766 research outputs found
The Genetic Basis of Tomato Aroma
Tomato (Solanum lycopersicum L.) aroma is determined by the interaction of volatile compounds (VOCs) released by the tomato fruits with receptors in the nose, leading to a sensorial impression, such as “sweet”, “smoky”, or “fruity” aroma. Of the more than 400 VOCs released by tomato fruits, 21 have been reported as main contributors to the perceived tomato aroma. These VOCs can be grouped in five clusters, according to their biosynthetic origins. In the last decades, a vast array of scientific studies has investigated the genetic component of tomato aroma in modern tomato cultivars and their relatives. In this paper we aim to collect, compare, integrate and summarize the available literature on flavour-related QTLs in tomato. Three hundred and 5ifty nine (359) QTLs associated with tomato fruit VOCs were physically mapped on the genome and investigated for the presence of potential candidate genes. This review makes it possible to (i) pinpoint potential donors described in literature for specific traits, (ii) highlight important QTL regions by combining information from different populations, and (iii) pinpoint potential candidate genes. This overview aims to be a valuable resource for researchers aiming to elucidate the genetics underlying tomato flavour and for breeders who aim to improve tomato aroma.</p
The Milky Way's circular velocity curve between 4 and 14 kpc from APOGEE data
We measure the Milky Way's rotation curve over the Galactocentric range 4 kpc
<~ R <~ 14 kpc from the first year of data from the Apache Point Observatory
Galactic Evolution Experiment (APOGEE). We model the line-of-sight velocities
of 3,365 stars in fourteen fields with b = 0 deg between 30 deg < l < 210 deg
out to distances of 10 kpc using an axisymmetric kinematical model that
includes a correction for the asymmetric drift of the warm tracer population
(\sigma_R ~ 35 km/s). We determine the local value of the circular velocity to
be V_c(R_0) = 218 +/- 6 km/s and find that the rotation curve is approximately
flat with a local derivative between -3.0 km/s/kpc and 0.4 km/s/kpc. We also
measure the Sun's position and velocity in the Galactocentric rest frame,
finding the distance to the Galactic center to be 8 kpc < R_0 < 9 kpc, radial
velocity V_{R,sun} = -10 +/- 1 km/s, and rotational velocity V_{\phi,sun} =
242^{+10}_{-3} km/s, in good agreement with local measurements of the Sun's
radial velocity and with the observed proper motion of Sgr A*. We investigate
various systematic uncertainties and find that these are limited to offsets at
the percent level, ~2 km/s in V_c. Marginalizing over all the systematics that
we consider, we find that V_c(R_0) 99% confidence. We find an
offset between the Sun's rotational velocity and the local circular velocity of
26 +/- 3 km/s, which is larger than the locally-measured solar motion of 12
km/s. This larger offset reconciles our value for V_c with recent claims that
V_c >~ 240 km/s. Combining our results with other data, we find that the Milky
Way's dark-halo mass within the virial radius is ~8x10^{11} M_sun.Comment: submitted to Ap
Substructure Boosts to Dark Matter Annihilation from Sommerfeld Enhancement
The recently introduced Sommerfeld enhancement of the dark matter
annihilation cross section has important implications for the detection of dark
matter annihilation in subhalos in the Galactic halo. In addition to the boost
to the dark matter annihilation cross section from the high densities of these
subhalos with respect to the main halo, an additional boost caused by the
Sommerfeld enhancement results from the fact that they are kinematically colder
than the Galactic halo. If we further believe the generic prediction of CDM
that in each subhalo there is an abundance of substructure which is
approximately self-similar to that of the Galactic halo, then I show that
additional boosts coming from the density enhancements of these small
substructures and their small velocity dispersions enhance the dark matter
annihilation cross section even further. I find that very large boost factors
( to ) are obtained in a large class of models. The implications of
these boost factors for the detection of dark matter annihilation from dwarf
Spheroidal galaxies in the Galactic halo are such that, generically, they
outshine the background gamma-ray flux and are detectable by the Fermi
Gamma-ray Space Telescope.Comment: PRD in pres
The rin, nor and Cnr spontaneous mutations inhibit tomato fruit ripening in additive and epistatic manners
Tomato fruit ripening is regulated by transcription factors (TFs), their downstream effector genes, and the ethylene biosynthesis and signalling pathway. Spontaneous non-ripening mutants ripening inhibitor (rin), non-ripening (nor) and Colorless non-ripening (Cnr) correspond with mutations in or near the TF-encoding genes MADS-RIN, NAC-NOR and SPL-CNR, respectively. Here, we produced heterozygous single and double mutants of rin, nor and Cnr and evaluated their functions and genetic interactions in the same genetic background. We showed how these mutations interact at the level of phenotype, individual effector gene expression, and sensory and quality aspects, in a dose-dependent manner. Rin and nor have broadly similar quantitative effects on all aspects, demonstrating their additivity in fruit ripening regulation. We also found that the Cnr allele is epistatic to rin and nor and that its pleiotropic effects on fruit size and volatile production, in contrast to the well-known dominant effect on ripening, are incompletely dominant, or recessive.</p
N=1,2 supersymmetric vacua of IIA supergravity and SU(2) structures
We consider backgrounds of (massive) IIA supergravity of the form of a warped
product , where is a six-dimensional compact
manifold and is or a four-dimensional Minkowski space. We
analyse conditions for and supersymmetry on
manifolds of SU(2) structure. We prove the absence of solutions in certain
cases.Comment: 24 pages; v2: reference adde
Thick disk kinematics from RAVE and the solar motion
Radial velocity surveys such as the Radial Velocity Experiment (RAVE) provide
us with measurements of hundreds of thousands of nearby stars most of which
belong to the Galactic thin, thick disk or halo. Ideally, to study the Galactic
disks (both thin and thick) one should make use of the multi-dimensional
phase-space and the whole pattern of chemical abundances of their stellar
populations. In this paper, with the aid of the RAVE Survey, we study the thin
and thick disks of the Milky Way, focusing on the latter. We present a
technique to disentangle the stellar content of the two disks based on the
kinematics and other stellar parameters such as the surface gravity of the
stars. Using the Padova Galaxy Model, we checked the ability of our method to
correctly isolate the thick disk component from the Galaxy mixture of stellar
populations. We introduce selection criteria in order to clean the observed
radial velocities from the Galactic differential rotation and to take into
account the partial sky coverage of RAVE. We developed a numerical technique to
statistically disentangle thin and thick disks from their mixture. We deduce
the components of the solar motion relative to the Local Standard of Rest (LSR)
in the radial and vertical direction, the rotational lag of the thick disk
component relative to the LSR, and the square root of the absolute value of the
velocity dispersion tensor for the thick disk alone. The analysis of the thin
disk is presented in another paper. We find good agreement with previous
independent parameter determinations. In our analysis we used photometrically
determined distances. In the Appendix we show that similar values can be found
for the thick disk alone as derived in the main sections of our paper even
without the knowledge of photometric distances.Comment: accepted on A&A, please see companion paper "THIN disk kinem...
Photometric redshifts and quasar probabilities from a single, data-driven generative model
We describe a technique for simultaneously classifying and estimating the
redshift of quasars. It can separate quasars from stars in arbitrary redshift
ranges, estimate full posterior distribution functions for the redshift, and
naturally incorporate flux uncertainties, missing data, and multi-wavelength
photometry. We build models of quasars in flux-redshift space by applying the
extreme deconvolution technique to estimate the underlying density. By
integrating this density over redshift one can obtain quasar flux-densities in
different redshift ranges. This approach allows for efficient, consistent, and
fast classification and photometric redshift estimation. This is achieved by
combining the speed obtained by choosing simple analytical forms as the basis
of our density model with the flexibility of non-parametric models through the
use of many simple components with many parameters. We show that this technique
is competitive with the best photometric quasar classification
techniques---which are limited to fixed, broad redshift ranges and high
signal-to-noise ratio data---and with the best photometric redshift techniques
when applied to broadband optical data. We demonstrate that the inclusion of UV
and NIR data significantly improves photometric quasar--star separation and
essentially resolves all of the redshift degeneracies for quasars inherent to
the ugriz filter system, even when included data have a low signal-to-noise
ratio. For quasars spectroscopically confirmed by the SDSS 84 and 97 percent of
the objects with GALEX UV and UKIDSS NIR data have photometric redshifts within
0.1 and 0.3, respectively, of the spectroscopic redshift; this amounts to about
a factor of three improvement over ugriz-only photometric redshifts. Our code
to calculate quasar probabilities and redshift probability distributions is
publicly available
The SDSS-III Baryon Oscillation Spectroscopic Survey: Quasar Target Selection for Data Release Nine
The SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS), a five-year
spectroscopic survey of 10,000 deg^2, achieved first light in late 2009. One of
the key goals of BOSS is to measure the signature of baryon acoustic
oscillations in the distribution of Ly-alpha absorption from the spectra of a
sample of ~150,000 z>2.2 quasars. Along with measuring the angular diameter
distance at z\approx2.5, BOSS will provide the first direct measurement of the
expansion rate of the Universe at z > 2. One of the biggest challenges in
achieving this goal is an efficient target selection algorithm for quasars over
2.2 < z < 3.5, where their colors overlap those of stars. During the first year
of the BOSS survey, quasar target selection methods were developed and tested
to meet the requirement of delivering at least 15 quasars deg^-2 in this
redshift range, out of 40 targets deg^-2. To achieve these surface densities,
the magnitude limit of the quasar targets was set at g <= 22.0 or r<=21.85.
While detection of the BAO signature in the Ly-alpha absorption in quasar
spectra does not require a uniform target selection, many other astrophysical
studies do. We therefore defined a uniformly-selected subsample of 20 targets
deg^-2, for which the selection efficiency is just over 50%. This "CORE"
subsample will be fixed for Years Two through Five of the survey. In this paper
we describe the evolution and implementation of the BOSS quasar target
selection algorithms during the first two years of BOSS operations. We analyze
the spectra obtained during the first year. 11,263 new z>2.2 quasars were
spectroscopically confirmed by BOSS. Our current algorithms select an average
of 15 z > 2.2 quasars deg^-2 from 40 targets deg^-2 using single-epoch SDSS
imaging. Multi-epoch optical data and data at other wavelengths can further
improve the efficiency and completeness of BOSS quasar target selection.
[Abridged]Comment: 33 pages, 26 figures, 12 tables and a whole bunch of quasars.
Submitted to Ap
The Galactic Halo in Mixed Dark Matter Cosmologies
A possible solution to the small scale problems of the cold dark matter (CDM)
scenario is that the dark matter consists of two components, a cold and a warm
one. We perform a set of high resolution simulations of the Milky Way halo
varying the mass of the WDM particle () and the cosmic dark matter
mass fraction in the WDM component (). The scaling ansatz
introduced in combined analysis of LHC and astroparticle searches postulates
that the relative contribution of each dark matter component is the same
locally as on average in the Universe (e.g. ). Here we find however, that the normalised local WDM fraction ( / ) depends strongly on for 1 keV. Using the scaling ansatz can therefore introduce significant
errors into the interpretation of dark matter searches. To correct this issue a
simple formula that fits the local dark matter densities of each component is
provided.Comment: 19 pages, 10 figures, accepted for publication in JCA
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