5,338 research outputs found
Título del cortometraje animado Hunter
This animated short film was done using 3D in order to delve into the field and because of
the interest in this method of animation.
This film tells a fictional history, set in a city inspired in Quito. The objectives was the
creation of a good product and entertain the audience. Another objective was to have an
interesting plot, not simple, monotonous or without interest. So I worked on how to tell and a
twist in the story, where the dam ends up being the survivor. And with one last twist in the
tale that draws attention.El video cuenta una historia ficticia, ambientada en una ciudad inspirada en Quito, con el
objetivo de lograr un buen producto y de entretener a la audiencia. Otro de los objetivos fue
el de tener una trama interesante, se trató de que no sea una historia simple, monótona, y sin
mayor interés. Por eso se ha trabajado en la manera de contarla y en un giro en la historia, en
donde la presa termina siendo el sobreviviente. Y con un último giro en la historia que llame
la atención del público. la razón de trabajarla en 3D fue el aprender más acerca de esta
manera de trabajar y por el interés personal que existe por el mismo
Aplicación de viguetas pretensadas para reducir las grietas en las losas aligeradas, de la edificación multifamiliar Varela en el distrito - Breña – Lima - 2019
El presente proyecto de investigación Aplicación de viguetas pretensadas para reducir las
grietas en las losas aligeradas en la edificación multifamiliar Varela en el Distrito de Breña
– Lima - 2019” tuvo como objetivo reducir las grietas generadas en las losas aligeradas del
sótano 3 de uso para estacionamientos en los paños 31 y 41, el proyecto fue diseñado para
usar un sistema compuesto de viguetas pretensadas prefabricadas y aligerantes, el estudio se
basó en un desarrollo técnico del diseño de la losa aligerada pretensada y compararlo con el
diseño del manual del proveedor para demostrar su impacto de sus características de
resistencias, durabilidad y calidad del mismo, para esto se tomó muestra de su diseño de
mezcla de la losa de compresión y características de la vigueta pretensada y comprobar su
comportamiento e impacto para determinar la reducción o eliminación de las grietas, el
método usado fue tipo de investigación aplicada de diseño experimental cuasi, debido a la
manipulación de la variable independiente para causar efecto a la variable dependiente, dando
como resultados casi similares al manual de diseño del proveedor y observándose los paños
en estudio en tiempo de 28 días del concreto endurecido sin la muestra de grietas,
concluyendo que la aplicación de viguetas pretensadas son de alta resistencias a compresión
y tracción, en lo económico con el sistema compuesto y comparado con lo tradicional de losa
aligerada de concreto reforzado, en costo se tiene un ahorro de casi el 20% menos
A Petal of the Sunflower: Photometry of the Stellar Tidal Stream in the Halo of Messier 63 (NGC 5055)
We present surface photometry of a very faint, giant arc feature in the halo
of the nearby spiral galaxy NGC 5055 (M63) that is consistent with being a part
of a stellar stream resulting from the disruption of a dwarf satellite galaxy.
This faint feature was first detected in early photographic studies by van der
Kruit (1979); more recently by Mart\'inez-Delgado et al. (2010) and as
presented in this work, the loop has been realized to be the result of a recent
minor merger through evidence obtained by deep images taken with a telescope of
only 0.16 m aperture. The stellar stream is confirmed in additional images
taken with the 0.5 m of the BlackBird Remote Observatory and the 0.8 m of the
McDonald Observatory. This low surface brightness structure around the disk of
the galaxy extends ~29 kpc from its center, with a projected width of 3.3 kpc.
The stream's morphology is consistent with that of the visible part of a
"great-circle" stellar stream originating from the accretion of a ~10^8 M_sun
dwarf satellite in the last few Gyr. The progenitor satellite's current
position and fate are not conclusive from our data. The color of the stream's
stars is consistent with Local Group dwarfs and is similar to the outer regions
of M63's disk and stellar halo. We detect other low surface brightness
"plumes"; some of these may be extended spiral features related to the galaxy's
complex spiral structure and others may be tidal debris associated with the
disruption of the galaxy's outer stellar disk as a result of the accretion
event. We differentiate between features related to the tidal stream and faint,
blue features in the outskirts of the galaxy's disk previously detected by the
GALEX satellite. With its highly warped HI gaseous disk (~20 deg), M63
represents one of several examples of an isolated spiral galaxy with a warped
disk showing strong evidence of an ongoing minor merger.Comment: 16 pages, 10 figures, 3 tables, Accepted for publication in The
Astronomical Journa
Nitrous oxide metabolism in nitrate-reducing bacteria: Physiology and regulatory mechanisms
Nitrous oxide (N2O) is an important greenhouse gas (GHG) with substantial global warming potential and also contributes to ozone depletion through photochemical nit- ric oxide (NO) production in the stratosphere. The negative effects of N2O on climate and stratospheric ozone make N2O mitigation an international challenge. More than 60% of global N2O emissions are emitted from agricultural soils mainly due to the appli- cation of synthetic nitrogen-containing fertilizers. Thus, mitigation strategies must be developed which increase (or at least do not negatively impact) on agricultural effi- ciency whilst decrease the levels of N2O released. This aim is particularly important in the context of the ever expanding population and subsequent increased burden on the food chain. More than two-thirds of N2O emissions from soils can be attributed to bacterial and fungal denitrification and nitrification processes. In ammonia-oxidizing bacteria, N2O is formed through the oxidation of hydroxylamine to nitrite. In denitrifiers, nitrate is reduced to N2 via nitrite, NO and N2O production. In addition to denitrification, respiratory nitrate ammonification (also termed dissimilatory nitrate reduction to ammonium) is another important nitrate-reducing mechanism in soil, responsible for the loss of nitrate and production of N2O from reduction of NO that is formed as a by-product of the reduction process. This review will synthesize our current understand- ing of the environmental, regulatory and biochemical control of N2O emissions by nitrate-reducing bacteria and point to new solutions for agricultural GHG mitigation
Fluorescent Excitation of Balmer Lines in Gaseous Nebulae: Case D
Nonionizing stellar continua are a potential source of photons for continuum pumping in the hydrogen Lyman transitions. In the environments where these transitions are optically thick, de-excitation occurs through higher series lines. As a result, the emitted flux in the affected lines has a fluorescent contribution in addition to the usual recombination one; in particular, Balmer emissivities are systematically enhanced above case B predictions. The effectiveness of such a mechanism in H II regions and the adequacy of photoionization models as a tool to study it are the two main focuses of this work. We find that photoionization models of H II regions illuminated by low-resolution (λ/δλ ≲ 1000) population synthesis models significantly overpredict the fluorescent contribution to the Balmer lines; the bias has typical values of the order of a few hundredths of a dex, with the exact figure depending on the parameters of the specific model and the simulated aperture. Conversely, photoionization models in which the nonionizing part of the continuum is omitted or is not transferred significantly underpredict the fluorescent contribution to the Balmer lines, producing a bias of similar amplitude in the opposite direction. Realistic estimations of the actual fluorescent fraction of the Balmer intensity require photoionization models in which the relevant portion of the stellar continuum is adequately represented, that is, its resolution is high in the region of the Lyman lines. In this paper, we carry out such an estimation and discuss the variations to be expected as the simulated observational setup and the stellar population\u27s parameters are varied. In all the cases explored, we find that fluorescent excitation provides a significant contribution to the total Balmer emissivity. We also show that differential fluorescent enhancement may produce line-of-sight differences in the Balmer decrement, mimicking interstellar extinction. Fluorescent excitation emerges from our study as a small but important mechanism for the enhancement of Balmer lines. As such, we recommend to take it into account in the abundance analysis of photoionized regions, particularly in the case of high-precision applications such as the determination of primordial helium
The Chemistry of the Trailing arm of the Sagittarius Dwarf Galaxy
We present abundances of C, O, Ti, and Fe for eleven M-giant stars in the
trailing tidal arm of the Sagittarius dwarf (Sgr). The abundances were derived
by comparing synthetic spectra with high-resolution infrared spectra obtained
with the Phoenix spectrograph on the Gemini South telescope. The targeted stars
are drawn from two regions of the Sgr trailing arm separated by 66 degrees (5
stars) and 132 degrees (6 stars) from the main body of Sgr. The trailing arm
provides a more direct diagnostic of the chemical evolution of Sgr compared to
the extensively phase-mixed leading arm.
Within our restricted sample of ~2-3 Gyr old stars, we find that the stream
material exhibits a significant metallicity gradient of -(2.4\pm0.3)x10^{-3}
dex / degree (-(9.4\pm1.1)x10^{-4} dex / kpc) away from the main body of Sgr.
The tidal disruption of Sgr is a relatively recently event. We therefore
interpret the presence of a metallicity gradient in the debris as indicative of
a similar gradient in the progenitor. The fact that such a metallicity gradient
survived for almost a Hubble time indicates that the efficiency of radial
mixing was very low in the Sgr progenitor.
No significant gradient is seen to exist in the [alpha/Fe] abundance ratio
along the trailing arm. Our results may be accounted for by a radial decrease
in star formation efficiency and/or radial increase in the efficiency of
galactic wind-driven metal loss in the chemical evolution of the Sgr
progenitor. The [Ti/Fe] and [O/Fe] abundance ratios observed within the stream
are distinct from those of the Galactic halo. We conclude that the fraction of
the intermediate to metal-rich halo population contributed by the recent
dissolution (<3 Gyr) of Sgr-like dwarf galaxies can not be substantial.Comment: 22 pages, 7 figures, ApJ accepte
Stellar over-densities in the halo: the extent of the Virgo over-density
We map the three dimensional extent of the Virgo Over-density by combining
distance information from RR Lyrae variables and projected spatial information
from SEKBO (Keller et al. 2008) and Sloan Digital Sky Survey (SDSS) DR6
photometry. The Virgo Over-density is seen to comprise two filaments 14.5 x 3
degrees and 10 x 3 degrees and a circular structure 3 degrees in diameter.
Together the three features span 38 degrees of right ascension and declinations
of +2 to -15 degrees. RR Lyrae variables place the two filamentary features at
heliocentric distances of 20 and 17 kpc respectively, with projected dimensions
of 5 x 1 kpc and 3 x 1 kpc.Comment: 6 pages, 5 figures, MNRAS accepte
The orientation and kinematics of inner tidal tails around dwarf galaxies orbiting the Milky Way
Using high-resolution collisionless N-body simulations we study the
properties of tidal tails formed in the immediate vicinity of a two-component
dwarf galaxy evolving in a static potential of the Milky Way (MW). The stellar
component of the dwarf is initially in the form of a disk and the galaxy is
placed on an eccentric orbit motivated by CDM-based cosmological simulations.
We measure the orientation, density and velocity distribution of the stars in
the tails. Due to the geometry of the orbit, in the vicinity of the dwarf,
where the tails are densest and therefore most likely to be detectable, they
are typically oriented towards the MW and not along the orbit. We report on an
interesting phenomenon of `tidal tail flipping': on the way from the pericentre
to the apocentre the old tails following the orbit are dissolved and new ones
pointing towards the MW are formed over a short timescale. We also find a tight
linear relation between the velocity of stars in the tidal tails and their
distance from the dwarf. Using mock data sets we demonstrate that if dwarf
spheroidal (dSph) galaxies in the vicinity of the MW are tidally affected their
kinematic samples are very likely contaminated by tidally stripped stars which
tend to artificially inflate the measured velocity dispersion. The effect is
stronger for dwarfs on their way from the peri- to the apocentre due to the
formation of new tidal tails after pericentre. Realistic mass estimates of dSph
galaxies thus require removal of these stars from kinematic samples.Comment: 8 pages, 7 figures, accepted for publication in MNRA
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