1,495 research outputs found
"Distance mapping" and the 3-D structure of BB +30 3639
BD +30 3639 is a member of a group of uncommon planetary nebula with
Wolf-Rayet central star and higher expansion velocities in [O III] than in [N
II] lines. Images and high-resolution spectra from the literature are used in
order to construct a 3-D model of the nebula using the morpho-kinematic code
SHAPE. We find that two homologous expansion laws are needed for the [N II] and
[O III] shell. We conclude that the internal velocity field of BD +30 3639
decreases with the distance from the central star at least between the [O III]
and [N II] shells. A cylindrical velocity component is used to replicate the
high-speed bipolar collimated outflows. We also present a new kinematic
analysis technique called "distance mapping". It uses the observed proper
motion vectors and the 3-D velocity field to generate maps that can be used as
a constraint to the morpho-kinematic modeling with SHAPE as well as improve the
accuracy for distance determination. It is applied to BD+30 3639 using 178
internal proper motion vectors from Li et al. (2002) and our 3-D velocity field
to determine a distance of 1.52 \pm 0.21 kpc. Finally, we find evidence for an
interaction between the eastern part of nebula and the ambient H2 molecular
gas.Comment: 11 pages, 12 figures, 1 table, Accepted to MNRA
Reduction of the size of datasets by using evolutionary feature selection: the case of noise in a modern city
Smart city initiatives have emerged to mitigate the negative effects of a very fast growth of urban areas. Most of the population in our cities are exposed to high levels of noise that generate discomfort and different health problems. These issues may be mitigated by applying different smart cities solutions, some of them require high accurate noise information to provide the best quality of serve possible. In this study, we have designed a machine learning approach based on genetic algorithms to analyze noise data captured in the university campus. This method reduces the amount of data required to classify the noise by addressing a feature selection optimization problem. The experimental results have shown that our approach improved the accuracy in 20% (achieving an accuracy of 87% with a reduction of up to 85% on the original dataset).Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.
This research has been partially funded by the Spanish MINECO and FEDER projects TIN2016-81766-REDT (http://cirti.es), and TIN2017-88213-R (http://6city.lcc.uma.es)
A new radiative cooling curve based on an up to date plasma emission code
This work presents a new plasma cooling curve that is calculated using the
SPEX package. We compare our cooling rates to those in previous works, and
implement the new cooling function in the grid-adaptive framework `AMRVAC'.
Contributions to the cooling rate by the individual elements are given, to
allow for the creation of cooling curves tailored to specific abundance
requirements. In some situations, it is important to be able to include
radiative losses in the hydrodynamics. The enhanced compression ratio can
trigger instabilities (such as the Vishniac thin-shell instability) that would
otherwise be absent. For gas with temperatures below 10,000 K, the cooling time
becomes very long and does not affect the gas on the timescales that are
generally of interest for hydrodynamical simulations of circumstellar plasmas.
However, above this temperature, a significant fraction of the elements is
ionised, and the cooling rate increases by a factor 1000 relative to lower
temperature plasmas.Comment: 11 pages, 6 figures. Typos fixed to match version on A&A
'forthcoming' website. Tables in text format online available at
http://www.phys.uu.nl/~schure/coolin
Are Proto-Planetary Nebulae Shaped by a Binary? Results of a Long-Term Radial Velocity Study
The shaping of the nebula is currently one of the outstanding unsolved
problems in planetary nebula (PN) research. Several mechanisms have been
proposed, most of which require a binary companion. However, direct evidence
for a binary companion is lacking in most PNs. We have addressed this problem
by obtaining precise radial velocities of seven bright proto-planetary nebulae
(PPNs), objects in transition from the asymptotic giant branch to the PN phases
of stellar evolution. These have F-G spectral types and have the advantage over
PNs of having more and sharper spectral lines, leading to better precision. Our
observations were made in two observing intervals, 1991-1995 and 2007-2010, and
we have included in our analysis some additional published and unpublished
data. Only one of the PPNs, IRAS 22272+5435, shows a long-term variation that
might tentatively be attributed to a binary companion, with P 22 years, and
from this, limiting binary parameters are calculated. Selection effects are
also discussed. These results set significant restrictions on the range of
possible physical and orbital properties of any binary companions: they have
periods greater than 25 years or masses of brown dwarfs or super-Jupiters.
While not ruling out the binary hypothesis, it seems fair to say that these
results do not support it.Comment: 14 pages, 3 figures, to appear Astrophys J, 734 (2011 June 10
Discovery of magnetic fields in central stars of planetary nebulae
For the first time we have directly detected magnetic fields in central stars
of planetary nebulae by means of spectro-polarimetry with FORS1 at the VLT. In
all four objects of our sample we found kilogauss magnetic fields, in NGC1360
and LSS1362 with very high significance, while in EGB5 and Abell36 the
existence of a magnetic field is probable but with less certainty. This
discovery supports the hypothesis that the non-spherical symmetry of most
planetary nebulae is caused by magnetic fields in AGB stars. Our high discovery
rate demands mechanisms to prevent full conservation of magnetic flux during
the transition to white dwarfs.Comment: 8 pages, 4 figures, Accepted for Publication by Astronomy &
Astrophysics See also press release by A&A on their homepage
www.edpsiences.or
Wolf-Rayet and LBV Nebulae as the Result of Variable and Non-Spherical Stellar Winds
The physical basis for interpreting observations of nebular morphology around
massive stars in terms of the evolution of the central stars is reviewed, and
examples are discussed, including NGC 6888, OMC-1, and eta Carinae.Comment: To be published in the Proceedings of IAU Colloquium 169 on Variable
and Non-Spherical Stellar Winds in Luminous Hot Stars, ed. B. Wolf
(Springer-Verlag, Berlin, Heidelberg). 7 pages, including 5 figures. A
full-resolution version of fig 4 is available in the version at
http://www.mpia-hd.mpg.de/theory/preprints.html#maclo
Análisis cuantitativo del daño causado por el gusano rosado de la India, Pectinophora gossypiella Saunders, en zonas algodoneras del Valle
La falta de información sobre el daño causado por el Gusano Rosado de la India, sobre su fluctuación según la fenología del cultivo y el manejo inadecuado que no permite hacer un control sanitario motivó este trabajo con el fín de evaluar el daño de P. gossypiella y la reación entre este y las normas producidas al desmontar algodoón. Además de evaluar el porcentaje de daño como índice del incremento de la población del Rosado de la India, se estimó la relación entre porcentaje de daños y porcentaje de normas producidas en el desmote. El porcentaje de daño en cápsula, estimado en seis períodos de evaluación, presenta una tendencia de tipo exponencial. Bajas infestaciones antes de los 130 días de emergencia del cultivo no son indicativos del potencial de daño del Rosado de la India en períodos posterioresAlgodó
Activation of microglia in specific hypothalamic nuclei and the cerebellum of adult rats exposed to neonatal overnutrition
Much attention has been drawn to the possible involvement of hypothalamic inflammation in the pathogenesis of metabolic disorders, especially in response to a high-fat diet. Microglia, the macrophages of the central nervous system, can be activated by proinflammatory signals resulting in the local production of specific interleukins and cytokines, which in turn could exacerbate the pathogenic process. Because obesity itself is considered to be a state of chronic inflammation, we evaluated whether being overweight results in microglial activation in the hypothalamus of rats on a normal diet. Accordingly, we used a model of neonatal overnutrition that entailed adjustment of litter size at birth (small litters: four pups/dam versus normal litters: 12 pups/dam) and resulted in a 15% increase in bodyweight and increased circulating leptin levels at postnatal day 60. Rats that were overnourished during neonatal life had an increased number of activated microglia in specific hypothalamic areas such as the ventromedial hypothalamus, which is an important site for metabolic control. However, this effect was not confined to the hypothalamus because significant microglial activation was also observed in the cerebellar white matter. There was no change in circulating tumour necrosis factor (TNF) α levels or TNFα mRNA levels in either the hypothalamus or cerebellum. Interleukin (IL)6 protein levels were higher in both the hypothalamus and cerebellum, with no change in IL6 mRNA levels. Because circulating IL6 levels were elevated, this rise in central IL6 could be a result of increased uptake. Thus, activation of microglia occurs in adult rats exposed to neonatal overnutrition and a moderate increase in weight gain on a normal diet, possibly representing a secondary response to systemic inflammation. Moreover, this activation could result in local changes in specific hypothalamic nuclei that in turn further deregulate metabolic homeostasi
Update of the recommendations for the determination of biomarkers in colorectal carcinoma: National Consensus of the Spanish Society of Medical Oncology and the Spanish Society of Pathology
In this update of the consensus of the Spanish Society of Medical Oncology (Sociedad Española de Oncología Médica SEOM) and the Spanish Society of Pathology (Sociedad Española de Anatomía Patológica SEAP), advances in the analysis of biomarkers in advanced colorectal cancer (CRC) as well as susceptibility markers of hereditary CRC and molecular biomarkers of localized CRC are reviewed. Recently published information on the essential determination of KRAS, NRAS and BRAF mutations and the convenience of determining the amplifcation of human epidermal growth factor receptor 2 (HER2), the expression of proteins in the DNA repair pathway and the study of NTRK fusions are also evaluated. From the pathological point of view, the importance of analysing the tumour budding and poorly diferentiated clusters, and its prognostic value in CRC is reviewed, as well as the impact of molecular lymph node analysis on lymph node staging in CRC. The incorporation of pan-genomic technologies, such as next-generation sequencing (NGS) and liquid biopsy in the clinical management of patients with CRC is also outlined. All these aspects are developed in this guide, which, like the previous one, will remain open to any necessary revision in the future
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