499 research outputs found
Hallazgos electromiográficos y electroneurográficos en el pie cavo esencial
La etiologĂa del pie cavo cuando Ă©sta es conocida, suele ser debida a un trastorno
de tipo neurológico o miopático, aunque en determinados casos nos encontramos con pacientes
que padecen esta deformidad en el pie, en los cuales no podemos descubrir ningĂşn
antecedente de este tipo, por lo que lo calificamos de pie cavo «esencial». A un grupo de estos
pacientes con pie cavo «esencial», en los que no hemos encontrado ningún tipo de antecedente
neurológico, lo hemos sometido a una exploración electroneurográfica, encontrando que la
mitad de ellos padecĂan algĂşn trastorno neuropático/miopático, que no habĂa sido detectado
en la exploraciĂłn clĂnica inicial.Neurological or myopathic diseases are frequently involved in the etiology of flat
foot. In some cases, no antecedents of disease can be found and therefore these flat foots are
classified as «essential». We have undertaken an electrophysiologic study in a series of patients
with «essential» flat food in order to explore unsuspected neurological disorders. In half of the
patients, neuropathic and myopathic electroneurographic patterns of different severity were detected
Carbon and oxygen abundances from recombination lines in low-metallicity star-forming galaxies. Implications for chemical evolution
We present deep echelle spectrophotometry of the brightest emission-line
knots of the star-forming galaxies He 2-10, Mkn 1271, NGC 3125, NGC 5408, POX
4, SDSS J1253-0312, Tol 1457-262, Tol 1924-416 and the HII region Hubble V in
the Local Group dwarf irregular galaxy NGC 6822. The data have been taken with
the Very Large Telescope Ultraviolet-Visual Echelle Spectrograph in the
3100-10420 {\AA} range. We determine electron densities and temperatures of the
ionized gas from several emission-line intensity ratios for all the objects. We
derive the ionic abundances of C and/or O from faint pure
recombination lines (RLs) in several of the objects, permitting to derive their
C/H and C/O ratios. We have explored the chemical evolution at low
metallicities analysing the C/O vs. O/H, C/O vs. N/O and C/N vs. O/H relations
for Galactic and extragalactic HII regions and comparing with results for halo
stars and DLAs. We find that HII regions in star-forming dwarf galaxies occupy
a different locus in the C/O vs. O/H diagram than those belonging to the inner
discs of spiral galaxies, indicating their different chemical evolution
histories, and that the bulk of C in the most metal-poor extragalactic HII
regions should have the same origin than in halo stars. The comparison between
the C/O ratios in HII regions and in stars of the Galactic thick and thin discs
seems to give arguments to support the merging scenario for the origin of the
Galactic thick disc. Finally, we find an apparent coupling between C and N
enrichment at the usual metallicities determined for HII regions and that this
coupling breaks in very low-metallicity objects.Comment: 27 pages, 12 figures, Accepted for publication in Monthly Notices of
the Royal Astronomical Societ
Integral field spectroscopy of selected areas of the Bright Bar and Orion-S cloud in the Orion Nebula
We present integral field spectroscopy of two selected zones in the Orion
Nebula obtained with the Potsdam Multi-Aperture Spectrophotometer (PMAS),
covering the optical spectral range from 3500 to 7200 A and with a spatial
resolution of 1". The observed zones are located on the prominent Bright Bar
and on the brightest area at the northeast of the Orion South cloud, both
containing remarkable ionization fronts. We obtain maps of emission line fluxes
and ratios, electron density and temperatures, and chemical abundances. We
study the ionization structure and morphology of both fields, which ionization
fronts show different inclination angles with respect to the plane of the sky.
We find that the maps of electron density, O+/H+ and O/H ratios show a rather
similar structure. We interpret this as produced by the strong dependence on
density of the [OII] lines used to derive the O+ abundance, and that our
nominal values of electron density-derived from the [SII] line ratio-may be
slightly higher than the appropriate value for the O+ zone. We measure the
faint recombination lines of OII in the field at the northeast of the Orion
South cloud allowing us to explore the so-called abundance discrepancy problem.
We find a rather constant abundance discrepancy across the field and a mean
value similar to that determined in other areas of the Orion Nebula, indicating
that the particular physical conditions of this ionization front do not
contribute to this discrepancy.Comment: 15 pages, 10 figures. Accepted for publication in MNRA
Carbon and oxygen in HII regions of the Magellanic Clouds: abundance discrepancy and chemical evolution
We present C and O abundances in the Magellanic Clouds derived from deep
spectra of HII regions. The data have been taken with the Ultraviolet-Visual
Echelle Spectrograph at the 8.2-m VLT. The sample comprises 5 HII regions in
the Large Magellanic Cloud (LMC) and 4 in the Small Magellanic Cloud (SMC). We
measure pure recombination lines (RLs) of CII and OII in all the objects,
permitting to derive the abundance discrepancy factors (ADFs) for O^2+, as well
as their O/H, C/H and C/O ratios. We compare the ADFs with those of other HII
regions in different galaxies. The results suggest a possible metallicity
dependence of the ADF for the low-metallicity objects, but more uncertain for
high-metallicity objects. We compare nebular and B-type stellar abundances and
we find that the stellar abundances agree better with the nebular ones derived
from collisionally excited lines (CELs). Comparing these results with other
galaxies we observe that stellar abundances seem to agree better with the
nebular ones derived from CELs in low-metallicity environments and from RLs in
high-metallicity environments. The C/H, O/H and C/O ratios show almost flat
radial gradients, in contrast with the spiral galaxies where such gradients are
negative. We explore the chemical evolution analysing C/O vs. O/H and comparing
with the results of HII regions in other galaxies. The LMC seems to show a
similar chemical evolution to the external zones of small spiral galaxies and
the SMC behaves as a typical star-forming dwarf galaxy.Comment: Accepted for publication in MNRAS, 17 pages, 11 figures, 8 table
Properties of the ionized gas in HH202. I: Results from integral field spectroscopy with PMAS
We present results from integral field spectroscopy with the Potsdam
multi-Aperture Spectrograph of the head of the Herbig-Haro object HH 202 with a
spatial sampling of 1"x1". We have obtained maps of different emission lines,
physical conditions --such as electron temperature and density-- and ionic
abundances from recombination and collisionally excited lines. We present the
first map of the Balmer temperature and of the temperature fluctuation
parameter, t^2. We have calculated the t^2 in the plane of the sky, which is
substantially smaller than that determined along the line of sight. We have
mapped the abundance discrepancy factor of O^{2+}, ADF(O^{2+}), finding its
maximum value at the HH 202-S position. We have explored the relations between
the ADF(O^{2+}) and the electron density, the Balmer and [O III] temperatures,
the ionization degree as well as the t^2 parameter. We do not find clear
correlations between these properties and the results seem to support that the
ADF and t^2 are independent phenomena. We have found a weak negative
correlation between the O^{2+} abundance determined from recombination lines
and the temperature, which is the expected behaviour in an ionized nebula,
hence it seems that there is not evidence for the presence of super-metal rich
droplets in H II regions.Comment: 12 pages, 11 figures. Accepted for publication in MNRA
GRASP algorithms for the robust railway network design problem
This paper analyzes the solvability of a railway network design problem and its robust version. These problems are modeled as integer linear programming problems with binary variables, and their solutions provide topological railway networks maximizing the trip coverage in the presence of a competing mode, both assuming that the network works fine and that links can fail, respectively. Since these problems are computationally intractable for realistic sizes, GRASP heuristics are proposed for finding good feasible solutions. The results obtained in a computational experience indicate that our GRASP algorithms are suitable for railway network design problems. © 2011 Springer Science+Business Media, LLC.We would like to thank the Spanish Ministerio de Fomento under grant PT-2007-003, Ministerio de Ciencia y Educacion under grant MTM2009-14243, the Junta de Andalucia under grant P09-TEP-5022 for supporting this research, the FEDER funds of the European Union and TUSSAM (Seville, Spain). Special thanks are due to two anonymous referees for their valuable comments.GarcĂa-Archilla, B.; Lozano, AJ.; Mesa, JA.; Perea Rojas Marcos, F. (2011). GRASP algorithms for the robust railway network design problem. Journal of Heuristics. 19(2):399-422. https://doi.org/10.1007/s10732-011-9185-zS399422192Baaj, M., Mahmassani, H.: An AI-based approach for transit route system planning and design. J. Adv. Transp. 25(2), 187–210 (1991)Cancela, H., Robledo, F., Rubino, G.: A grasp algorithm with tree based local search for designing a survivable wide area network backbone. J. Comput. Sci. Technol. 4(1), 52–58 (2004)DĂaz, J.A., Luna, D., Luna, R.: A grasp heuristic for the manufacturing cell formation problem. TOP (2011). doi: 10.1007/s11750-010-0159-3Feo, T., Resende, M.: A probabilistic heuristic for a computationally difficult set covering problem. Oper. Res. Lett. 8, 67–71 (1989)Goossens, J., van Hoesel, C., Kroon, L.: A branch-and-cut approach for solving railway line-planning problems. Transp. Sci. 38, 379–393 (2004)Institute of Electrical and Electronics Engineers: IEEE Standard Computer Dictionary: A Compilation of IEEE Standard Computer Glossaries (1990)Laporte, G., Mesa, J., Perea, F.: A game theoretic framework for the robust railway transit network design problem. Transp. Res., Part B, Methodol. 44, 447–459 (2010)Laporte, G., MarĂn, A., Mesa, J., Perea, F.: Designing robust rapid transit networks with alternative routes. J. Adv. Transp. 45, 54–65 (2011)MarĂn, A., GarcĂa-RĂłdenas, R.: Location of infrastructure in urban railway networks. Comput. Oper. Res. 36, 1461–1477 (2009)MarĂn, A., Jaramillo, P.: Urban rapid transit network design: accelerated Benders decomposition. Ann. Oper. Res. 169(1), 35–53 (2009)MarĂn, A., Mesa, J.A., Perea, F.: Integrating robust railway network design and line planning under failures. Lect. Notes Comput. Sci. 5868, 273–292 (2009)Mauttone, A., Urquhart, M.E.: A route set construction algorithm for the transit network design problem. Comput. Oper. Res. 36, 2440–2449 (2009)Murphey, R., Pardalos, P., Pitsoulis, L.: A GRASP for the multitarget multisensor tracking problem. In: Networks. Discrete Mathematics and Theoretical Computer Science Series, vol. 40, pp. 277–302. American Mathematical Society, Providence (1998)Nesmachnow, S., Cancela, H., Alba, E.: Evolutionary algorithms applied to reliable communication network design. Eng. Optim. 39(7), 831–855 (2007)Schöbel, A., Scholl, S.: Line planning with minimal transfers. In: 5th Workshop on Algorithmic Methods and Models for Optimization of Railways, Number 06901 in Dagstuhl Seminar Proceedings (2006
Sinovitis villonodular pigmentada difusa: RevisiĂłn de 13 casos
Se hace un estudio retrospectivo de trece pacientes con Sinovitis Villonodular pigmentada, seis localizadas en la rodilla, dos en la muñeca y pie, y uno en tobillo, cadera y codo respectivamente. En cinco de los casos existĂa una afectaciĂłn del hueso. Se hace una revisiĂłn bibliográfica sobre la etiopatogenia, radiologĂa, mĂ©todos diagnĂłsticos y tratamientoA retrospective study of thirteen patients with pigmented villonodular synovitis was made. Six cases were localized in the knee, two in the wrist and feet, and one in ankle, hip and elbow. Five case showed bone invasion, the pathogenesis, radiographical appearance, diagnosis and treatment are discussed
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