150 research outputs found
Functional linear regression with derivatives
We introduce a new model of linear regression for random functional inputs taking into account the first-order derivative of the data. We propose an estimation method that comes down to solving a special linear inverse problem. Our procedure tackles the problem through a double and synchronised penalisation. An asymptotic expansion of the mean square prevision error is given. The model and the method are applied to a benchmark dataset of spectrometric curves and compared with other functional models
Aggressiveness of eight Venturia inaequalis isolates virulent or avirulent to the major resistance gene Rvi6 on a non-Rvi6 apple cultivar
For sustainable management of scab-resistant apple cultivars, it is necessary to understand the role of aggressiveness in the adaptation of Venturia inaequalis populations and particularly the costs to the organism of acquiring additional virulence. The aims of the present study were (i) to identify the quantitative variables that are most important in determining the differences in aggressiveness among groups of V. inaequalis isolates, and (ii) to ascertain whether virulent and avirulent isolates of V. inaequalis differ significantly in aggressiveness. The aggressiveness of eight isolates that differed in their virulence to the major resistance gene Rvi6 was compared on the non-Rvi6 apple cv. Gala. Three components of aggressiveness, namely lesion density, the number of spores per square centimetre of leaf area, and the number of spores per lesion, were evaluated 21 days after inoculation, and the kinetics of lesion density over time were analysed in terms of maximum lesion density, length of latent period and rate of lesion appearance. On the second youngest but fully developed leaf at the time of inoculation, maximum lesion density in the virulent group was 20% lower and the latent period 7% longer, than in the avirulent group. However, the alternative hypothesis, namely that isolates had adapted to quantitative resistance present in cv. Gala depending on their cultivar of origin, could not be rejected. The analysis of the kinetics of lesion density by a non-linear mixed-effect model proved useful in the assessment of aggressiveness
Generalized linear model with functional predictors and their derivatives
The conditional expectation E(Y|X)E(Y|X) of a generalized functional linear model with scalar response YY is given by g{〈X,ϕ〉L2}g{〈X,ϕ〉L2} where XX and ϕϕ are functions defined in L2:=L2[0,1]L2:=L2[0,1]. Let us consider that XX belongs to the Sobolev space W:=W2,1[0,1]W:=W2,1[0,1] and denote X′X′ its derivative. In this paper we focus on an extension of the previous model where E(Y|X)E(Y|X) is given by g{〈X,β〉W+〈X′,γ〉L2}g{〈X,β〉W+〈X′,γ〉L2}. With a similar approach to Cardot and Sarda (2005) or Stone (1986) for generalized additive models, we propose estimators for the unknown parameters ββ, γγ and obtain their rate of convergence. We compare numerically the prediction performance of this new model with alternative models proposed in the literature
Estimation du paramètre des moyennes mobiles hilbertiennes
The moving average processes in a separable infinite-dimensional Hilbert space H, denoted by MAH ( 1 ) , is a H valued process ( X t , t ∈ Z ) satisfying the equation X t = ϵ t + l ( ϵ t − 1 ) where l is a compact operator in H and ( ϵ t ) a H valued strong white noise. In this Note we propose two estimators for l based on the moment equation of the process
SN 2013ab : A normal type IIP supernova in NGC 5669
We present densely-sampled ultraviolet/optical photometric and low-resolution
optical spectroscopic observations of the type IIP supernova 2013ab in the
nearby (24 Mpc) galaxy NGC 5669, from 2 to 190d after explosion.
Continuous photometric observations, with the cadence of typically a day to one
week, were acquired with the 1-2m class telescopes in the LCOGT network, ARIES
telescopes in India and various other telescopes around the globe. The light
curve and spectra suggest that the SN is a normal type IIP event with a plateau
duration of days with mid plateau absolute visual magnitude of
-16.7, although with a steeper decline during the plateau (0.92 mag 100 d in band) relative to other archetypal SNe of similar brightness.
The velocity profile of SN 2013ab shows striking resemblance with those of SNe
1999em and 2012aw. Following the Rabinak & Waxman (2011) prescription, the
initial temperature evolution of the SN emission allows us to estimate the
progenitor radius to be 800 R, indicating that the SN
originated from a red supergiant star. The distance to the SN host galaxy is
estimated to be 24.3 Mpc from expanding photosphere method (EPM). From our
observations, we estimate that 0.064 M of Ni was synthesized
in the explosion. General relativistic, radiation hydrodynamical modeling of
the SN infers an explosion energy of erg, a progenitor
mass (at the time of explosion) of M and an initial radius
of R.Comment: 22 pages, 18 figures, 5 tables. Accepted for publication in MNRA
A Continuous Time-and-State Epidemic Model Fitted to Ordinal Categorical Data Observed on a Lattice at Discrete Times
We consider a spatio-temporal model to describe the spread of apple scab within an orchard composed of several plots. The model is defined on a regular lattice and evolves in continuous time. Based on ordinal categorical data observed only at some discrete instants, we adopt a continuous-time approach and apply a Bayesian framework for estimating unknown parameters
Self-Enrichment in Globular Clusters: Is There a Role for the Super-Asymptotic Giant Branch Stars?
In four globular clusters (GCs) a non negligible fraction of stars can be
interpreted only as a very helium rich population. The evidence comes from the
presence of a "blue" main sequence in Cen and NGC 2808, and from the
the very peculiar horizontal branch morphology in NGC 6441 and NGC 6388.
Although a general consensus is emerging on the fact that self--enrichment is a
common feature among GCs, the helium content required for these stars is
Y\simgt0.35, and it is difficult to understand how it can be produced without
any --or, for Cen, without a considerable--associated metal
enhancement. We examine the possible role of super--AGB stars, and show that
they may provide the required high helium. However, the ejecta of the most
massive super--AGBs show a global CNO enrichment by a factor of 4, due
to the dredge--out process occurring at the second dredge up stage. If these
clusters show no evidence for this CNO enrichment, we can rule out that at
least the most massive super--AGBs evolve into O--Ne white dwarfs and take part
in the formation of the second generation stars. This latter hypothesis may
help to explain the high number of neutron stars present in GCs. The most
massive super--AGBs would in fact evolve into electron--capture supernovae.
Their envelopes would be easily ejected out of the cluster, but the remnant
neutron stars remain into the clusters, thanks to their small supernova natal
kicks.Comment: version accepted for publication in The Astrophysical Journal Letter
SN 2015ba: A type IIP supernova with a long plateau
We present optical photometry and spectroscopy from about a week after
explosion to 272 d of an atypical Type IIP supernova, SN 2015ba, which
exploded in the edge-on galaxy IC 1029. SN 2015ba is a luminous event with an
absolute V-band magnitude of -17.10.2 mag at 50 d since explosion and has
a long plateau lasting for 123 d. The distance to the SN is estimated to
be 34.80.7 Mpc using the expanding photosphere and standard candle
methods. High-velocity H-Balmer components constant with time are observed in
the late-plateau phase spectra of SN 2015ba, which suggests a possible role of
circumstellar interaction at these phases. Both hydrodynamical and analytical
modelling suggest a massive progenitor of SN 2015ba with a pre-explosion mass
of 24-26 M. However, the nebular spectra of SN 2015ba exhibit
insignificant levels of oxygen, which is otherwise expected from a massive
progenitor. This might be suggestive of the non-monotonical link between O-core
masses and the zero-age main-sequence mass of pre-supernova stars and/or
uncertainties in the mixing scenario in the ejecta of supernovae.Comment: 42 pages, 7 pages Appendix, 20 figures, 10 tables, Accepted for
publication in MNRAS, 14-June-201
Breeding for carrot resistance to Alternaria dauci without compromising taste
Developing carrot varieties highly resistant to Alternaria dauci is a top priority for breeders. Meanwhile, consumers are increasingly demanding as regards final product quality, particularly taste. Bitterness is one of the five common taste sensations, but it is rejected by most carrot consumers. Therefore, providing tools for efficient plant breeding of resistant, low bitter carrots would be helpful. While resistance QTLs (rQTLs) have already been identified for carrot resistance to A. dauci, the genetic control and mapping of the metabolites involved in bitterness perception have not been addressed so far. We identified the metabolites most involved in bitterness by combining chemical and sensory analyses of a set of resistant and susceptible carrot genotypes grown in different environments. We evaluated their genetic control and heritability in a segregating F2:3 population over 2Â years of field trials and searched for colocalizations between rQTLs and metabolite QTLs (mQTLs) to evaluate the link between bitterness and resistance traits. Our results suggest that it is possible to increase resistance while favoring low bitter varieties by selecting genomic regions involved in the expression of one or the other trait and counter-selecting others when r- and mQTL colocalization is unfavorable
Nickel-Rich Outflows Produced by the Accretion-Induced Collapse of White Dwarfs: Lightcurves and Spectra
The accretion-induced collapse (AIC) of a white dwarf to form a neutron star
can leave behind a rotationally supported disk with mass of up to ~ 0.1 M_sun.
The disk is initially composed of free nucleons but as it accretes and spreads
to larger radii, the free nucleons recombine to form helium, releasing
sufficient energy to unbind the remaining disk. Most of the ejected mass fuses
to form Ni56 and other iron group elements. We present spherically symmetric
radiative transfer calculations of the transient powered by the radioactive
heating of this ejecta. For an ejecta mass of 1e-2 M_sun (3e-3 M_sun), the
lightcurve peaks after <~ 1 day with a peak bolometric luminosity ~ 2e41 erg/s
(~ 5e40 erg/s), i.e., a "kilonova"; the decay time is ~ 4 (2) days. Overall,
the spectra redden with time reaching U-V ~ 4 after ~ 1 day; the optical colors
(B-V) are, however, somewhat blue. Near the peak in the lightcurve, the spectra
are dominated by Doppler broadened Nickel features, with no distinct spectral
lines present. At ~ 3-5 days, strong Calcium lines are present in the infrared,
although the Calcium mass fraction is only ~ 1e-4.5. If rotationally supported
disks are a common byproduct of AIC, current and upcoming transient surveys
such as the Palomar Transient Factory should detect a few AIC per year for an
AIC rate of ~ 1e-2 of the Type Ia rate. We discuss ways of distinguishing AIC
from other rapid, faint transients, including .Ia's and the ejecta from binary
neutron star mergers.Comment: 9 pages, 4 figures, 1 table, now accepted to MNRA
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