1,720 research outputs found
A new modulation technique for high data rate low power UWB wireless optical communication in implantable biotelemetry systems
We report on the development of a novel modulation technique for UWB wireless optical communication systems for application in a transcutaneous biotelemetry. The solution, based on the generation of short laser pulses, allows for a high data rate link whilst achieving a significant power reduction (energy per bit) compared to the state-of-the-art. These features make this particularly suitable for emerging biomedical applications such as implantable neural/biosensor systems. The relatively simple architecture consists of a transmitter and receiver that can be integrated in a standard CMOS technology in a compact Silicon footprint. These parts include circuits for bias and drive current generation, conditioning and processing, optimised for low-volt age/low-power operation. Preliminary experimental findings validate the new paradigm and show good agreement with expected results. The complete system achieves a BER less than 10-7, with maximum data rate of 125Mbps and estimated total power consumption of less than 3mW
The rare case of positive FDG-positron emission tomography for giant cavernous hemangioma of the liver
Hemangioma is the most common benign liver tumor and the second most common liver tumor after metastases. Large hemangiomas are often heterogeneous. When they exceed 4 cm in diameter, they are termed giant hemangiomas. These giant hemangiomas often present heterogeneous patterns. These heterogeneous appearances are shown because of intratumoral changes due to several
degenerative phenomena. PET/CT is reported to be useful for the differentiation of benign from malignant liver lesions. We report the case of a large hepatic hemangioma characterized by high FDG uptake
Where Fail-Safe Default Logics Fail
Reiter's original definition of default logic allows for the application of a
default that contradicts a previously applied one. We call failure this
condition. The possibility of generating failures has been in the past
considered as a semantical problem, and variants have been proposed to solve
it. We show that it is instead a computational feature that is needed to encode
some domains into default logic
On the magnetic structure and wind parameter profiles of Alfven wave driven winds in late-type supergiant stars
Cool stars at giant and supergiant evolutionary phases present low velocity
and high density winds, responsible for the observed high mass-loss rates.
Although presenting high luminosities, radiation pressure on dust particles is
not sufficient to explain the wind acceleration process. Among the possible
solutions to this still unsolved problem, Alfven waves are, probably, the most
interesting for their high efficiency in transfering energy and momentum to the
wind. Typically, models of Alfven wave driven winds result in high velocity
winds if they are not highly damped. In this work we determine
self-consistently the magnetic field geometry and solve the momentum, energy
and mass conservation equations, to demonstrate that even a low damped Alfven
wave flux is able to reproduce the low velocity wind. We show that the magnetic
fluxtubes expand with a super-radial factor S>30 near the stellar surface,
larger than that used in previous semi-empirical models. The rapid expansion
results in a strong spatial dilution of the wave flux. We obtained the wind
parameter profiles for a typical supergiant star of 16 M_sun. The wind is
accelerated in a narrow region, coincident with the region of high divergence
of the magnetic field lines, up to 100 km/s. For the temperature, we obtained a
slight decrease near the surface for low damped waves, because the wave heating
mechanism is less effective than the radiative losses. The peak temperature
occurs at 1.5 r_0 reaching 6000 K. Propagating outwards, the wind cools down
mainly due to adiabatic expansion.Comment: to appear in the MNRA
Methods and approaches for blind test predictions of out-of-plane behavior of masonry walls: a numerical comparative study
Earthquakes cause severe damage to masonry structures due to inertial forces acting in the normal direction to the plane of the walls. The out-of-plane behavior of masonry walls is complex and depends on several parameters, such as material and geometric properties of walls, connections between structural elements, the characteristics of the input motions, among others. Different analytical methods and advanced numerical modeling are usually used for evaluating the out-of-plane behavior of masonry structures. Furthermore, different types of structural analysis can be adopted for this complex behavior, such as limit analysis, pushover, or nonlinear dynamic analysis.Aiming to evaluate the capabilities of different approaches to similar problems, blind predictions were made using different approaches. For this purpose, two idealized structures were tested on a shaking table and several experts on masonry structures were invited to present blind predictions on the response of the structures, aiming at evaluating the available tools for the out-of-plane assessment of masonry structures. This article presents the results of the blind test predictions and the comparison with the experimental results, namely in terms of formed collapsed mechanisms and control outputs (PGA or maximum displacements), taking into account the selected tools to perform the analysis.info:eu-repo/semantics/publishedVersio
In-flight validation of Metis Visible-light Polarimeter Coronagraph on board Solar Orbiter
Context. The Metis coronagraph is one of the remote-sensing instruments of
the ESA/NASA Solar Orbiter mission. Metis is aimed at the study of the solar
atmosphere and solar wind by simultaneously acquiring images of the solar
corona at two different wavelengths; visible-light (VL) within a band ranging
from 580 nm to 640 nm, and in the HI Ly-alpha 121.6 +/- 10 nm ultraviolet (UV)
light. The visible-light channel includes a polarimeter with electro-optically
modulating Liquid Crystal Variable Retarders (LCVRs) to measure the linearly
polarized brightness of the K-corona to derive the electron density.
Aims. In this paper, we present the first in-flight validation results of the
Metis polarimetric channel together with a comparison to the on-ground
calibrations. It is the validation of the first use in deep space (with hard
radiation environment) of an electro-optical device: a liquid crystal-based
polarimeter.
Methods. We used the orientation of the K-corona's linear polarization vector
during the spacecraft roll maneuvers for the in-flight calibration.
Results. The first in-flight validation of the Metis coronagraph on-board
Solar Orbiter shows a good agreement with the on-ground measurements. It
confirms the expected visible-light channel polarimetric performance. A final
comparison between the first pB obtained by Metis with the polarized brightness
(pB) obtained by the space-based coronagraph LASCO and the ground-based
coronagraph KCor shows the consistency of the Metis calibrated results.Comment: 8 pages, 13 figures, 3 tables, pape
Performance and science reach of the Probe of Extreme Multimessenger Astrophysics for ultrahigh-energy particles
The Probe Of Extreme Multi-Messenger Astrophysics (POEMMA) is a potential
NASA Astrophysics Probe-class mission designed to observe ultra-high energy
cosmic rays (UHECRs) and cosmic neutrinos from space. POEMMA will monitor
colossal volumes of the Earth's atmosphere to detect extensive air showers
(EASs) produced by extremely energetic cosmic messengers: UHECRs above 20 EeV
over the full sky and cosmic neutrinos above 20 PeV. We focus most of this
study on the impact of POEMMA for UHECR science by simulating the detector
response and mission performance for EAS from UHECRs. We show that POEMMA will
provide a significant increase in the statistics of observed UHECRs at the
highest energies over the entire sky. POEMMA will be the first UHECR
fluorescence detector deployed in space that will provide high-quality
stereoscopic observations of the longitudinal development of air showers.
Therefore, it will be able to provide event-by-event estimates of the
calorimetric energy and nuclear mass of UHECRs. The particle physics in the
interactions limits the interpretation of the shower maximum on an event by
event basis. In contrast, the calorimetric energy measurement is significantly
less sensitive to the different possible final states in the early
interactions. We study the prospects to discover the origin and nature of
UHECRs using expectations for measurements of the energy spectrum, the
distribution of arrival direction, and the atmospheric column depth at which
the EAS longitudinal development reaches maximum. We also explore supplementary
science capabilities of POEMMA through its sensitivity to particle interactions
at extreme energies and its ability to detect ultra-high energy neutrinos and
photons produced by top-down models including cosmic strings and super-heavy
dark matter particle decay in the halo of the Milky Way.Comment: 40 pages revtex, with 42 figure
Unexpectedly high pressure for molecular dissociation in liquid hydrogen by electronic simulation
The study of the high pressure phase diagram of hydrogen has continued with renewed effort for about one century as it remains a fundamental challenge for experimental and theoretical techniques. Here we employ an efficient molecular dynamics based on the quantum Monte Carlo method, which can describe accurately the electronic correlation and treat a large number of hydrogen atoms, allowing a realistic and reliable prediction of thermodynamic properties. We find that the molecular liquid phase is unexpectedly stable, and the transition towards a fully atomic liquid phase occurs at much higher pressure than previously believed. The old standing problem of low-temperature atomization is, therefore, still far from experimental reach
Does Turbulence along the Coronal Current Sheet Drive Ion Cyclotron Waves?
Evidence for the presence of ion cyclotron waves (ICWs), driven by turbulence, at the boundaries of the current sheet is reported in this paper. By exploiting the full potential of the joint observations performed by Parker Solar Probe and the Metis coronagraph on board Solar Orbiter, local measurements of the solar wind can be linked with the large-scale structures of the solar corona. The results suggest that the dynamics of the current sheet layers generates turbulence, which in turn creates a sufficiently strong temperature anisotropy to make the solar-wind plasma unstable to anisotropy-driven instabilities such as the Alfvén ion cyclotron, mirror-mode, and firehose instabilities. The study of the polarization state of high-frequency magnetic fluctuations reveals that ICWs are indeed present along the current sheet, thus linking the magnetic topology of the remotely imaged coronal source regions with the wave bursts observed in situ. The present results may allow improvement of state-of-the-art models based on the ion cyclotron mechanism, providing new insights into the processes involved in coronal heating
Breakthrough SARS-CoV-2 infections after COVID-19 mRNA vaccination in MS patients on disease modifying therapies during the Delta and the Omicron waves in Italy
Background In this study we aimed to monitor the risk of breakthrough SARS-CoV-2 infection in patients with MS (pwMS) under different DMTs and to identify correlates of reduced protection.Methods This is a prospective Italian multicenter cohort study, long-term clinical follow-up of the CovaXiMS (Covid-19 vaccine in Multiple Sclerosis) study. 1855 pwMS scheduled for SARS-CoV-2 mRNA vaccination were enrolled and followed up to a mean time of 10 months. The cumulative incidence of breakthrough Covid-19 cases in pwMS was calculated before and after December 2021, to separate the Delta from the Omicron waves and to account for the advent of the third vaccine dose.Findings 1705 pwMS received 2 m-RNA vaccine doses, 21/28 days apart. Of them, 1508 (88.5%) had blood assessment 4 weeks after the second vaccine dose and 1154/1266 (92%) received the third dose after a mean interval of 210 days (range 90-342 days) after the second dose. During follow-up, 131 breakthrough Covid-19 infections (33 during the Delta and 98 during the Omicron wave) were observed. The probability to be infected during the Delta wave was associated with SARS-CoV-2 antibody levels measured after 4 weeks from the second vaccine dose (HR=0.57, p < 0.001); the protective role of antibodies was preserved over the whole follow up (HR=0.57, 95%CI=0.43-0.75, p < 0.001), with a significant reduction (HR=1.40, 95%CI=1.01-1.94, p=0.04) for the Omicron cases. The third dose significantly reduced the risk of infection (HR=0.44, 95%CI=0.21-0.90,p=0.025) during the Omicron wave.Interpretation The risk of breakthrough SARS-CoV-2 infections is mainly associated with reduced levels of the virus-specific humoral immune response. Copyright (c) 2022 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/
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