1,915 research outputs found
Decoupling Transformations in Path Integral Bosonization
We construct transformations that decouple fermionic fields in interaction
with a gauge field, in the path integral representation of the generating
functional. Those transformations express the original fermionic fields in
terms of non-interacting ones, through non-local functionals depending on the
gauge field. This procedure, holding true in any number of spacetime dimensions
both in the Abelian and non-Abelian cases, is then applied to the path integral
bosonization of the Thirring model in 3 dimensions. Knowledge of the decoupling
transformations allows us, contrarily to previous bosonizations, to obtain the
bosonization with an explicit expression of the fermion fields in terms of
bosonic ones and free fermionic fields. We also explain the relation between
our technique, in the two dimensional case, and the usual decoupling in 2
dimensions.Comment: 22 pages, Late
A model for lopsided galactic disks
Many disk galaxies are lopsided: their brightest inner parts are displaced
from the center of the outer isophotes, or the outer contours of the HI disk.
This asymmetry is particularly common in small, low-luminosity galaxies. We
argue here that long-lived lopsidedness is a consequence of the disk lying
off-center in the potential of the galaxy's extended dark halo, and spinning in
a sense retrograde to its orbit about the halo center. The stellar velocity
field predicted by our gravitational N-body simulations is clearly asymmetric.Comment: 10 pages and 2 figures, AASTEX (aaspp4), to appear in ApJ
Exploration of Large Digital Sky Surveys
We review some of the scientific opportunities and technical challenges posed
by the exploration of the large digital sky surveys, in the context of a
Virtual Observatory (VO). The VO paradigm will profoundly change the way
observational astronomy is done. Clustering analysis techniques can be used to
discover samples of rare, unusual, or even previously unknown types of
astronomical objects and phenomena. Exploration of the previously poorly probed
portions of the observable parameter space are especially promising. We
illustrate some of the possible types of studies with examples drawn from
DPOSS; much more complex and interesting applications are forthcoming.
Development of the new tools needed for an efficient exploration of these vast
data sets requires a synergy between astronomy and information sciences, with
great potential returns for both fields.Comment: To appear in: Mining the Sky, eds. A. Banday et al., ESO Astrophysics
Symposia, Berlin: Springer Verlag, in press (2001). Latex file, 18 pages, 6
encapsulated postscript figures, style files include
Recognition of prior learning at the centre of a national strategy: tensions between professional gains and personal development
This paper focuses on recognition of prior learning as part of a national policy based on
European Union guidelines for lifelong learning, and it explains how recognition of prior
learning has been perceived since it was implemented in Portugal in 2000. Data discussed
are the result of a mixed method research project that surveyed adult learners,
some of whom were interviewed, who successfully completed the recognition of prior
learning process from 2007 to 2011 in a new opportunities centre. Adult educators, and
workplace representatives from the companies in which these adults in the recognition
of prior learning process were working, were also part of the survey. A theme-based
content analysis was done on the resulting data. Findings revealed tension between the
goals of economic and human resource management and the change experienced by
these adult learners in their professional status. Based on these results, the closing
remarks to this article highlight the tensions caused by the failure of the goals of the
policy to which recognition of prior learning was central, and the personal and social
changes referred to by learners. Important educational changes were achieved although they were undermined by the adult education policy and European Union guidelines.The writing of this article was funded by Cied – Institute of Education, University of Minho and the Unidade de Investigação e Desenvolvimento em Educação e Formação, Instituto de Educação, Universidade de Lisboa
Investigation Into the Humaneness of Slaughter Methods for Guinea Pigs (Cavia porcelus) in the Andean Region
Guinea pigs (Cavia porcelus) are an important source of nonhuman animal protein in the Andean region of South America. Specific guidelines regarding the welfare of guinea pigs before and during slaughter have yet to be developed. This study critically assessed the humaneness of 4 different stunning/slaughter methods for guinea pigs: cervical neck dislocation (n = 60), electrical head-only stunning (n = 83), carbon dioxide (CO(2)) stunning (n = 21), and penetrating captive bolt (n = 10). Following cervical neck dislocation, 97% of guinea pigs had at least 1 behavioral or cranial/spinal response. Six percent of guinea pigs were classified as mis-stunned after electrical stunning, and 1% were classified as mis-stunned after captive bolt. Increased respiratory effort was observed during CO(2) stunning. Apart from this finding, there were no other obvious behavioral responses that could be associated with suffering. Of the methods assessed, captive bolt was deemed the most humane, effective, and practical method of stunning guinea pigs. Cervical neck dislocation should not be recommended as a slaughter method for guinea pigs
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