8,320 research outputs found
Comment on "Two Phase Transitions in the Fully frustrated XY Model"
The conclusions of a recent paper by Olsson (Phys. Rev. Lett. 75, 2758
(1995), cond-mat/9506082) about the fully frustrated XY model in two dimensions
are questioned. In particular, the evidence presented for having two separate
chiral and U(1) phase transitions are critically considered.Comment: One page one table, to Appear in Physical Review Letter
Formación docente : un ámbito de encuentro entre la educación formal y la educación no formal..
Los propósitos que dieron marco a la propuesta se vincularon con: El fortalecimiento de los procesos educativos en el sistema Formal, a partir de la gestión de proyectos interinstitucionales ; El reconocimiento de la Alfabetización Científica como instancia democratizadora del conocimiento lo cual permite enlazar el mundo de la ciencia con prácticas, hábitos, lenguajes y producciones sociales ; El desarrollo de estrategias didácticas que orientan hacia la problematización y complejización de los contenidos curriculares. Se utilizó una metodología cualitativa con organización de colectivos docentes. Las conclusiones obtenidas nos permiten manifestar que este trabajo de articulación es altamente significativo; si bien se requiere extender el período de colectivo para fortalecer el intercambio de los diferentes actores y lograr mejores resultados
Search and characterization of T-type planetary mass candidates in the sigma Orionis cluster
(Abridged) We aim to: i) confirm the presence of methane absorption in S Ori
73 (a T-type member candidate of the sig Orionis cluster, 3 Myr, 352 pc)
through methane imaging; ii) study S Ori 70 and 73 cluster membership via
photometric colors and accurate proper motion analysis; iii) perform a new
search to identify additional T-type sig Orionis member candidates with likely
masses below 7 Mjup. We obtained HAWK-I (VLT) J, H, and CH4off photometry of an
area of 119.15 sq. arcmin in sig Orionis down to Jcomp = 21.7 and Hcomp = 21
mag. Near-infrared data were complemented with optical photometry using images
acquired with OSIRIS (GTC) and VISTA as part of the VISTA Orion survey. We
derived proper motions by comparison of the new HAWK-I and VISTA images with
published near-infrared data taken 3.4 - 7.9 yr ago. S Ori 73 has a red
H-CH4off color indicating methane absorption in the H-band and a spectral type
of T4 +/- 1. S Ori 70 displays a redder methane color than S Ori 73 in
agreement with its latter spectral classification. Our proper motion
measurements are larger than the motion of sig Orionis, rendering S Ori 70 and
73 cluster membership uncertain. We identified one new photometric candidate
with J = 21.69 +/- 0.12 mag and methane color consistent with spectral type
greater than T8. S Ori 73 has colors similar to those of T3-T5 field dwarfs,
which in addition to its high proper motion suggests that it is probably a
field dwarf located at 170-200 pc. The origin of S Ori 70 remains unclear: it
can be a field, foreground mid- to late-T free-floating dwarf with peculiar
colors, or an orphan planet ejected through strong dynamical interactions from
sig Orionis or from a nearby star-forming region in Orion.Comment: Accepted for publication in A&
Formación docente : un ámbito de encuentro entre la educación formal y la educación no formal
Los propósitos que dieron marco a la propuesta se vincularon con: El fortalecimiento de los procesos educativos en el sistema Formal, a partir de la gestión de proyectos interinstitucionales ; El reconocimiento de la Alfabetización Científica como instancia democratizadora del conocimiento lo cual permite enlazar el mundo de la ciencia con prácticas, hábitos, lenguajes y producciones sociales ; El desarrollo de estrategias didácticas que orientan hacia la problematización y complejización de los contenidos curriculares. Se utilizó una metodología cualitativa con organización de colectivos docentes. Las conclusiones obtenidas nos permiten manifestar que este trabajo de articulación es altamente significativo; si bien se requiere extender el período de colectivo para fortalecer el intercambio de los diferentes actores y lograr mejores resultados
ESÓFAGO DE BARRETT: REVISIÓN DE LA LITERATURA
RESUMENEl Esófago de Barrett (EB) es una patología adquirida producto del reflujo gastroesofágico crónico que provoca la lesión de la mucosa esofágica normal y su reemplazo por mucosa metaplásica. La importancia clínica del EB radica en que constituye un factor de riesgo para el desarrollo de adenocarcinoma esofágico. La incidencia del adenocarcinoma esofágico se encuentra en aumento y su diagnóstico se realiza generalmente en etapas avanzadas, teniendo un pronóstico sombrío. Actualmente el objetivo es detectar el cáncer en etapas iniciales y eventualmente tratables, para lo cual se han planteado distintos protocolos de vigilancia y numerosas alternativas de tratamiento del epitelio metaplásico del esófago de Barrett. En el siguiente artículo se revisan los conceptos más recientes de manejo.SUMMARYBarrett's esophagus is an acquired disease caused by chronic gastroesophageal reflux causing the injury of normal esophageal mucosa and its replacement by metaplastic mucosa. The clinical significance of Barrett's esophagus is that it constitutes a risk factor for the development of esophageal adenocarcinoma. The incidence of esophageal adenocarcinoma is increasing and its diagnosis is usually done in advanced stages, with grim prognosis. Currently the goal is to detect cancer in early, treatable stages. Different protocols have been proposed, numerous alternatives for monitoring and treating metaplastic epithelium of Barrett's esophagus. In the following article the latest management concepts are reviewed
On the and Photoproduction Beam Asymmetry at High Energies
We show that, in the Regge limit, beam asymmetries in and
photoproduction are sensitive to hidden strangeness components. Under
reasonable assumptions about the couplings we estimate the contribution of the
Regge pole, which is expected to be the dominant hidden strangeness
contribution. The ratio of the asymmetries in and production is
estimated to be close to unity in the forward region at the photon energy ~GeV, relevant for the upcoming
measurements at Jefferson Lab.Comment: 9 pages, 4 figure
Type II see-saw dominance in SO(10)
Grand unified theories where the neutrino mass is given by Type II seesaw
have the potential to provide interesting connections between the neutrino and
charged fermion sectors. We explore the possibility of having a dominant Type
II seesaw contribution in supersymmetric SO(10). We show that this can be
achieved in the model where symmetry breaking is triggered by 54 and
45-dimensional representations, without the need for additional fields other
than those already required to have a realistic charged fermion mass spectrum.
Physical consequences, such as the implementation of the BSV mechanism, the
possibility of the fields responsible for Type II see-saw dominance being
messengers of supersymmetry breaking, and the realization of baryo and
leptogenesis in this theories are discussed.Comment: 14 pages, 3 figures. New version with references adde
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