An error estimate of Gaussian Recursive Filter in 3Dvar problem

Computational kernel of the three-dimensional variational data assimilation (3D-Var) problem is a linear system, generally solved by means of an iterative method. The most costly part of each iterative step is a matrix-vector product with a very large covariance matrix having Gaussian correlation structure. This operation may be interpreted as a Gaussian convolution, that is a very expensive numerical kernel. Recursive Filters (RFs) are a well known way to approximate the Gaussian convolution and are intensively applied in the meteorology, in the oceanography and in forecast models. In this paper, we deal with an oceanographic 3D-Var data assimilation scheme, named OceanVar, where the linear system is solved by using the Conjugate Gradient (GC) method by replacing, at each step, the Gaussian convolution with RFs. Here we give theoretical issues on the discrete convolution approximation with a first order (1st-RF) and a third order (3rd-RF) recursive filters. Numerical experiments confirm given error bounds and show the benefits, in terms of accuracy and performance, of the 3-rd RF.Comment: 9 page

Resting-state connectivity and functional specialization in human medial parieto-occipital cortex

According to recent models of visuo-spatial processing, the medial parieto-occipital cortex is a crucial node of the dorsal visual stream. Evidence from neurophysiological studies in monkeys has indicated that the parieto-occipital sulcus (POS) contains three functionally and cytoarchitectonically distinct areas: the visual area V6 in the fundus of the POS, and the visuo-motor areas V6Av and V6Ad in a progressively dorsal and anterior location with respect to V6. Besides different topographical organization, cytoarchitectonics, and functional properties, these three monkey areas can also be distinguished based on their patterns of cortico-cortical connections. Thanks to wide-field retinotopic mapping, areas V6 and V6Av have been also mapped in the human brain. Here, using a combined approach of resting-state functional connectivity and task-evoked activity by fMRI, we identified a new region in the anterior POS showing a pattern of functional properties and cortical connections that suggests a homology with the monkey area V6Ad. In addition, we observed distinct patterns of cortical connections associated with the human V6 and V6Av which are remarkably consistent with those showed by the anatomical tracing studies in the corresponding monkey areas. Consistent with recent models on visuo-spatial processing, our findings demonstrate a gradient of functional specialization and cortical connections within the human POS, with more posterior regions primarily dedicated to the analysis of visual attributes useful for spatial navigation and more anterior regions primarily dedicated to analyses of spatial information relevant for goal-directed action

Absence of signatures of Weyl orbits in the thickness dependence of quantum transport in cadmium arsenide

In a Weyl orbit, the Fermi arc surface states on opposite surfaces of the topological semimetal are connected through the bulk Weyl or Dirac nodes. Having a real-space component, these orbits accumulate a sample-size-dependent phase. Following recent work on the three-dimensional Dirac semimetal cadmium arsenide (Cd3As2), we have sought evidence for this thickness-dependent effect in quantum oscillations and quantum Hall plateaus in (112)-oriented Cd3As2 thin films grown by molecular beam epitaxy. We compare quantum transport in films of varying thickness at apparently identical gate-tuned carrier concentrations and find no clear dependence of the relative phase of the quantum oscillations on the sample thickness. We show that small variations in carrier densities, difficult to detect in low-field Hall measurements, lead to shifts in quantum oscillations that are commensurate with previously reported phase shifts. Future claims of Weyl orbits based on the thickness dependence of quantum transport data require additional studies that demonstrate that these competing effects have been disentangled

Basal-plane growth of cadmium arsenide by molecular beam epitaxy

(001)-oriented thin films of the three-dimensional Dirac semimetal cadmium arsenide can realize a quantum spin Hall insulator and other kinds of topological physics, all within the flexible architecture of epitaxial heterostructures. Here, we report a method for growing (001) cadmium arsenide films using molecular beam epitaxy. The introduction of a thin indium arsenide wetting layer improves surface morphology and structural characteristics, as measured by x-ray diffraction and reflectivity, atomic force microscopy, and scanning transmission electron microscopy. The electron mobility of 50-nm-thick films is found to be 9300 cm2/Vs at 2 K, comparable to the highest-quality films grown in the conventional (112) orientation. This work demonstrates a simple experimental framework for exploring topological phases that are predicted to exist in proximity to the three-dimensional Dirac semimetal phase

Observation of the quantum Hall effect in confined films of the three-dimensional Dirac semimetal Cd3As2

The magnetotransport properties of epitaxial films of Cd3As2, a paradigm three-dimensional Dirac semimetal, are investigated. We show that an energy gap opens in the bulk electronic states of sufficiently thin films and, at low temperatures, carriers residing in surface states dominate the electrical transport. The carriers in these states are sufficiently mobile to give rise to a quantized Hall effect. The sharp quantization demonstrates surface transport that is virtually free of parasitic bulk conduction and paves the way for novel quantum transport studies in this class of topological materials. Our results also demonstrate that heterostructuring approaches can be used to study and engineer quantum states in topological semimetals.Comment: Accepted, Phys. Rev. Let

A non-linear observer for unsteady three-dimensional flows

A method is proposed to estimate the velocity field of an unsteady flow using a limited number of flow measurements. The method is based on a non-linear low-dimensional model of the flow and on expanding the velocity field in terms of empirical basis functions. The main idea is to impose that the coefficients of the modal expansion of the velocity field give the best approximation to the available measurements and that at the same time they satisfy as close as possible the non-linear low-order model. The practical use may range from feedback flow control to monitoring of the flow in non-accessible regions. The proposed technique is applied to the flow around a confined square cylinder, both in two- and three-dimensional laminar flow regimes. Comparisons are provided. with existing linear and non-linear estimation techniques

Application of the Cloude-Pottier decomposition to weather radar signatures

In this paper we apply the Cloude-Pottier decomposition to Weather Radar Signatures. First, we present the results of a simulation carried out at the Chemnitz University of Technology and give the expected H-α values for different rain intensities. A comparison with standard radarmeteorological variables is also given. Then, first ever images of Entropy and Anisotropy are presented for clouds and precipitation. Experimental Data are from the POLDIRAD Weather Facility in Oberpfaffenhofen, Germany

Dupilumab in chronic rhinosinusitis with nasal polyps: Real life data in a multicentric Sicilian experience

Objective: This study aimed to evaluate the effectiveness and safety of dupilumab during the first year of treatment in a real-life setting, focusing on improvement in nasal polyp score (NPS) as well as specific symptoms, quality of life and olfactory function. Methodology/principal: A multicentric observational cohort study was carried out. A total of 170 patients were enrolled in the Otorhinolaryngology Unit of the three University Hospitals and considered for dupilumab therapy. All recorder characteristics were age (at the first dupilumab application visit), sex, smoke habits, previous local and systemic corticosteroid therapy, history of endoscopic sinus surgery, number of previous endoscopic sinus surgery, concomitant asthma, history of an allergic condition, immunoglobulin E (IgE), allergy to nonsteroidal anti-inflammatory drugs (NSAIDs), Aspirin Exacerbated Respiratory Disease (AERD), other comorbidities associated, blood eosinophils, nasal polyp score, sinonasal outcome test 22 (SNOT 22), sniffin' stick test, the start date of dupilumab therapy and number of doses of dupilumab and eventually, Dupilumab's adverse events related to administration. The Wilcoxon test for dependent samples was performed to compare variables. Statistical significance was assumed for p values < 0.05. Results: A statistically significant reduction in SNOT-22 and NPS was shown at the 6th and 12th month compared to baseline values (p < 0.001 for both comparisons). A statistically significant increase value at the Sniffin' sticks test was shown in the 6th and 12th month compared to baseline values (p < 0.001 for both comparisons). At the 12-month follow-up, according to EUFOREA indications, all patients were considered to remain in treatment with dupilumab and continued the treatment because of a reduced NPS, improved quality of life and a reduced need for system corticosteroids. Dupilumab seemed to be well tolerated by all patients. Any adverse effect of the drug led to the quit of biological treatment. Conclusions: This multi-centric real-life study supported the effectiveness of dupilumab as an add-on therapy to intranasal corticosteroids in patients with severe uncontrolled CRSwNP in improvement of quality of life, severity of symptoms, polyp size reduction and smell function. Furthermore, our data support the safety profile of monoclonal therapy with dupilumab