634 research outputs found
On the usefulness of finding charts Or the runaway carbon stars of the Blanco & McCarthy field 37
We have been recently faced with the problem of cross--identifying stars
recorded in historical catalogues with those extracted from recent fully
digitized surveys (such as DENIS and 2MASS). Positions mentioned in the old
catalogues are frequently of poor precision, but are generally accompanied by
finding charts where the interesting objects are flagged. Those finding charts
are sometimes our only link with the accumulated knowledge of past literature.
While checking the identification of some of these objects in several
catalogues, we had the surprise to discover a number of discrepancies in recent
works.The main reason for these discrepancies was generally the blind
application of the smallest difference in position as the criterion to identify
sources from one historical catalogue to those in more recent surveys. In this
paper we give examples of such misidentifications, and show how we were able to
find and correct them.We present modern procedures to discover and solve
cross--identification problems, such as loading digitized images of the sky
through the Aladin service at CDS, and overlaying entries from historical
catalogues and modern surveys. We conclude that the use of good finding charts
still remains the ultimate (though time--consuming) tool to ascertain
cross--identifications in difficult cases.Comment: 4 pages, 1 figure, accepted by A&
Identification and geographic distribution of genetic groups of Erysiphe necator in Chilean vineyards
The grapevine powdery mildew, caused by the biotrophic fungus Erysiphe necator, is one of the most important diseases of this crop in Chile. We converted existing single nucleotide polymorphisms in ÎČ-tubulin, rDNA intergenic spacer region 1 and eburicol 14-α-demethylase into three cleaved amplified polymorphic sequences (CAPS). These CAPS markers were used for the genetic characterization of Erysiphe necator isolates collected on clusters of Vitis vinifera cv. 'Cabernet Sauvignon' in 23 vineyards across Chile. Among the 105 Chilean isolates analyzed, 103 revealed to belong to genetic group B and 2 to genetic group A. These results correspond to the first report of the presence of genetic groups A and B of E. necator in Chile
Improved Procedures for Purification of the Bandeiraea simplicifolia I Isolectins and Bandeiraea simplicifolia II Lectin by Affinity Chromatography
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66350/1/j.1432-1033.1980.tb07197.x.pd
A simple catch: Fluctuations enable hydrodynamic trapping of microrollers by obstacles
It is known that obstacles can hydrodynamically trap bacteria and synthetic microswimmers in orbits, where the trapping time heavily depends on the swimmer flow field and noise is needed to escape the trap. Here, we use experiments and simulations to investigate the trapping of microrollers by obstacles. Microrollers are rotating particles close to a bottom surface, which have a prescribed propulsion direction imposed by an external rotating magnetic field. The flow field that drives their motion is quite different from previously studied swimmers. We found that the trapping time can be controlled by modifying the obstacle size or the colloid-obstacle repulsive potential. We detail the mechanisms of the trapping and find two remarkable features: The microroller is confined in the wake of the obstacle, and it can only enter the trap with Brownian motion. While noise is usually needed to escape traps in dynamical systems, here, we show that it is the only means to reach the hydrodynamic attractor.âla Caixaâ Foundation (ID 100010434), fellowship LCF/BQ/-PI20/11760014.
The European Unionâs Horizon 2020 research and innovation programme under the Marie SkĆodowska-Curie
grant agreement no. 847648
High density plasma deposition of device quality silicon nitride. II. Effects of thickness on the electrical properties
Dielectric behavior of SiNx films, fabricated by microwave electron cyclotron resonance discharge, has been studied as a function of film thickness on the basis of the currentâvoltage and the capacitanceâvoltage characteristics. In the thickness range (20 nm,d,80 nm), the resistivity and the critical field for SiNx were found not to be sensitive to the film thickness ~d! and which was opposite to strong dependence of the dynamic dielectric constant e d on thickness. To explain the e d behavior as a function of d, a model based on trapped space charge effects is proposed. The dominant mode of electronic conduction, determined from J âE1/2 curves and Arrhenius plots of leakage current, appears to be PooleâFrenkel emission only for thicker films (d.20 nm). Finally, the spatial profile of fixed charges reveals that SiNx /Si interface has a much greater concentration of defects than the bulk film
Climate dependent contrast in surface mass balance in East Antarctica over the past 216 ka
ABSTRACTDocumenting past changes in the East Antarctic surface mass balance is important to improve ice core chronologies and to constrain the ice-sheet contribution to global mean sea-level change. Here we reconstruct past changes in the ratio of surface mass balance (SMB ratio) between the EPICA Dome C (EDC) and Dome Fuji (DF) East Antarctica ice core sites, based on a precise volcanic synchronization of the two ice cores and on corrections for the vertical thinning of layers. During the past 216 000 a, this SMB ratio, denoted SMBEDC/SMBDF, varied between 0.7 and 1.1, being small during cold periods and large during warm periods. Our results therefore reveal larger amplitudes of changes in SMB at EDC compared with DF, consistent with previous results showing larger amplitudes of changes in water stable isotopes and estimated surface temperature at EDC compared with DF. Within the last glacial inception (Marine Isotope Stages, MIS-5c and MIS-5d), the SMB ratio deviates by up to 0.2 from what is expected based on differences in water stable isotope records. Moreover, the SMB ratio is constant throughout the late parts of the current and last interglacial periods, despite contrasting isotopic trends.This is the accepted manuscript. It is currently embargoed pending publication
Developing a western Siberia reference site for tropospheric water vapour isotopologue observations obtained by different techniques (in situ and remote sensing)
Water stable isotopologues provide integrated tracers of the atmospheric
water cycle, affected by changes in air mass origin, non-convective
and convective processes and continental recycling. Novel remote
sensing and in situ measuring techniques have recently offered
opportunities for monitoring atmospheric water vapour isotopic
composition. Recently developed infrared laser spectrometers allow for
continuous in situ measurements of surface water vapour
δD<sub>v</sub> and
δ<sup>18</sup>O<sub>v</sub>. So far, very few intercomparisons
of measurements conducted using different techniques have been
achieved at a given location, due to difficulties intrinsic to the
comparison of integrated with local measurements. Nudged simulations
conducted with high-resolution isotopically enabled general circulation models (GCMs) provide
a consistent framework for comparison with the different types of
observations. Here, we compare simulations conducted with the
ECHAM5-wiso model with two types of water vapour isotopic data
obtained during summer 2012 at the forest site of Kourovka, western
Siberia: hourly ground-based FTIR total atmospheric columnar
δD<sub>v</sub> amounts, and in situ hourly Picarro
δD<sub>v</sub> measurements. There is an excellent
correlation between observed and predicted
δD<sub>v</sub> at surface while the comparison between
water column values derived from the model compares well with FTIR
estimates
Identification of the First Oomycete Mating-type Locus Sequence in the Grapevine Downy Mildew Pathogen, Plasmopara viticola
Mating types are self-incompatibility systems that promote outcrossing in plants, fungi, and oomycetes. Mating-type genes have been widely studied in plants and fungi but have yet to be identified in oomycetes, eukaryotic organisms closely related to brown algae that cause many destructive animal and plant diseases. We identified the mating-type locus of Plasmopara viticola, the oomycete responsible for grapevine downy mildew, one of the most damaging grapevine diseases worldwide. Using a genome-wide association approach, we identified a 570-kb repeat-rich non-recombining region controlling mating types, with two highly divergent alleles. We showed that one mating type was homozygous, whereas the other was heterozygous at this locus. The mating-type locus encompassed 40 genes, including one encoding a putative hormone receptor. Functional studies will, however, be required to validate the function of these genes and find the actual determinants of mating type. Our findings have fundamental implications for our understanding of the evolution of mating types, as they reveal a unique determinism involving an asymmetry of heterozygosity, as in sex chromosomes and unlike other mating-type systems. This identification of the mating-type locus in such an economically important crop pathogen also has applied implications, as outcrossing facilitates rapid evolution and resistance to harsh environmental conditions
Cr/Sc multilayer radiator for parametric EUV radiation in "water-window" spectral range
The results of experimental investigation of parametric radiation generated by 5.7 MeV electrons in a multilayer structure consisting of 100 Cr/Sc bi-layers deposited on a Si[3]N[4] membrane are presented. The multilayer structure was specially created for generation of parametric radiation with photon energy in "water-window" spectral range. First test measurements of angular distributions of radiation have been done and discussed
Internal frequency conversion extreme ultraviolet interferometer using mutual coherence properties of two high-order-harmonic sources
International audienceWe report on an innovative two-dimensional imaging extreme ultraviolet (XUV) interferometer operating at 32 nm based on the mutual coherence of two laser high order harmonics (HOH) sources, separately generated in gas. We give the first evidence that the two mutually coherent HOH sources can be produced in two independent spatially separated gas jets, allowing for probing centimeter-sized objects. A magnification factor of 10 leads to a micron resolution associated with a subpicosecond temporal resolution. Single shot interferograms with a fringe visibility better than 30% are routinely produced. As a test of the XUV interferometer, we measure a maximum electronic density of 3Ă10^20âcm^â3 1.1 ns after the creation of a plasma on aluminum target
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