249 research outputs found
Changes in antioxidant enzymes during sunflower seed development
International audienc
Cache-Efficient Aggregation: Hashing Is Sorting
For decades researchers have studied the duality of hashing and sorting for the implementation of the relational operators, especially for efficient aggregation. Depending on the underlying hardware and software architecture, the specifically implemented algorithms, and the data sets used in the experiments, different authors came to different conclusions about which is the better approach. In this paper we argue that in terms of cache efficiency, the two paradigms are actually the same. We support our claim by showing that the complexity of hashing is the same as the complexity of sorting in the external memory model. Furthermore we make the similarity of the two approaches obvious by designing an algorithmic framework that allows to switch seamlessly between hashing and sorting during execution. The fact that we mix hashing and sorting routines in the same algorithmic framework allows us to leverage the advantages of both approaches and makes their similarity obvious. On a more practical note, we also show how to achieve very low constant factors by tuning both the hashing and the sorting routines to modern hardware. Since we observe a complementary dependency of the constant factors of the two routines to the locality of the input, we exploit our framework to switch to the faster routine where appropriate. The result is a novel relational aggregation algorithm that is cache-efficient---independently and without prior knowledge of input skew and output cardinality---, highly parallelizable on modern multi-core systems, and operating at a speed close to the memory bandwidth, thus outperforming the state-of-the-art by up to 3.7x
Analysis of Sugar Component of a Hot Water Extract from Arabidopsis thaliana Pollen Tubes Using GC-EI-MS
International audienceExtraction with hot water is the oldest and simplest method used to recover pectin from an alcohol insoluble residue extract, although this method has not been widely used for the cell wall analysis of pollen tube, a model used to study cell wall. This protocol described this method applied for pectin extraction from 6 h-old Arabidopsis pollen tubes followed by a sugar composition analysis by gas chromatography mass spectrometry
Pectin methylesterases and Arabidopsis pollen tube growth
International audienc
A new model depicting the role of PME during dehydration and germination of pollen grain
International audienc
Involvement of Pectin methylesterases in Arabidopsis pollen imbibitions and germination
International audienc
Does Transparent Hidden Matter Generate Optical Scintillation?
Stars twinkle because their light goes through the atmosphere. The same
phenomenon is expected when the light of extra-galactic stars goes through a
Galactic -- disk or halo -- refractive medium. Because of the large distances
involved here, the length and time scales of the optical intensity fluctuations
resulting from the wave distortions are accessible to the current technology.
In this paper, we discuss the different possible scintillation regimes and we
focus on the so-called strong diffractive regime that is likely to produce
large intensity contrasts. The critical relationship between the source angular
size and the intensity contrast in optical wavelengths is also discussed in
detail. We propose to monitor small extra-galactic stars every to search for intensity scintillation produced by molecular
hydrogen clouds. We discuss means to discriminate such hidden matter signal
from the foreground effects on light propagation. Appropriate observation of
the scintillation process described here should allow one to detect column
density stochastic variations in Galactic molecular clouds of order of , that is per
transverse distance.Comment: 16 pages, 10 eps figures. Accepted for publication in A&A. Minor
changes/additions : temporal coherence aspects; scintillation of a quasar in
tables 1 (reorganized) and 4; further details on the Local Interstellar
Mediu
Detecting the warm-hot intergalactic medium through X-ray absorption lines
The warm-hot intergalactic medium (WHIM) at temperatures 1E5-1E7 K is
believed to contain 30-50% of the baryons in the local universe. However, all
current X-ray detections of the WHIM at redshifts z>0 are of low statistical
significance (<=3sigma) and/or controversial. In this work, we aim to establish
the detection limits of current X-ray observatories and explore requirements
for next-generation X-ray telescopes for studying the WHIM through X-ray
absorption lines. We analyze all available grating observations of Mrk 421 and
obtain spectra with signal-to-noise ratio (S/N) of \sim90 and 190 per 50 mA
spectral bin from Chandra and XMM observations, respectively. Although these
spectra are two of the best ever collected with Chandra and XMM, we cannot
confirm the two WHIM systems reported by Nicastro et al. in 2005. Our bootstrap
simulations indicate that spectra with such high S/N cannot constrain the WHIM
with OVII column densities N(OVII)\sim1e15 cm^{-2} (corresponding to an
equivalent widths of 2.5 mA for a Doppler velocity of 50 km s^{-1}) at >=3sigma
significance level. The simulation results also suggest that it would take >60
Ms for Chandra and 140 Ms for XMM to measure the N(OVII) at >=4sigma from a
spectrum of a background QSO with flux of \sim0.2 mCrab (1 Crab = 2E-8 erg
s^{-1} cm^{-2} at 0.5-2 keV). Future X-ray pectrographs need to be equipped
with spectral resolution R \sim 4000 and effective area A>=100 cm^2 to
accomplish the similar constraints with an exposure time of \sim2 Ms and would
require \sim11 Ms to survey the 15 QSOs with flux \sim0.2 mCrab along which
clear intergalactic OVI absorbers have been detected.Comment: 13 pages with 9 figures and 2 tables, accepted for publication in Ap
Search for Eccentric Black Hole Coalescences during the Third Observing Run of LIGO and Virgo
Despite the growing number of confident binary black hole coalescences
observed through gravitational waves so far, the astrophysical origin of these
binaries remains uncertain. Orbital eccentricity is one of the clearest tracers
of binary formation channels. Identifying binary eccentricity, however, remains
challenging due to the limited availability of gravitational waveforms that
include effects of eccentricity. Here, we present observational results for a
waveform-independent search sensitive to eccentric black hole coalescences,
covering the third observing run (O3) of the LIGO and Virgo detectors. We
identified no new high-significance candidates beyond those that were already
identified with searches focusing on quasi-circular binaries. We determine the
sensitivity of our search to high-mass (total mass ) binaries
covering eccentricities up to 0.3 at 15 Hz orbital frequency, and use this to
compare model predictions to search results. Assuming all detections are indeed
quasi-circular, for our fiducial population model, we place an upper limit for
the merger rate density of high-mass binaries with eccentricities at Gpc yr at 90\% confidence level.Comment: 24 pages, 5 figure
Open data from the third observing run of LIGO, Virgo, KAGRA and GEO
The global network of gravitational-wave observatories now includes five
detectors, namely LIGO Hanford, LIGO Livingston, Virgo, KAGRA, and GEO 600.
These detectors collected data during their third observing run, O3, composed
of three phases: O3a starting in April of 2019 and lasting six months, O3b
starting in November of 2019 and lasting five months, and O3GK starting in
April of 2020 and lasting 2 weeks. In this paper we describe these data and
various other science products that can be freely accessed through the
Gravitational Wave Open Science Center at https://gwosc.org. The main dataset,
consisting of the gravitational-wave strain time series that contains the
astrophysical signals, is released together with supporting data useful for
their analysis and documentation, tutorials, as well as analysis software
packages.Comment: 27 pages, 3 figure
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