8,420 research outputs found

    Microscopic mass estimations

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    The quest to build a mass formula which have in it the most relevant microscopic contributions is analyzed. Inspired in the successful Duflo-Zuker mass description, the challenges to describe the shell closures in a more transparent but equally powerful formalism are discussed.Comment: 14 pages, 6 figures, submitted to Journal of Physics G, Focus issue on Open Problems in Nuclear Structure Theor

    Polarization and readout of coupled single spins in diamond

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    We study the coupling of a single nitrogen-vacancy center in diamond to a nearby single nitrogen defect at room temperature. The magnetic dipolar coupling leads to a splitting in the electron spin resonance frequency of the nitrogen-vacancy center, allowing readout of the state of a single nitrogen electron spin. At magnetic fields where the spin splitting of the two centers is the same we observe a strong polarization of the nitrogen electron spin. The amount of polarization can be controlled by the optical excitation power. We combine the polarization and the readout in time-resolved pump-probe measurements to determine the spin relaxation time of a single nitrogen electron spin. Finally, we discuss indications for hyperfine-induced polarization of the nitrogen nuclear spin

    Network polarization, filter bubbles, and echo chambers: An annotated review of measures and reduction methods

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    Polarization arises when the underlying network connecting the members of a community or society becomes characterized by highly connected groups with weak inter-group connectivity. The increasing polarization, the strengthening of echo chambers, and the isolation caused by information filters in social networks are increasingly attracting the attention of researchers from different areas of knowledge such as computer science, economics, social and political sciences. This work presents an annotated review of network polarization measures and models used to handle the polarization. Several approaches for measuring polarization in graphs and networks were identified, including those based on homophily, modularity, random walks, and balance theory. The strategies used for reducing polarization include methods that propose edge or node editions (including insertions or deletions, as well as edge weight modifications), changes in social network design, or changes in the recommendation systems embedded in these networks.Comment: Corrected a typo in Section 3.2; the rest remains unchange

    On the Nature of Andromeda IV

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    Lying at a projected distance of 40' or 9 kpc from the centre of M31, Andromeda IV is an enigmatic object first discovered during van den Bergh's search for dwarf spheroidal companions to M31. Being bluer, more compact and higher surface brightness than other known dwarf spheroidals, it has been suggested that And IV is either a relatively old `star cloud' in the outer disk of M31 or a background dwarf galaxy. We present deep HST WFPC2 observations of And IV and the surrounding field which, along with ground-based long-slit spectroscopy and Halpha imagery, are used to decipher the true nature of this puzzling object. We find compelling evidence that And IV is a background galaxy seen through the disk of M31. The moderate surface brightness (SB(V)~24), very blue colour (V-I<~0.6), low current star formation rate (~0.001 solar mass/yr) and low metallicity (~10% solar) reported here are consistent with And IV being a small dwarf irregular galaxy, perhaps similar to Local Group dwarfs such as IC 1613 and Sextans A. Although the distance to And IV is not tightly constrained with the current dataset, various arguments suggest it lies in the range 5<~D<~8 Mpc, placing it well outside the confines of the Local Group. It may be associated with a loose group of galaxies, containing major members UGC 64, IC 1727 and NGC 784. We report an updated position and radial velocity for And IV.Comment: 26 pages, LaTex with 9 figures (including 6 jpg plates). Accepted for publication in A

    ENOBIO - First tests of a dry electrophysiology electrode using carbon nanotubes

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    We describe the development and first tests of Enobio, a dry electrode sensor concept for biopotential applications. In the proposed electrodes, the tip of the electrode is covered with a forest of multi-walled CNTs that can be coated with Ag/AgCl to provide ionic-electronic transduction. The CNT brush-like structure is to penetrate the outer layers of the skin improving electrical contact as well as increae the contact surface area. In this paper, we report the results of the first tests of this concept -- immersion on saline solution and pig skin signal detection. These indicate performance on a par with state of the art research-oriented wet electrodes.Comment: Submitted and accepted at the 28th IEEE EMBS International Conference, New York City, August 31st-September 3rd, 2006. Figures updated with proper filtering and averagin

    Pediatric endoscopic pilonidal sinus treatment (PEPSiT): what we learned after a 3-year experience in the pediatric population

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    This paper aimed to report a multi-institutional 3-year experience with pediatric endoscopic pilonidal sinus treatment (PEPSiT) and describe tips and tricks of the technique. We retrospectively reviewed all patients < 18 years, with primary or recurrent pilonidal sinus disease (PSD), undergoing PEPSiT in the period 2017–2020. All patients received pre-operative laser therapy, PEPSiT and post-operative dressing and laser therapy. Success rate, healing rate/time, post-operative management, short- and long-term outcome and patient satisfaction were assessed. A total of 152 patients (98 boys) were included. Median patient’s age was 17.1 years. Fifteen/152 patients (9.8%) presented a recurrent PSD. All patients resumed full daily activities 1 day after surgery. The post-operative course was painless in 100% of patients (median VAS pain score < 2/10). Patient satisfaction was excellent (median score 4.8). The median follow-up was 12.8 months (range 1–36). Complete healing in 8 weeks was achieved in 145/152 (95.4%) and the median healing time was 24.6 days (range 16–31). We reported post-operatively immediate Clavien grade 2 complications (3 oedema, 2 burns) in 5/152 (3.3%) and delayed Clavien grade 2 complications (3 granulomas, 8 wound infections) in 11/152 (7.2%). Disease recurrence occurred in 7/152 (4.6%), who were re-operated using PEPSiT. PEPSiT should be considered the standard of care for surgical treatment of PSD in children and teenagers. PEPSiT is technically easy, with short and painless post-operative course and low recurrence rate (4.6%). Standardized treatment protocol, correct patient enrollment and information, and intensive follow-up are key points for the success of the procedure
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