Nanofriction behavior of cluster-assembled carbon films

We have characterized the frictional properties of nanostructured (ns) carbon films grown by Supersonic Cluster Beam Deposition (SCBD) via an Atomic Force-Friction Force Microscope (AFM-FFM). The experimental data are discussed on the basis of a modified Amonton's law for friction, stating a linear dependence of friction on load plus an adhesive offset accounting for a finite friction force in the limit of null total applied load. Molecular Dynamics simulations of the interaction of the AFM tip with the nanostructured carbon confirm the validity of the friction model used for this system. Experimental results show that the friction coefficient is not influenced by the nanostructure of the films nor by the relative humidity. On the other hand the adhesion coefficient depends on these parameters.Comment: 22 pages, 6 figures, RevTex

Schur functions and their realizations in the slice hyperholomorphic setting

we start the study of Schur analysis in the quaternionic setting using the theory of slice hyperholomorphic functions. The novelty of our approach is that slice hyperholomorphic functions allows to write realizations in terms of a suitable resolvent, the so called S-resolvent operator and to extend several results that hold in the complex case to the quaternionic case. We discuss reproducing kernels, positive definite functions in this setting and we show how they can be obtained in our setting using the extension operator and the slice regular product. We define Schur multipliers, and find their co-isometric realization in terms of the associated de Branges-Rovnyak space

A novel CMB polarization likelihood package for large angular scales built from combined WMAP and Planck LFI legacy maps

We present a CMB large-scale polarization dataset obtained by combining WMAP Ka, Q and V with Planck 70 GHz maps. We employ the legacy frequency maps released by the WMAP and Planck collaborations and perform our own Galactic foreground mitigation technique, which relies on Planck 353 GHz for polarized dust and on Planck 30 GHz and WMAP K for polarized synchrotron. We derive a single, optimally-noise-weighted, low-residual-foreground map and the accompanying noise covariance matrix. These are shown, through $\chi^2$ analysis, to be robust over an ample collection of Galactic masks. We use this dataset, along with the Planck legacy Commander temperature solution, to build a pixel-based low-resolution CMB likelihood package, whose robustness we test extensively with the aid of simulations, finding excellent consistency. Using this likelihood package alone, we constrain the optical depth to reionazation $\tau=0.069^{+0.011}_{-0.012}$ at $68\%$ C.L., on 54\% of the sky. Adding the Planck high-$\ell$ temperature and polarization legacy likelihood, the Planck lensing likelihood and BAO observations we find $\tau=0.0714_{-0.0096}^{+0.0087}$ in a full $\Lambda$CDM exploration. The latter bounds are slightly less constraining than those obtained employing \Planck\ HFI CMB data for large angle polarization, that only include EE correlations. Our bounds are based on a largely independent dataset that does include also TE correlations. They are generally well compatible with Planck HFI preferring slightly higher values of $\tau$. We make the low-resolution Planck and WMAP joint dataset publicly available along with the accompanying likelihood code.Comment: The WMAP+LFI likelihood module is available on \http://www.fe.infn.it/u/pagano/low_ell_datasets/wmap_lfi_legacy

Sensitivity analysis of cohesive zone model parameters to simulate hydrogen embrittlement effect

For many steels and alloys used in engineering field, the presence of atomic hydrogen in working environment can produce a deleterious effect. In fact, when this small element penetrates into the material lattice induces a drastically decrease of the mechanical properties. This process is known as hydrogen embrittlement. This complex phenomenon involves chemical and physical factors that are strictly dependent on the microstructure of the material. Some examples are hydrogen diffusivity, solubility of hydrogen into the material and concentration related not only to the interstitial lattice sites (NILS) but also to the traps sites that is the most difficult part to quantify. The present work starts from the development of 2D finite elements cohesive zone model reproducing a toughness test of a high-strength low carbon steel, AISI 4130 operating in hydrogen-contaminated environment. With three consequent steps of simulations, the model implements diffusion and crack propagation analyses using cohesive elements. The embrittlement effect of hydrogen is considered by decreasing the cohesive law (TSL), which expresses the constitutive response of the material to the fracture behavior, based on the total hydrogen concentration. It includes NILS and traps sites. Aim of the work is a sensitivity analysis of the parameters included into the model. In particular, the influence of the hydrogen diffusion coefficient as well as the initial concentration set to calculate the total hydrogen concentration at the crack tip are taken into account. Both a comparison of the values used in the model with literature data and a critical discussion of the results obtained by the sensitivity analysis will be presented

Visual Models for Social Media Image Analysis: Groupings, Engagement, Trends, and Rankings

With social media image analysis, one collects and interprets online images for the study of topical affairs. This analytical undertaking requires formats for displaying collections of images that enable their inspection. First, we discuss features of social media images to make a case for studying them in groups (rather than individually): multiplicity, circulation, modification, networkedness, and platform specificity. In all, these offer reasons and means for an approach to social media image research that privileges the collection of images as its analytical object. Second, taking the 2019 Amazon rainforest fires as a case study, we present four visual models for analyzing collections of social media images. Each visual model matches a distinctive spatial arrangement with a type of analysis: grouping images by theme with clusters, surfacing dominant images and their engagement with treemaps, following image trends with plots, and comparing image rankings across platforms with grids

Lo studio FAST: FAringotonsillite STreptococcica in età pediatrica Impatto farmacoeconomico delle Linee Guida dell'American Academy of Pediatrics sulla pratica clinica di 600 pediatri italiani

The American Academy of Pediatrics (AAP) has recently published its new guidelines for the treatment of pediatric tonsillopharyngitis; a diagnostic test for the detection of streptococci is recommended, followed by a treatment with penicillins (10 days) or cephalosporins (5 days) in case of positivity, and by no treatment otherwise. The success of a guideline, in general, depends on its diffusion in practice and on its adaptability to different local settings. The aim of the present study (FAST) was the evaluation of the clinical and economical impact of the application of the AAP guidelines in the Italian reality. The study was conducted with the cooperation of 600 pediatricians, uniformly distributed on the Italian territory, and involved 3072 patients. The pediatricians were left free to decide whether to follow the guidelines or not. The results of the analysis indicate that only some 20% of the pediatricians adhered to the suggested protocol; the total cost (calculated in the perspective of the National Health System, with a time horizon of about 3 months) per patient, nonetheless, resulted inferior in the group treated according to the proposed protocol (50,45 • vs. 53,30 •). Furthermore, a lower incidence of complications occurred in these patients. Among the "off-protocol" behaviors, two showed particularly evident misuse of health resources: inappropriate treatment after test positivity (59,15 •/patient), and treatment after test negativity (14% of the total population). Another interesting, although not surprising, result of this study was the evidence that penicillins are as effective as cephalosporins in the short-term, but significantly inferior in terms of complications, positivity for streptococci at the control test, and complications detected at follow-up