8,420 research outputs found
Microscopic mass estimations
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
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
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
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
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
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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