1,494 research outputs found
Economic analysis of potato, corn and wheat response to nitrogen and phosphorus application in the highlands of Ecuador
Cover title.Includes bibliographical references (page 39)
Detecting series periodicity with horizontal visibility graphs
The horizontal visibility algorithm has been recently introduced as a mapping
between time series and networks. The challenge lies in characterizing the
structure of time series (and the processes that generated those series) using
the powerful tools of graph theory. Recent works have shown that the visibility
graphs inherit several degrees of correlations from their associated series,
and therefore such graph theoretical characterization is in principle possible.
However, both the mathematical grounding of this promising theory and its
applications are on its infancy. Following this line, here we address the
question of detecting hidden periodicity in series polluted with a certain
amount of noise. We first put forward some generic properties of horizontal
visibility graphs which allow us to define a (graph theoretical) noise
reduction filter. Accordingly, we evaluate its performance for the task of
calculating the period of noisy periodic signals, and compare our results with
standard time domain (autocorrelation) methods. Finally, potentials,
limitations and applications are discussed.Comment: To be published in International Journal of Bifurcation and Chao
Coulomb's law corrections from a gauge-kinetic mixing
We study the static quantum potential for a gauge theory which includes the
mixing between the familiar photon and a second massive gauge
field living in the so-called hidden-sector . Our discussion is carried
out using the gauge-invariant but path-dependent variables formalism, which is
alternative to the Wilson loop approach. Our results show that the static
potential is a Yukawa correction to the usual static Coulomb potential.
Interestingly, when this calculation is done inside a superconducting box, the
Coulombic piece disappears leading to a screening phase.Comment: 4 page
A Spitzer Five-Band Analysis of the Jupiter-Sized Planet TrES-1
With an equilibrium temperature of 1200 K, TrES-1 is one of the coolest hot
Jupiters observed by {\Spitzer}. It was also the first planet discovered by any
transit survey and one of the first exoplanets from which thermal emission was
directly observed. We analyzed all {\Spitzer} eclipse and transit data for
TrES-1 and obtained its eclipse depths and brightness temperatures in the 3.6
{\micron} (0.083 % {\pm} 0.024 %, 1270 {\pm} 110 K), 4.5 {\micron} (0.094 %
{\pm} 0.024 %, 1126 {\pm} 90 K), 5.8 {\micron} (0.162 % {\pm} 0.042 %, 1205
{\pm} 130 K), 8.0 {\micron} (0.213 % {\pm} 0.042 %, 1190 {\pm} 130 K), and 16
{\micron} (0.33 % {\pm} 0.12 %, 1270 {\pm} 310 K) bands. The eclipse depths can
be explained, within 1 errors, by a standard atmospheric model with
solar abundance composition in chemical equilibrium, with or without a thermal
inversion. The combined analysis of the transit, eclipse, and radial-velocity
ephemerides gives an eccentricity , consistent
with a circular orbit. Since TrES-1's eclipses have low signal-to-noise ratios,
we implemented optimal photometry and differential-evolution Markov-chain Monte
Carlo (MCMC) algorithms in our Photometry for Orbits, Eclipses, and Transits
(POET) pipeline. Benefits include higher photometric precision and \sim10 times
faster MCMC convergence, with better exploration of the phase space and no
manual parameter tuning.Comment: 17 pages, Accepted for publication in Ap
ALMA Observations of the IRDC Clump G34.43+00.24 MM3: DNC/HNC Ratio
We have observed the clump G34.43+00.24 MM3 associated with an infrared dark
cloud in DNC =3--2, HNC =3--2, and NH =3--2 with the
Atacama Large Millimeter/submillimeter Array (ALMA). The NH emission is
found to be relatively weak near the hot core and the outflows, and its
distribution is clearly anti-correlated with the CS emission. This result
indicates that a young outflow is interacting with cold ambient gas. The
HNC emission is compact and mostly emanates from the hot core, whereas
the DNC emission is extended around the hot core. Thus, the DNC and HNC
emission traces warm regions near the protostar differently. The DNC emission
is stronger than the HNC emission toward most parts of this clump. The
DNC/HNC abundance ratio averaged within a area around the phase center is higher than 0.06. This ratio
is much higher than the value obtained by the previous single-dish observations
of DNC and HNC =1--0 (0.003). It seems likely that the DNC and
HNC emission observed with the single-dish telescope traces lower density
envelopes, while that observed with ALMA traces higher density and highly
deuterated regions. We have compared the observational results with
chemical-model results in order to investigate the behavior of DNC and HNC in
the dense cores. Taking these results into account, we suggest that the low
DNC/HNC ratio in the high-mass sources obtained by the single-dish observations
are at least partly due to the low filling factor of the high density regions.Comment: accepted to Ap
Toxicity of Neem's oil, a potential biocide against the invasive mussel Limnoperna fortunei (Dunker 1857)
The golden mussel Limnoperna fortunei (Dunker 1857) is one of the most distributed Nuisance Invasive Species (NIS) in South America, and a threat of great concern for the industry of the area. In this study, we carried out toxicity tests made with a Neem's oil solution with L. fortunei larvae and benthonic adults (7, 13 and 19 ± 1 mm). Tests with non-target species (Daphnia magna, Lactuca sativa and Cnesterodon decemmculatus) were also made with the aim to evaluate the potential toxicity of the Neem's solution in the environment. The LC100 of Neem's solution obtained for larvae was 500 μl/L, a value much higher than the one obtained for D. magna and C. decemmaculatus. Thus, we recommend that it should not be used in open waters. However, since the adults were killed in 72 h and the larvae in 24 h, this product can be used in closed systems, in man-made facilities.Facultad de Ciencias Naturales y Muse
Toxicity of Neem's oil, a potential biocide against the invasive mussel Limnoperna fortunei (Dunker 1857)
The golden mussel Limnoperna fortunei (Dunker 1857) is one of the most distributed Nuisance Invasive Species (NIS) in South America, and a threat of great concern for the industry of the area. In this study, we carried out toxicity tests made with a Neem's oil solution with L. fortunei larvae and benthonic adults (7, 13 and 19 ± 1 mm). Tests with non-target species (Daphnia magna, Lactuca sativa and Cnesterodon decemmculatus) were also made with the aim to evaluate the potential toxicity of the Neem's solution in the environment. The LC100 of Neem's solution obtained for larvae was 500 μl/L, a value much higher than the one obtained for D. magna and C. decemmaculatus. Thus, we recommend that it should not be used in open waters. However, since the adults were killed in 72 h and the larvae in 24 h, this product can be used in closed systems, in man-made facilities.Facultad de Ciencias Naturales y Muse
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