Hybrid CFRP-based strengthening technique to increase the flexural resistance and concrete confinement of RC columns submitted to axial and cyclic lateral loading

A strengthening technique that combines carbon fibre reinforced polymer (CFRP) laminates and strips of wet lay-up CFRP sheet was used to increase the flexural resistance and the energy dissipation capacity of square cross-section columns of very low concrete strength submitted to constant axial compressive force and cyclic lateral loading. The laminates, applied according to the Near Surface Mounted (NSM) technique, have the purpose of increasing the flexural resistance of the columns, while the CFRP sheet installed as a localized jacket in the plastic hinge has the aim of increasing the concrete confinement and avoid the buckling and the debonding of the laminates. In spite of the 8 MPa of average concrete compressive strength used to manufacture the columns, the hybrid strategy provided an average increase of about 46 % in terms of load carrying capacity, even when applied in columns that had already been tested and presented intensives damages. The experimental program is described and the main results are presented and analyzed

Kelvin-Helmholtz instability at proton scales with an exact kinetic equilibrium

The Kelvin-Helmholtz instability is a ubiquitous physical process in ordinary fluids and plasmas, frequently observed also in space environments. In this paper, kinetic effects at proton scales in the nonlinear and turbulent stage of the Kelvin-Helmholtz instability have been studied in magnetized collisionless plasmas by means of Hybrid Vlasov-Maxwell simulations. The main goal of this work is to point out the back reaction on particles triggered by the evolution of such instability, as energy reaches kinetic scales along the turbulent cascade. Interestingly, turbulence is inhibited when Kelvin-Helmholtz instability develops over an initial state which is not an exact equilibrium state. On the other hand, when an initial equilibrium condition is considered, energy can be efficiently transferred towards short scales, reaches the typical proton wavelengths and drives the dynamics of particles. As a consequence of the interaction of particles with the turbulent fluctuating fields, the proton velocity distribution deviates significantly from the local thermodynamic equilibrium, the degree of deviation increasing with the level of turbulence in the system and being located near regions of strong magnetic stresses. These numerical results support recent space observations from the Magnetospheric MultiScale mission of ion kinetic effects driven by the turbulent dynamics at the Earth's magnetosheath (Perri et al., 2020, JPlPh, 86, 905860108) and by the Kelvin-Helmholtz instability in the Earth's magnetosphere (Sorriso-Valvo et al., 2019, PhRvL, 122, 035102).Comment: 14 pages, 11 figure

Comparative leaf micromorphology, anatomy and architecture in some Mediterranean species of Pancratium (Amaryllidaceae)

Leaves in Pancratium show a gross morphological identity. Difference at macroscopic level also regards leaf tip (acute to obtuse) and lamina width. Despite such uniformity of the leaf visible traits, micro-morphological and anatomical characteristics reveal significant variation both at intra-specific and inter-specific levels, which have proven to strongly depend on adaptation to microclimatic and ecological local conditions, such as temperature, water availability, insolation. Here we present preliminary results of a comparative morpho-anatomical study on leaves of some species of Pancratium (P. foetidum Pomel, P. illyricum L., P. linosae Soldano & F. Conti, P. maritimum L., P. sickenbergeri Boiss.) to assess the range of inter-specific variation, as well as population similarity or dissimilarity related to ecological adaptation

Effects of regional systolic asynchrony on left ventricular global diastolic function in patients with coronary artery disease

AbstractPatients with coronary artery disease often have impaired left ventricular diastolic filling despite normal global systolic function. The influence of regional systolic asynchrony on diastolic function was assessed by radionuclide angiography in 60 patients with coronary artery disease and normal ejection fraction at rest: group 1 (n = 30) with normal wall motion at rest and group 2 (n = 30) with abnormal wall motion. Data were compared with those obtained from 19 normal volunteers.Age, heart rate, ejection fraction and echocardiographic enddiastolic dimension did not differ among the three groups. Peak filling rate in group 1 and group 2 was similar (2.5 ± 0.5 and 2.3 ± 0.6 end-diastolic counts/s, respectively) and significantly lower than that in the normal subjects (2.8 ± 0.7 end-diastolic counts/s; p < 0.01 vs. group 2, p < 0.05 vs. group 1). Time to peak filling rate was prolonged in group 2 (184 ± 27 ms) compared with that in normal subjects (162 ± 19 ms; p < 0.01) and group 1 (172 ± 15 ms; p < 0.05). Left ventricular end-diastolic pressure was significantly higher in group 2 than in group 1 (14 ± 7 vs. 10 ± 5 mm Hg, respectively; p < 0.05).Asynchrony was assessed by sector analysis of the radionuclide left ventricular region of interest. Diastolic asynchrony was similar in the two patient groups (30 ± 23 ms in group 2, 26 ± 16 ms in group 1) and was higher in both groups than in the normal subjects (16 ± 8 ms; p < 0.61). However, systolic asynchrony was higher in group 2 (32 ± 15 ms) than in both group 1 (14 ± 6 ms; p < 0.01) and the normal group (9 ± 6 ms; p < 0.01). In the total group of patients with coronary artery disease, systolic asynchrony correlated with global time to peak filling rate (r = 0.53; p < 0.001). This correlation became stronger when only group 2 was considered (r = 9.62; p < 0.001). Moreover, in group 2 systolic asynchrony correlated with the duration of the isovolumetric relaxation period (r = 0.58; p < 0.001) and the isovolumetric relaxation period, in turn, correlated with global time to peak filling rate (r = 0.72; p < 0.001).Thus, left ventricular systolic asynchrony affects both the relaxation and filling phases of diastole, thereby contributing to the impairment of diastolic function commonly observed in patients with coronary artery disease

Self-Organized Criticality model for Brain Plasticity

Networks of living neurons exhibit an avalanche mode of activity, experimentally found in organotypic cultures. Here we present a model based on self-organized criticality and taking into account brain plasticity, which is able to reproduce the spectrum of electroencephalograms (EEG). The model consists in an electrical network with threshold firing and activity-dependent synapse strenghts. The system exhibits an avalanche activity power law distributed. The analysis of the power spectra of the electrical signal reproduces very robustly the power law behaviour with the exponent 0.8, experimentally measured in EEG spectra. The same value of the exponent is found on small-world lattices and for leaky neurons, indicating that universality holds for a wide class of brain models.Comment: 4 pages, 3 figure

Earth-skimming UHE Tau Neutrinos at the Fluorescence Detector of Pierre Auger Observatory

Ultra high energy neutrinos are produced by the interaction of hadronic cosmic rays with the cosmic radiation background. More exotic scenarios like topological defects or new hadrons predict even larger fluxes. In particular, Earth-skimming tau neutrinos could be detected by the Fluorescence Detector (FD) of Pierre Auger Observatory. A detailed evaluation of the expected number of events has been performed for a wide class of neutrino flux models. An updated computation of the neutrino-nucleon cross section and of the tau energy losses has been carried out. For the most optimistic theoretical models, about one Earth-skimming neutrino event is expected in several years at FD.Comment: 26 pages, 13 figures, version accepted for publication on Astroparticle Physic

Local energy transfer rate and kinetic processes: the fate of turbulent energy in two-dimensional Hybrid Vlasov-Maxwell numerical simulations

The nature of the cross-scale connections between the inertial range turbulent energy cascade and the small-scale kinetic processes in collisionless plasmas is explored through the analysis of two-dimensional Hybrid Vlasov-Maxwell numerical simulation (HVM), with α particles, and through a proxy of the turbulent energy transfer rate, namely the Local Energy Transfer rate (LET). Correlations between pairs of variables, including those related to kinetic processes and to deviation from Maxwellian distributions, are first evidenced. Then, the general properties and the statistical scaling laws of the LET are described, confirming its reliability for the description of the turbulent cascade and revealing its textured topology. Finally, the connection between such proxy and the diag- nostic variables is explored using conditional averaging, showing that several quantities are enhanced in the presence of large positive energy flux, and reduced near sites of neg- ative flux. These observations can help determining which processes are involved in the dissipation of energy at small scales, as for example ion-cyclotron or mirror instabilities typically associated with perpendicular anisotropy of temperature

Variability of the Magnetic Field Power Spectrum in the Solar Wind at Electron Scales

At electron scales, the power spectrum of solar-wind magnetic fluctuations can be highly variable and the dissipation mechanisms of the magnetic energy into the various particle species is under debate. In this paper, we investigate data from the Cluster mission's STAFF Search Coil magnetometer when the level of turbulence is sufficiently high that the morphology of the power spectrum at electron scales can be investigated. The Cluster spacecraft sample a disturbed interval of plasma where two streams of solar wind interact. Meanwhile, several discontinuities (coherent structures) are seen in the large-scale magnetic field, while at small scales several intermittent bursts of wave activity (whistler waves) are present. Several different morphologies of the power spectrum can be identified: (1) two power laws separated by a break, (2) an exponential cutoff near the Taylor shifted electron scales, and (3) strong spectral knees at the Taylor shifted electron scales. These different morphologies are investigated by using wavelet coherence, showing that, in this interval, a clear break and strong spectral knees are features that are associated with sporadic quasi parallel propagating whistler waves, even for short times. On the other hand, when no signatures of whistler waves at similar to 0.1-0.2f(ce) are present, a clear break is difficult to find and the spectrum is often more characteristic of a power law with an exponential cutoff.Peer reviewe