, with lower affinity for the ligand in NPs. GR-alpha; was prevalent in the cytosol of NPs that were GR-alpha-negative to the binding assay. GR-beta was expressed in NPs and absent in the majority of NM. TGF-beta1 expression was higher in NPs than in NM.
GR-beta and TGF-beta1 might be involved in NP pathogenesis, but their role in modulating GC sensitivity is still unclear.
We investigate the effects of erbium doping on SnO2 nanoclustering in Sn-doped silica. Vibrational spectroscopy data from Raman and infrared absorption measurements show nanostructuring effects on ...the SnO2 nanophase. Ultraviolet absorption spectra evidence a gap shift ascribable to size-dependent quantum confinement, also suggesting a role of erbium doping in determining cluster sizes and the amount of localized states on the nanophase boundary. Transmission electron microscopy confirms and details the spectroscopic data. As a result of these measurements, we find that the nanocrystal size distribution becomes narrower, increasing the erbium concentration, while the density of localized states at the nanocrystal surface decreases. The distribution of erbium ions among the possible environments is then examined through simultaneous spectroscopy of luminescence excited by nanocrystal-to-erbium energy transfer and the absorption of nanocrystal luminescence by erbium ions. This analysis shows that erbium behaves as an extrinsic nucleation centre of the SnO2 nanophase at low doping levels, whereas at high concentrations it modifies the matrix, hindering the growth of SnO2 crystals and passivating the interface.
The main purpose of the present paper is to cover the lack of a reference point in the literature providing a comprehensive review of the state of the art, recent developments, and future challenges ...relatives to analytical, experimental, and numerical approaches tailored for the field of dynamic characterization of floating offshore wind turbines, with a focus on aerodynamics, hydrodynamics, and anchoring systems. The Real Time Hybrid Approach makes it possible to overcome some of the problems associated with the scaling laws of the classical experimental approach, so the development of advanced actuators in association with numerical models that can guarantee accurate simulation and low computational burden are the main challenges of these approaches. In the field of numerical modeling, Smoothed Particle Hydrodynamics methods show the highest levels of accuracy for studying fluid–structure interaction. Associated with this, the identification of analytical or semi-analytical formulations to solve coupled problems related to the dynamic characterization of floating offshore wind turbines could offer considerable contribution to overcome the limitations arising from the computational burdens of numerical methods. For future developments, additional topics of interest include a deeper investigation in terms of control strategies, wind farms, including wake effects, shared anchors, and mooring lines, as well as the use of new materials in mooring lines.
•Increase investigation of comprehensive analytic solutions.•Requirement for developing efficient, high-fidelity fully coupled numerical models.•Necessity of improving the actuator system for the Real Time Hybrid Approach.
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